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p0300


DJRATEDR

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i've been getting code "p0300" misfire. car's running like crap! i pulled the wires off the 1st coil from the left (1-4) then started the car ... coil started to arc but then stopped. 1st starts arcing when i start the car but quickly stops. i put the wires back on and did the same thing with the 2nd from the left (6-7) no arcing. the other 2 coils fire fine. i also checked for voltage with the coils off and it is getting power when the key is in the "on" position.

any suggestions - ideas?

thanks for your time.

oh yeah ... i switched the packs around to make sure it wasn't a bad coil pack and also had a new coil pack, but my 1-4 and 6-7 aren't firing.

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You didn't give the miles, but as a 1998 it's 12 years old. It's time for plugs and wires. I would check the coil resistances, primary and secondary, also.

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-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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Jim, we have another member with the same problem, he replaced his engine, I can't find the link

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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the car has 199,000+ miles on it. the wires and plugs were recently replaced last year as well as the (1-4) coil. again, no spark from that one and on the first coil (6-7) it only sparks for a few seconds when you first start the car. the arcing (if it wasn't clear the first time) was from the actual coil packs - not the plug end.

i'm a bit mechanically inclined as well as electronically, but when you say "check the resistance of the coils on the primary and secondary" ... i'm a bit confused? also, what should the resistance be? it is the coils that send current to the plugs and to the engine right or vice-versa? when i checked the voltage on the 2 prongs with the coils removed, the first on from the left read 11.9 volts with the key on the "on" position. the second coil read 9.7 volts.

i'm so clueless as to what could be causing this. please help.

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....i'm a bit mechanically inclined as well as electronically, but when you say "check the resistance of the coils on the primary and secondary" ... i'm a bit confused? also, what should the resistance be?

Read through this....

http://caddyinfo.ipbhost.com/index.php?showtopic=16967

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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The ignition in modern cars like the Northstar is interesting. The PCM takes inputs from the crank and cam sensors and keeps track of the RPM, crank position, manifold vacuum, and throttle position, and performs all the functions of the old-fashioned distributor, centrifugal spark advance, vacuum spark advance, and cap and rotor. It passes this data, including spark timing, to the ignition module which performs the function of the points and condenser, and fires the four coils at the right timing for their respective two cylinders. If the car runs fine at any time, or runs with just a miss, everything is good except the ignition module, coils, wires and plugs, which must be checked individually.

The coils are similar to old-fashioned coils, except that the high-voltage winding on old fashioned coils is grounded on one end and goes to the distributor hight voltage wire on the other terminal. On the Northstar (and most other) coils, both ends of the high-voltage winding go to plug wires. Later models have coil-on-plug, which is eight coils that ground one end of the high-voltage winding and the other is right on the spark plug, but that was after 1998 (2004?)

So, your coils have large-wire low-voltage windings that go to the ignition module, and tiny-wire high-voltage windings that go to your plugs, just like older coils. When coils go bad, windings get disconnected, shorted, or arc over to each other, and very oten you can tell what is what with an ohmmeter.

I'm looking around in the 1997 FSM. The spark plug wire resistance should be less than 15,000 Ohms. The spark plug resistance (from the plug wire terminal to the center electrode) should be 10,000 Ohms or more. There should be an open circuit (infinity Ohms) across the spark plug from the plug wire terminal to the threads, and between the coil high-voltage terminals and ground. (Page 6-674)

The coils fire cylinder pairs 1&4, 2&5, 6&6 and 3&8 (page 6-673). You check the secondary resistance by using the Ohmmeter across the high-voltage outputs of the coil. Check them all and if any of them are out-of-line with the others, that coil is bad. I've seen a value to look for but don't turn it up this afternoon.

The 1997 FSM addresses misses and cutouts pages 6-637 through 6-639. Without repeating the whole thing, here are the steps it recommends:

  • Run the OBD codes and address the codes you see first, particularly the PCM codes.
  • Check the service bulletins. That's very much like posting your question on Caddyinfo and asking all the guys here about your problem, which you've done.
  • Do a visual check. Look for problems with the plug wires, the way they are routed under the beauty cover, and obvious signs of problems. If the car misses or stumbles at idle, look at it in the dark with the beauty cover off. Look for carbon tracking on the coils where arcing has occurred.
  • With a scan tool, check for long-term rich or lean mixture. Deal with that and see if it solves the problem. Without a scan tool, you can make sure that the air cleaner element is clean or new, and that the air duct from the air cleaner to the throttle body is not dented or collapsed, and that there is nothing in the throttle body, like a bird.
  • Check for vacuum leaks. This can be a cracked, broken or cut vacuum line, a stuck PCV valve, a loose or missing oil filler cap or dipstick, or a manifold leak.
  • Make sure the IAC motor is OK and the idle speed is correct. If your car misses while driving, the IAC isn't causing that.
  • Go over the throttle body. Look for a missing adjustment screw plug, excessive deposits in the IAC passage and on the IAC pintle or on the throttle bore or throttle plate.
  • Check out the fuel injector connections. Make sure that they are all on the right cylinders. Make sure that all the injectors are working properly. You can do a pretty good job of this by using a wooden dowell from the hardware store; press one end against your ear and the other against each injector in turn. The injectors will tick when they are turned on, during each cylinder's intake stroke. If any one sounds significantly different from the others, fix that.
  • Check the FPR. Pull off the vacuum hose and make sure that you don't smell gasoline in it.
  • Use a test spark plug and make sure that each plug wire fires it.
  • Check the grounds on the ignition module and the FPR.
  • The transaxle range switch, which is operated by the gear selection lever on the console, can cause what feels like an engine miss if it is bad.
  • Check the spark plugs for appearance and fouling. HINT: I never put an old spark plug back into an engine.
  • A bad motor mount or wishbone can feel like an engine miss.

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-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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"With a scan tool, check for long-term rich or lean mixture"

i was getting a pcm code stating the above. would that cause a coil not to fire? i did have a small leak from my air filter housing into the throttle body and fixed that. my main question is: do he coils supply he initial spak to the engine/plugs or is it vice-versa ... the engine itself supplies the proper energy and data to make the coils fire? i always thought the coils fired regardless?

maybe i'm not as mechamically inclined as i thought - lol. can i get the "cars for dummies" version on what to check for? please?

still can't figure out why 2-5 and 3-8 fire, 6-7 fire as soon as tyhe car starts - then stop and 1-4 don't fire at all?

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The ICM controls when the coils fire and the PCM controls the ICM.

Ignition Control Module (ICM) - How It Works

Courtesy of Caddyshack100 (cadillacforums).

This Powertrains Ignition Control System controls fuel combustion by providing a spark to ignite the compressed air/fuel mixture in each cylinder at the correct time. This ignition control system has several advantages over a mechanical distributor ignition system.

No moving parts to wear out.

No mechanical load on the engine.

Elimination of mechanical timing adjustments.

Located for easier service and improved reliability.

Improved high engine speed performance.

The Ignition Control System consists of the following components:

Two crankshaft position sensors (A and B).

Crankshaft reluctor ring.

Camshaft position sensor.

Ignition control module.

4 separate ignition coils.

Eight spark plug wires and conduit.

Eight spark plugs.

Knock sensor.

Powertrain Control Module (PCM).

System Operation

The Ignition Control System does not use a conventional distributor or a single ignition coil. In this ignition system, both ends of each of the four ignition coils are connected to a spark plug. Each coil is connected with spark plugs on companion cylinders, i.e., on top dead center at the same time (1-4, 2-5, 6-7, and 3-8). One cylinder is on its compression stroke when the other one is on its exhaust stroke.

When the coil discharges, both plugs fire at the same time by using the engine block to complete the electrical circuit. The cylinder on the compression stroke is called the event cylinder and the one on the exhaust stroke is the waste cylinder. The two cylinders share the energy available from the ignition coil to fire both spark plugs. This method of ignition is called waste spark ignition.

Since the polarity of the ignition coil primary and secondary windings does not change, one spark plug always fires with a forward current (center electrode to ground electrode) and its companion plug fires with a reverse current (ground electrode to center electrode). This is different from a conventional distributor ignition system that fires all the plugs with the same forward current flow.

It is possible for one spark plug to fire even though a plug wire from the same coil may be disconnected from its companion spark plug. The disconnected plug wire acts as one plate of a capacitor and the engine block acts as the other plate. These two capacitor plates are charged as a spark first jumps across the gap of the connected spark plug. The plates are then discharged as the energy is dissipated as the spark continues. Voltage requirements are very high with an open spark plug or wire. The ignition coil may have enough reserve energy to fire the connected plug at idle, but possibly not under some engine load conditions. A more noticeable misfire may be evident under load; both spark plugs may then not fire.

Crankshaft Position Sensors and Reluctor Ring

The two crankshaft sensors are located on the front bank (BANK 2) of the engine block between cylinders 4 and 6. Crankshaft position A sensor is located in the upper crankcase and crankshaft position B sensor is located in the lower crankcase. Both sensors extend into the crankcase and are sealed to the engine block with O-rings. The crankshaft position sensors are not adjustable.

The magnetic crankshaft position sensors operate similar to the pickup coil in a distributor. When a piece of steel (called a reluctor) is repeatedly moved over the sensor, a voltage will be created by the sensor that appears to go On-Off-On-Off-On-Off. This On-Off signal is also similar to the signal that a set of breaker points in a distributor would generate as the distributor shaft turned and the points opened and closed.

The reluctor ring is cast onto the crankshaft between the #3 and #4 main bearing journals. The reluctor ring has 24 evenly spaced notches or air gaps and an additional 8 unevenly spaced notches for a total of 32.

As the crankshaft makes one complete revolution, both the A and B sensors will produce 32 On-Off pulses per revolution. In addition, the A sensor is positioned 27 degrees of crankshaft revolution before the B sensor. This creates a unique pattern of On-Off pulses sent to the ignition control module so that it can recognize crankshaft position.

Camshaft Sensor

The camshaft position sensor is located on the rear cylinder bank (BANK 1) in front of the exhaust camshaft. The camshaft position sensor extends into the rear cylinder head and is sealed with an O-ring. The camshaft position sensor is not adjustable.

As the rear cylinder bank exhaust camshaft turns, a steel pin on its drive sprocket passes over the magnetic camshaft position sensor. This creates an On-Off-On-Off signal sent to the ignition control module similar to the crankshaft position sensors. The camshaft position sensor produces one On-Off pulse for every one revolution of the camshaft or every two revolutions of the crankshaft. This allows the ignition control module to recognize camshaft position.

Ignition Control Module

The Ignition Control (IC) module is located on top of the rear camshaft cover. The IC module performs several functions:

It monitors the On-Off pulses produced by the two crankshaft and one camshaft position sensors.

It creates a 4X and 24X reference signal (4X REF HI and 24X Crank) sent to the PCM for ignition control.

It creates a camshaft reference signal (CAM HI) sent to the PCM for fuel injection control.

It provides a ground reference (REF LO, CAM LO) to the PCM.

It provides a means for the PCM to control spark advance (BYPASS and IGNITION CONTROL) called IGNITION CONTROL MODE.

It provides a limited means of controlling spark advance without PCM input called MODULE MODE.

The IC module is not repairable. When a module is replaced the remaining components must be transferred to the new module.

Ignition Coils

Four separate coils are mounted to the module assembly. Each coil provides the spark for two spark plugs simultaneously (wasted spark ignition). Each coil can be replaced separately.

Spark Plug Wires

The spark plug wires connect the ignition control module to the spark plugs. It incorporates several plastic channels and conduits to keep it properly positioned and to protect it. The spark plug wires are 7 mm in diameter and the outer jacket is made of silicone to withstand high temperatures. The silicone jacket is also an excellent insulator for the high voltages used in the ignition system. The silicone spark plug boots provide a tight seal on the spark plug. Care should be exercised when connecting a timing light or other equipment. Do not force anything between the boot and wiring or through the silicone jacket. Connections should be made using an appropriate adapter.

Spark Plugs

Eight spark plugs are centrally located in each cylinder combustion chamber and can be accessed through holes at the top of both cylinder bank camshaft covers. The spark plugs have platinum pads welded to the electrodes. These pads extend the spark plug life to 160,000 kilometers (100,000 miles).

Worn, cracked or dirty plugs may give satisfactory operation at idling speed, but under operating conditions they frequently fail. Faulty plugs are indicated in a number of ways: poor fuel economy, power loss, loss of speed, hesitation, shudder, medium throttle intake manifold backfire, hard starting and general poor engine performance.

Fouled plugs may be indicated by black carbon deposits. The black deposits are usually the result of slow-speed driving and short runs where sufficient engine operating temperature is seldom reached. Worn pistons, rings, faulty ignition, over-rich fuel mixture or low heat range spark plugs may result in carbon deposits.

Excessive gap wear on plugs of low mileage, usually indicates the engine is operating at high speeds or loads that are consistently greater than normal or that a plug which is too hot of a heat range is being used. Electrode wear may also be the result of plug overheating, caused by combustion gases leaking past the threads, due to insufficient torque of the spark plug. Excessively lean fuel mixture will also result in excessive electrode wear.

Broken insulators are usually the result of improper installation or carelessness when gapping the plug. Broken upper insulators usually result from a poor fitting wrench or an outside blow. The cracked insulator may not show up right away, but will as soon as oil or moisture penetrates the crack. The crack is usually just below the crimped part of shell and may not be visible.

Broken lower insulators usually result from carelessness when gapping and generally are visible. This type of break may result from the plug operating too Hot, which may happen in periods of high-speed operation or under heavy loads. When gapping a spark plug, always make the gap adjustment by bending the ground (side) electrode. Spark plugs with broken insulators should always be replaced.

Each spark plug boot covers the spark plug terminal and a portion of the plug insulator. These boots prevent flash-over which causes engine misfiring. Do not mistake corona discharge for flash-over or a shorted insulator. Corona is a steady blue light appearing around the insulator, just above the shell crimp. It is the visible evidence of high-tension field and has no effect on ignition performance. Usually it can be dust particles leaving a clear ring on the insulator just above the shell. This ring is sometimes mistakenly regarded as evidence that combustion gases have blown out between shell and insulator.

Base Ignition Timing

The base ignition timing is determined by the relationship of the crankshaft position sensors to the reluctor ring. This relationship is not adjustable and results in a base ignition timing of 10° BTDC.

IC Module Mode

There are two modes of ignition system operation: PCM mode and Ignition Control Module (IC Module) mode. In IC Module mode, the ignition system operates independently from the PCM. The ignition control module maintains a base ignition timing of 10° BTDC and is able to change this ignition timing slightly with increased engine speed. IC Module mode is in effect whenever an ignition control fault is detected while the engine is running and it will have a noticeable effect on driveability. In PCM mode, the PCM controls the ignition timing. The PCM calculates the desired ignition timing based on information it receives from the input sensors.

PCM Timing Mode

The Powertrain Control Module (PCM) controls spark advance and fuel injection for all driving conditions. The PCM monitors input signals from the following components as part of its ignition control function to determine the required ignition timing:

Ignition Control Module (IC Module).

Engine Coolant Temperature (ECT) sensor.

Manifold Absolute Pressure (MAP) sensor.

Transaxle Range (TR) switch.

Throttle Position (TP) sensor.

Vehicle Speed Sensor (VSS).

Knock Sensor (KS).

The crankshaft reluctor ring has 24 evenly spaced notches plus 8 additional notches (shaded) used for synchronization.

As the crankshaft rotates, the notches pass the position sensors and create a voltage pulse signal in the sensor that is an input for the ignition control module (ICM).

Because of the physical location of the 2 crankshaft position sensors, the signal of B lags the signal of A by 27 degrees of crankshaft revolution.

To synchronize the ignition, the ICM first counts the number of B pulses between every 2 A pulses. There can be 0, 1, or 2 B pulses between A pulses.

When the ICM sees 0 B pulses between A pulses , it starts counting B pulses between A pulses. When the ICM counts exactly 4, it synchronizes the ignition on the very next A pulse. If the ICM counts over 4 (jumps from 3 to 5), it waits for another B pulse between A pulse to start counting again.

This process allows the ignition to synchronize and fire the first spark plug within 180 degrees (1/2 engine revolution).

The camshaft position (CMP) sensor provides the ICM with cylinder #1 firing order information, which the PCM uses for sequential fuel injection.

Using 3 sensors allows the ICM to maintain ignition synchronization even if one of the 3 sensors fails.

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maybe i was a little unclear? i'm not sure which "plugs" are getting a spark, but i know the my 1-4 and 6-7 coils aren't sparking. i removed the plug wires from the coils seperately (1 coil at a time) and started the car - no arcing.

not sure if this has anything to do with it, but i'm getting codes: p300, p171, p174 and p135. i was having overheating problems prior to all of this. would the p135 be the reason? also with the car running i see a slight mist of smoke coming from under or behing the coil bank and the 1-4 coil gets very hot to the touch where as the others don't.

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"With a scan tool, check for long-term rich or lean mixture"

i was getting a pcm code stating the above. would that cause a coil not to fire? i did have a small leak from my air filter housing into the throttle body and fixed that. my main question is: do he coils supply he initial spak to the engine/plugs or is it vice-versa ... the engine itself supplies the proper energy and data to make the coils fire? i always thought the coils fired regardless?

maybe i'm not as mechamically inclined as i thought - lol. can i get the "cars for dummies" version on what to check for? please?

still can't figure out why 2-5 and 3-8 fire, 6-7 fire as soon as tyhe car starts - then stop and 1-4 don't fire at all?

I only put in the reference to the scan tool because it seemed unavoidable in the summary. Note that the paragraph continues, "Without a scan tool, you can..." and lists the causes of 99% of mixture problems. No scan tool needed for this.

Mixture problems won't cause a coil not to fire. I simply summarized the entire page of information from the FSM troubleshooting chart.

As Ranger and I said, the coils fire the cylinders in pairs, 1&4, 2&5, 6&7 and 3&8. Apparently you have issues with the coils or the ignition module, or the harness wiring between them. If you don't hear or see arching, we will assume that the plug wires are OK. Sometimes arcing in the coils isn't audible over the running engine.

P0300 Engine Misfire Detected

P0135 Heated Oxygen Sensor (HO2S) Heater Performance Bank 1 Sensor 1

P0171 Fuel Trim System Lean Bank 1

P0174 Fuel Trim System Lean Bank 2

The P0300 is obvious. The lean mixture codes tell us that you do need to check for vacuum leaks. The first thing to do is to check the air cleaner element, which can cause lean mixture codes if it is clogged. The FSM procedure for troubleshooting P0171 and P0174 says to troubleshoot other DTCs first, so, other than the easy things like checking the air cleaner element we need to fix the miss first.

The P0135 probably means that the wire on the oxygen sensor is loose. Bank 1 is the rear bank, Sensor 1 is the one one on the exhaust manifold just before the flange; it is most easily accessed from the top (!!!)(model year 1997 FSM page 6-822). The oxygen senor plug has four wires. The PNK and BLK wires are the oxygen sensor heater power and ground, and the PNK wire gets it power through fuse OXY SEN 2 (10 Amp) in the engine compartment fuse/relay center (FSM page 6-350).

The FSM procedure for P0300 checks the plugs and wires, and if there is still no spark it says to replace the coils; they don't give an ohmmeter check of the coils. As I said in an earlier post, you can check the secondary (high voltage coil) resistance of all four coils and tell if the coils for 1&4 or 6&7 are bad. If you are sure that these coils aren't arcing, you can try interchanging one of them with one of your good coils and see of the problem follows the coil; if so, replace the coil. I did a check on the Rock Auto web site and prices on a new coil vary from $17.50 to $45.89, with what looks line new OEM coils for about $43 each.

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-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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maybe i was a little unclear? i'm not sure which "plugs" are getting a spark, but i know the my 1-4 and 6-7 coils aren't sparking. i removed the plug wires from the coils seperately (1 coil at a time) and started the car - no arcing.

Have you measured the resistance of the suspicious coils as indicated in post #5? You will have to remove the coil to measure the primary resistance.
not sure if this has anything to do with it, but i'm getting codes: p300, p171, p174 and p135.
The only code that might point to ignition is P0300 and P0300 is not specific enough to be of much value.

The combination of P0171 and P0174 (both banks lean) usually indicates a vacuum leak.

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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From what you say, I would start by changing the 1&4 coil.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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im sure somewhere in my post i stated that i bought areplacement coil and it didnt produce any spark either. thought it mayhave been faulty so i took one that was sparking (2-5), put it in the (1-4 and 6-7) ... still didnt spark. also, the 1-4 coil gets extremely hot when the car has been running for a while. checked the wires to the coil assembly and they seem fine. i guess it may be the ignition module? where is that located, how much of a pain is it to replace and what is the general price range for said part?

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Diagnosis is always less expensive than arbitrarily throwing parts at a problem. The relative temperatures of your coils is a mystery to me. When you get the problem resolved, do not trash any faulty coils you identify. Consider sending them to me for analysis and comparison to others I have received. That said:

.... i guess it may be the ignition module? where is that located,

The coils bolt to the ignition module. GM calls it the Ignition Control Module(ICM).

....how much of a pain is it to replace....
You will be removing two bolts that you cannot see. Strictly by "feel". And there is a chassis ground wire that must be installed under one of the bolt heads.

While you have the ICM removed, I would install new spark plugs in the 1-3-5-7 cylinders.

....and what is the general price range for said part?
I have no idea.

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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i've been getting code "p0300" misfire. car's running like crap! i pulled the wires off the 1st coil from the left (1-4) then started the car ... coil started to arc but then stopped. 1st starts arcing when i start the car but quickly stops. i put the wires back on and did the same thing with the 2nd from the left (6-7) no arcing. the other 2 coils fire fine. i also checked for voltage with the coils off and it is getting power when the key is in the "on" position.

any suggestions - ideas?

thanks for your time.

oh yeah ... i switched the packs around to make sure it wasn't a bad coil pack and also had a new coil pack, but my 1-4 and 6-7 aren't firing.

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From Rock Auto, I saw what looked like AC/Delco OEM coils for about $43 each. They sell the module,

LX362_FULL.jpg

(other views at http://www.rockauto....fo.php?pk=49808)

for about $195 from "Standard Motor Products," who make a lot of parts for Cadillac, and $460 for the same part:

D1980A.jpg

and say that you will need gasket kit 1989579, which I found under Rock Auto's part number search for $1.16. The gaskets are apparently the little orange things you see in the Standard Motor Products part. I suspect that Standard Motor Products makes the part for GM.

Your call. I would try the plug wires first. A complete set from Rock Auto is $109:

748Q.jpg

They have another AC/Delco "kit" for $74 but no picture. I suspect that there is "some assembly required" with the kit, with something significant not included such as the spark plug boots and recommend the complete set for $35 more.

FWIW, if I was replacing one spark plug, I would replace eight. AC/Delco plugs are $41.04 for a pack of eight at Rock Auto BUT I would get them locally at the dealer or at Pep Boys because if they are dropped in shipment the gap is off, and the platinum pad may be damaged.

41-950.jpg

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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thanks for the info. my main concern is whether i actually need the part or not? the prongs on the icm are getting power to them, however, one set is reading 12.7 and the other is set/pair is reading 9.3. i'd hate to drop that kind of coin for a part that i don't need nor will be able to return.

i guess i'll have to just bite the bullet and take it to the shop (something i dread doing). i'm usually my own "mr. fix-it." i'm wondering since the pcm controls the icm if that may be the problem? cars ... i'll tell ya!!!

after looking at the pic you posted, it doesn't really seem like there is too much the icm does. just looks like a holder/bracket for the coils. as far as the wires go, i just replaced them not too long ago and it ,akes no sense buying any when the coils aren't even producing a spark. i agree plugs are a good idea - been a while since i replaced them.

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Whoa, you said that you are only seeing 9.3 Volts on one pair of ignition coils from the ICM. That should be more than enough to give you spark but since it's not 12 Volts this is a big red flag.

The schematic in the 1997 FSM on page 6-263 shows the ICM. It does several things besides operate the coils. It is what the two crankshaft position sensors and the camshaft position sensor are connected to, and can operate autonomously with a simplified emergency spark advance method if the PCM is down so that the car will still run without a PCM. It links to the PCM which provides spark advance data back to the ICM and controls the fuel injection.

The only power to the ICM is through the PNK wire on terminal C of connector C3, which gets its power from the DISTR fuse (20 Amp) in the engine compartment fuse/relay center. Connector C3 has only the power and a black ground wire on it; I would check the voltage on both. There are four connetors on the ICM, C1 for the crank sensors (YEL, PPL, BLK/WHT and BLU/WHT), C2 for the cam sensor (BRN/WHT and PNK/BLK), and C4 for the PCM (BLK, BLU/BLK, PPL/WHT, TAN/BLK, WHT, and RED/BLK) as well as C3 for the power and ground.

I don't see another schematic with the ICM and I don't see the coils on the one on page 6-263, but that's pretty simple and there are no wires: the ICM connects to each coil through two terminals on the base of each coil. With no wiring harness involved, and the ICM and coils essentially being an assembly insofar as the wiring harness is concerned, the diagram given on page 6-263 is complete for the purposes of tracing the wiring harness. But, I see nothing that would explain why you are getting 12 Volts on two or three coils but 9.2 Volts on one or two coils. Where are you measuring the 12 Volts, and where do you see the 9.2 Volts?

The circuit inside the ICM is not known to me. I do understand electronic ignition design pretty thoroughly, and I expect that one of the two terminals to each coil goes to a ground, and the other goes to a capacitor, perhaps 1 uf oil rated to 500 Volts, the other side of which is probably an IGFET and some high voltage circuitry through a set of diodes. With the coil off, you will see a pulse of amplitude 200 Volts to 500 Volts on that terminal at the spark rate. You should not see 12 Volts on these terminals.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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on the two prongs from the ICM - coil (6-7) i used a multimeter ... neg. to one prong, pos. to the other and got 12.7V. on the prongs for coil (1-4) i got 9.3V. neither of the two coil packs fire though. taking it to a friend of mines garage tomorrow ... hopefully it's nothing too major. i'll let you guys know and thanks for all the bookworming!

reggie

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The description of what to expect from the module terminals is based on the assumption that the coil driver type is capacitive discharge ignition, or CDI. A CDI with the coil connected will show no voltage except for a pulse of a few hundred volts, probably negative. If it's a solid state version of the Kettering (old points and condenser type), it will show +12 Volts across the coil most of the time, with a pulse due to the coil's primary inductance of a few hundred volts, again negative voltage, when the current is cut off. Kettering type ignitions are less efficient, particularly at high RPM, than CDI type ignitions, so just about everything out there now is CDI. But, barring specific information about the Northstar ICM, I can't say for sure.

Let's assume that it's a Kettering type. Then, most of the time the coils will have +12 Volts applied to them. If one of the coils corresponds to cylinders at TDC/BDC, a voltmeter may read just about anything from 0 Volts to 12 Volts across the terminals. One way to find out is to spin the crank and check again.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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