96 Seville STS 4.6 Northstar

[randu2020]

The fans don't kick on at any temperature. I have to turn on the A/C or the heater to get the fans going. The fans will stay running at high speeds while the A/C is on but when the heater is on the fan speed changes from slow to fast at intervals. I assume the relay in the fuse box is working because the fans are coming on with the heat and A/C so does this sound like a wiring problem? I am going to check the coolant temperature sensor now but I believe it is good. If so what else can be done to troubleshoot the situation?

[Cadillac Jim]

The fans should run on low speed when the A/C is on and the engine is cold. The temperature at which the engine must be to turn the fans on high speed is independent of the A/C. If the fans are on high and turning off the A/C turns off the fans, there is something weird about the wiring.

The PCM controls the fan relays. Make sure that the wires to the fan relays go to the PCM, or at least disappear into the wiring harness, to be sure that someone hasn't modified the fan wiring.

[BodybyFisher]

With the AC on, the fans run continuously

With the AC off, the fans come on at about 226 and go off at 217

With the AC on, you will see a narrower fluctuation of temps on your gage.

It sounds like your fans are running correct, just keep the AC off, let the temp rise and see if they are on.. at about 226, it might take some local stop and go to get there

[randu2020]

I let the engine run until it gets close to the red and the fans will not kick on. I have an uncle who is a mr. goodwrench mechanic in texas but he wants to know what the computer is saying the temperature is besides looking at the gauge. He wants to see if maybe the gauge is wrong or different from what the IPC shows. The problem is that I can't see my temperature with my INFO button. It only cycles a few other tools nothing to do with temperature. Is there a way to make that temperature show up digitally with my info buttons? I tried using the diagnostic manual to mess around with the settings but I can't find any way to access that information. Is it even possible or is he mistaken? Thank you for all the help you guys are great. I just bought this thing three days ago and believe the car salesman knew something was up so he just wanted to sell it for a low price and move on so I'm new to this cadillac thing. Thanks again for your help.

[BodybyFisher]

Do me a favor and check for DTC codes, go to www.caddyinfo.com, go to HOW TO, go to DTC Codes, follow the directions for your year and post the codes here and check them at this site

http://myweb.accessu...90/dtcobd2.html

There are cooling fan codes that can be set, I doubt this is your coolant temp sensor.

I trust you have check all cooling fan fuses, relays for corrosion, etc

[Cadillac Jim]

There is a way to include the temperature with the other data using the INFO button. You change an IPC override data value for IPS05. You have an STS, thus the analog dashboard with the speedometer and tachometer needles, so the factory setting is to skip the coolant temp.

IMPORTANT WARNING

You can brick the DIM (IPC computer module) by blowing this operation. This happens when you change an override data value but fail to store it properly for any reason. This sets the DTC B1557 (EEPROM Calibration Error) which cannot be reset. The IPC must be exchanged by a dealer, who will use your old IPC to get your instrument calibration data that was set at the factory for all the instruments in your car to set up the new IPC module.

The process for changing the overrides, including the warning, are on page 8C1-21 of the 1997 FSM.

HOW TO AVOID BRICKING YOUR IPC

When you are working with any of the override codes, they will be displayed as the trip odometer value. After you change any override code, permanently store the new value by simultaneously pressing and holding the <Front Defrost> and <A/C> buttons for about five seconds, until the trip odometer flashes once, then release them.

You can check that the new override value has been stored by pressing OFF button; if the IPC displays the IPC CLEAR CODES message then the new override value didn't store properly, turn the key off and wait 15 seconds to make sure that you exit the diagnostic mode properly without changing anything, then start over.

To change an override value, with the key on (engine on or off), enter the diagnostic mode by pressing and holding the OFF and <PASS WARMER> buttons simultaneously and holding for several seconds; all the dash lights and display segments will come on except the MIL; this is the check that all the lights and segments work (the MIL is on when the key first is turned on but goes off; that's its check). The FAN Up/Down rocker is the YES/NO switch; press NO to skip reading all the codes out on the dashboard. You will get a message "PCM?" and you select NO, then you get the message "IPC?" and you select YES. Select NO for IPC DATA and IPC INPUT, then, for IPC OVERRIDE, select YES. You are now in the bricking-the-IPC-if-you-are-not-verrry-careful mode.

Select NO until you get to IPS05, which is called "Option E (driver message center display options)" in the 1997 FSM. This should bring up the number 43 in the trip odometer (it may be something else if someone has changed it). You need to ad 64 to that number; if it was 43 that means that you need to increment it to read 107. You do this by using the PASS Up (warmer) to increment it, PASS Down (cooler) to decrement it. When you get it to read 107 you are done, press the <front defrost> and <A/C> buttons simultaneously and hold for about five seconds until the trip odometer display blinks once. Then, press the OFF button; if you drop out of the diagnostic mode you are done but if it displays the IPC CLEAR CODES message then turn the key off (SEE WARNING ABOVE). If in doubt at any time, turn the key off, wait 15 seconds, and start over.

You can also ask a dealer to do this. They won't brick the IPC, or, if they do, it's on them to fix it.

[randu2020]

Do me a favor and check for DTC codes, go to www.caddyinfo.com, go to HOW TO, go to DTC Codes, follow the directions for your year and post the codes here and check them at this site

http://myweb.accessu...90/dtcobd2.html

There are cooling fan codes that can be set, I doubt this is your coolant temp sensor.

I trust you have check all cooling fan fuses, relays for corrosion, etc

I have checked all the fuses and relays. Everything looks fine in that department. I ran the codes this morning and only received a PC0603 (PCM Keep- Alive Memory reset), a TC0073 (PCM-TCS interface fault), a PZ1971 (inadvertent Power malfunction), a IR1740 (IRC configuration error), and a RF2560 (RFA message validation error) This is quoted directly from the diagnostic manual for my car error code pages.

I also checked the wiring and it all looks normal. When I bought the car a few days ago it would run hot faster than it does after I installed the missing thermostat, very slight water penetration on the back side of the water pump so I replaced that because it was cheap. So far the only thing I haven't checked is the coolant temperature sensor. I flushed the block and the radiator and replaced with new anti-freeze. This makes the car run a little cooler compared to what it was but this did not solve the problem. I checked the purge line and it was fine. Last thing I want to do is a block test because there is no water in the oil, no leaks of any kind from the car itself, and it runs like a brand new car, idles perfect, and good fuel consumption so I wouldn't see it being a headgasket unless I am mistaken. I will try what Jim says then I will see what happens. I really want to keep the car because it looks and runs like new except for the heating and fan problem. Thanks again folks and I will post again soon.

[randu2020]

There is a way to include the temperature with the other data using the INFO button. You change an IPC override data value for IPS05. You have an STS, thus the analog dashboard with the speedometer and tachometer needles, so the factory setting is to skip the coolant temp.

IMPORTANT WARNING

You can brick the DIM (IPC computer module) by blowing this operation. This happens when you change an override data value but fail to store it properly for any reason. This sets the DTC B1557 (EEPROM Calibration Error) which cannot be reset. The IPC must be exchanged by a dealer, who will use your old IPC to get your instrument calibration data that was set at the factory for all the instruments in your car to set up the new IPC module.

The process for changing the overrides, including the warning, are on page 8C1-21 of the 1997 FSM.

HOW TO AVOID BRICKING YOUR IPC

When you are working with any of the override codes, they will be displayed as the trip odometer value. After you change any override code, permanently store the new value by simultaneously pressing and holding the <Front Defrost> and <A/C> buttons for about five seconds, until the trip odometer flashes once, then release them.

You can check that the new override value has been stored by pressing OFF button; if the IPC displays the IPC CLEAR CODES message then the new override value didn't store properly, turn the key off and wait 15 seconds to make sure that you exit the diagnostic mode properly without changing anything, then start over.

To change an override value, with the key on (engine on or off), enter the diagnostic mode by pressing and holding the OFF and <PASS WARMER> buttons simultaneously and holding for several seconds; all the dash lights and display segments will come on except the MIL; this is the check that all the lights and segments work (the MIL is on when the key first is turned on but goes off; that's its check). The FAN Up/Down rocker is the YES/NO switch; press NO to skip reading all the codes out on the dashboard. You will get a message "PCM?" and you select NO, then you get the message "IPC?" and you select YES. Select NO for IPC DATA and IPC INPUT, then, for IPC OVERRIDE, select YES. You are now in the bricking-the-IPC-if-you-are-not-verrry-careful mode.

Select NO until you get to IPS05, which is called "Option E (driver message center display options)" in the 1997 FSM. This should bring up the number 43 in the trip odometer (it may be something else if someone has changed it). You need to ad 64 to that number; if it was 43 that means that you need to increment it to read 107. You do this by using the PASS Up (warmer) to increment it, PASS Down (cooler) to decrement it. When you get it to read 107 you are done, press the <front defrost> and <A/C> buttons simultaneously and hold for about five seconds until the trip odometer display blinks once. Then, press the OFF button; if you drop out of the diagnostic mode you are done but if it displays the IPC CLEAR CODES message then turn the key off (SEE WARNING ABOVE). If in doubt at any time, turn the key off, wait 15 seconds, and start over.

You can also ask a dealer to do this. They won't brick the IPC, or, if they do, it's on them to fix it.

I did what you said and now I have the temp on my DIC, thanks a lot. It helped me to monitor my temp better and my fans also started kicking on at 222 and not allowing it to run hot like it was doing. I burped it last night for about 20 minutes so I don't know if that had anything to do with it as well. I heard that an air bubble could keep your sensor from working right and not allowing your sensor to trip the relay. However, just the info for the temp control was great and helped a lot so thank you. One last question, what are normal operating temps for my 1996 northstar 4.6? I heard it was from 215-225, does that sound close? If so then the problem must be solved for now since it will not get past 225.

[Cadillac Jim]

215 F to 225 F is a good range to keep in mind for most normal driving, including city driving in hot weather. I don't think that the engine should ever get hot enough for the fans to go on high speed while the car is moving more than 25 mph on a continuing basis, no matter what the outside temperature is or whether the A/C is on or not.

[randu2020]

215 F to 225 F is a good range to keep in mind for most normal driving, including city driving in hot weather. I don't think that the engine should ever get hot enough for the fans to go on high speed while the car is moving more than 25 mph on a continuing basis, no matter what the outside temperature is or whether the A/C is on or not.

Sweet, thank you for the information. This web site rocks and I will continue to share what I can with you guys. So far so good with the car since I signed up for this web site. Any new people reading this post needs to know that within a few hours of me signing up here my caddy started running like normal again. CaddyInfo rocks, thank you guys.

[Ranger]

205-215 was normal for my '97 Deville (digidash). Can't tell the actual numbers on this one.

[randu2020]

215 F to 225 F is a good range to keep in mind for most normal driving, including city driving in hot weather. I don't think that the engine should ever get hot enough for the fans to go on high speed while the car is moving more than 25 mph on a continuing basis, no matter what the outside temperature is or whether the A/C is on or not.

Since this web site helped to cure my car faster than the mechanic I know is there anything you can tell me about self charging the AC on my 96 seville STS northstar 4.6 that you could tell me?

[BodybyFisher]

Do me a favor and check for DTC codes, go to www.caddyinfo.com, go to HOW TO, go to DTC Codes, follow the directions for your year and post the codes here and check them at this site

http://myweb.accessu...90/dtcobd2.html

There are cooling fan codes that can be set, I doubt this is your coolant temp sensor.

I trust you have check all cooling fan fuses, relays for corrosion, etc

I have checked all the fuses and relays. Everything looks fine in that department. I ran the codes this morning and only received a PC0603 (PCM Keep- Alive Memory reset), a TC0073 (PCM-TCS interface fault), a PZ1971 (inadvertent Power malfunction), a IR1740 (IRC configuration error), and a RF2560 (RFA message validation error) This is quoted directly from the diagnostic manual for my car error code pages.

I also checked the wiring and it all looks normal. When I bought the car a few days ago it would run hot faster than it does after I installed the missing thermostat, very slight water penetration on the back side of the water pump so I replaced that because it was cheap. So far the only thing I haven't checked is the coolant temperature sensor. I flushed the block and the radiator and replaced with new anti-freeze. This makes the car run a little cooler compared to what it was but this did not solve the problem. I checked the purge line and it was fine. Last thing I want to do is a block test because there is no water in the oil, no leaks of any kind from the car itself, and it runs like a brand new car, idles perfect, and good fuel consumption so I wouldn't see it being a headgasket unless I am mistaken. I will try what Jim says then I will see what happens. I really want to keep the car because it looks and runs like new except for the heating and fan problem. Thanks again folks and I will post again soon.

You can have a breached head gasket and not get oil in the water, lets get the fans working first. So you are saying that the temp gage goes up to almost RED and the fans don't come on with the AC off, correct?

[randu2020]

Do me a favor and check for DTC codes, go to www.caddyinfo.com, go to HOW TO, go to DTC Codes, follow the directions for your year and post the codes here and check them at this site

http://myweb.accessu...90/dtcobd2.html

There are cooling fan codes that can be set, I doubt this is your coolant temp sensor.

I trust you have check all cooling fan fuses, relays for corrosion, etc

I have checked all the fuses and relays. Everything looks fine in that department. I ran the codes this morning and only received a PC0603 (PCM Keep- Alive Memory reset), a TC0073 (PCM-TCS interface fault), a PZ1971 (inadvertent Power malfunction), a IR1740 (IRC configuration error), and a RF2560 (RFA message validation error) This is quoted directly from the diagnostic manual for my car error code pages.

I also checked the wiring and it all looks normal. When I bought the car a few days ago it would run hot faster than it does after I installed the missing thermostat, very slight water penetration on the back side of the water pump so I replaced that because it was cheap. So far the only thing I haven't checked is the coolant temperature sensor. I flushed the block and the radiator and replaced with new anti-freeze. This makes the car run a little cooler compared to what it was but this did not solve the problem. I checked the purge line and it was fine. Last thing I want to do is a block test because there is no water in the oil, no leaks of any kind from the car itself, and it runs like a brand new car, idles perfect, and good fuel consumption so I wouldn't see it being a headgasket unless I am mistaken. I will try what Jim says then I will see what happens. I really want to keep the car because it looks and runs like new except for the heating and fan problem. Thanks again folks and I will post again soon.

You can have a breached head gasket and not get oil in the water, lets get the fans working first. So you are saying that the temp gage goes up to almost RED and the fans don't come on with the AC off, correct?

I got that fixed as of this morning sometime. When I changed my IPC code to give me the digital temperature read out the fans started kicking on as they are supposed to and it hasnt ran past 222 all day today. Thanks again. Just trying to figure out the safest way to charge my ac now, any ideas?

[KHE]

Just trying to figure out the safest way to charge my ac now, any ideas?

Is the system totally empty of refrigerant? If so, it must be evacuated with a vacuum pump for 45 minutes and then the refrigerant needs to be charged into the system. It will take three cans of plain R-134a. Do not use any refrigerant that contains "seal conditioners" or sealants.

[scott y]

A couple ozs. of PAG in there before you start to evac. won't hurt either...

[KHE]

A couple ozs. of PAG in there before you start to evac. won't hurt either...

Not necessarily. The only time oil should be added to the system is if there was a major leak or one of the components was replaced. Too much oil will reduce cooling performance.

A few years ago, I repaired a Chevy Astro van's A/C that wouldn't cool properly - I drained 20 ozs of oil from the system... The owner added oil every time he added refrigerant...

[randu2020]

Just trying to figure out the safest way to charge my ac now, any ideas?

Is the system totally empty of refrigerant? If so, it must be evacuated with a vacuum pump for 45 minutes and then the refrigerant needs to be charged into the system. It will take three cans of plain R-134a. Do not use any refrigerant that contains "seal conditioners" or sealants.

It still works as of now it is just not as cold as it can so I thought I would go ahead and charge the unit while I am in this get it done mood lol.

[KHE]

Just trying to figure out the safest way to charge my ac now, any ideas?

Is the system totally empty of refrigerant? If so, it must be evacuated with a vacuum pump for 45 minutes and then the refrigerant needs to be charged into the system. It will take three cans of plain R-134a. Do not use any refrigerant that contains "seal conditioners" or sealants.

It still works as of now it is just not as cold as it can so I thought I would go ahead and charge the unit while I am in this get it done mood lol.

If it is not as cold as it should be and you haven't received the REFRIGERANT LOW warning on the DIC, then it probably just needs one can or R-134a.

[scott y]

A couple ozs. of PAG in there before you start to evac. won't hurt either...

Not necessarily. The only time oil should be added to the system is if there was a major leak or one of the components was replaced. Too much oil will reduce cooling performance.

A few years ago, I repaired a Chevy Astro van's A/C that wouldn't cool properly - I drained 20 ozs of oil from the system... The owner added oil every time he added refrigerant...

[scott y]

A couple ozs. of PAG in there before you start to evac. won't hurt either...

Not necessarily. The only time oil should be added to the system is if there was a major leak or one of the components was replaced. Too much oil will reduce cooling performance.

A few years ago, I repaired a Chevy Astro van's A/C that wouldn't cool properly - I drained 20 ozs of oil from the system... The owner added oil every time he added refrigerant...

IT's too bad that one couldn't determine the amount of oil in the system before a "top up" is performed,since a small rerigerant leak also means a small oil leak...

[scott y]

I don't believe in the old "It probably just needs to be recharged" thing...they don't consume refrigerant, they leak it and must be repaired. Here in Canada we cannot "top up" knowing full well that there is a leak.

[KHE]

All automotive refrigerant systems will leak a trace amount of refrigerant over time. Wether it be at the shaft seal on the compressor or some of the o-rings at the line connections. The leak will be so slight, an electronic leak detector won't even pick them up but over the course of 14 years, it adds up.

If the system leaked down enough refrigerant where a loss of performance was noticed in a few weeks or a few days, then there is a substantial leak that needs to be repaired.