Electrical Problems

[Phillip]

I am getting desperate. I have been battling a parasitic drain on my battery for over a year. If anyone has "Shelock Holmes" tendencies and knows the electrical system of a 96 Caddy, I have a challenge for you.

This car seems to be posessed. Last year I had a parasitic drain that was draining my battery in a couple of days (about 0.6 amps). The diagnosis pointed to a PZM which I replaced to no avail. I thought I had the better of it when I put a kill switch in line with the Radio/Phone fuse. This seemed to do the trick for the winter. This spring, it started draining again. The kill switch had no effect on the 0.26 amp drain. Now, months later, after checking and rechecking every fuse and relay, I still can't figure out the source of the problem.

This is an extremely condensed version of what is going on. I have left out the days spent reading the electrical sections of the factory shop manual. Any suggestions are welcome.

Thanks,

Phillip

[JimD]

....This spring, it started draining again. The kill switch had no effect on the 0.26 amp drain. Now, months later, after checking and rechecking every fuse and relay, I still can't figure out the source of the problem.

That is a very large power-off current draw value. The "normal/expected" current draw is in the range of .035 to .05 amperes. And even that much current draw will render a battery useless after two to four weeks (depending on the age/condition of the battery).

All I can suggest is place your ammeter in the loop and start pulling fuses to see if you can identify the offending module/system.

[Phillip]

Yes, I would be thrilled to see the draw go down to the prescribed 0.03 amps. I have been using an ammeter to measure it and perform the diagnostics so far, but no luck yet. All I can tell is that if I pull the Comfort fuse, the problem goes away. It used to work with the Radio/Phone fuse, but that all changed for no apparent reason. The PZM seems to be the common factor but the response is the same with both of my PZMs so unless the same thing is wrong with both of them, I am thinking it must be outside of that module.

Thanks for the suggestion.

[Cadillac Jim]

Modules themselves usually aren't the problem. If you hook up jumper cables with reverse polarity, use a 24 Volt fast charger with the battery connected, or some other such, yes, you can damage electronics. But, electronics themselves are generally very reliable.

I'm sure by now you have run the OBD II codes and have determined that there is no help there.

Actually you have told us quite a bit here. For example, 0.6 amps on the RADIO/PHONE fuse is about 7 Watts, which is quite a bit -- about the same as a typical household night light. And, 0.26 Amps on the COMFORT fuse is still about 3 Watts, enough to light up an accessory.

I think that you have two problems, one on each of the RADIO/PHONE fuse and the COMFORT fuse. My 1997 FSM, page 8A-11-1, shows both fuses. Since the COMFORT fuse is the one in play today, we'll start there. The FSM says that the circuit fed by the COMFORT fuse is on page 8A-11-25. On that page, there are five things fed by that circuit, all with ORN wires:

1. The PZM, through pin 83 on connector C1.
2. The Heater and A/C Programmer at pin C3 of connector C1.
3. The Controlled Power Relay in the Trunk Compartment Relay Center (#3) at pin C5.
4. The Remote Function Actuator (RFA) module at pin A.
5. The Compact Disc (C/D) Changer at pin 5.

Since the Retained Accessory Power is controlled here, something there could be drawing your 3 Watts. Interestingly enough, pages 8A-15-0 and 8A-15-11 show that the RADIO/PHONE fuse is on the Controlled Power Relay.

The direct line to the PZM is not the problem. This is the "keep alive" power to the PZM and is very, very little current.

I don't know anything about the heater and A/C programmer. I think that this is the set of buttons on the HVAC panel that control the fans, heater, and A/C. If there is a dash light on in it that shouldn't be on, you should be able to see it through the windows in a dark garage. A problem here is a real long shot.

We'll go through the Controlled Power Relay separately below.

The Remote Function actuator (RFA) module is a computer on the network that performs the actions you command through your key fob, and possibly by OnStar. It's just a couple of computer chips on the car's network and this very likely isn't your problem, either.

If you have the trunk-mounted C/D changer, it is on this line. This is a real, live possibility. A CD can stick in it and cause it to try endlessly to eject the CD, causing this drain. You can probably hear it if you open the trunk and lean down. If so, open the door to the changer and remove the CD cartridge as quickly as you can without forcing it; it will then eject the CD, in its holder or separately, and you can put them back into the cartridge and put everything back together. If that doesn't do it, or you can't get the cartridge out of the changer easily, pull the plug on the back of the changer and come back here. I've been there. Some guy tried to play his CDs on my car stereo when I was having it serviced or something and I found and fixed everything for free, not counting the cost of my FSM set. Also, a really bad pothole while the CD player is working can cause this. I can help.

Now we are at the Retained Accessory Power. The FSM page 8A-1-25 revers us to page 8A-15-0 for this circuit. This circuit feeds four fuses in the Trunk Compartment Fuse Block:

• AMP FUSE, 30 Amps
• CLUSTER FUSE, 20 Amps
• PZM FUSE, 10 Amps
• RADIO/PHONE FUSE, 10 Amps.

We'll begin with the RADIO/PHONE fuse because it looks like it might be both problems.

A relay is controlled here. Both front power windows switches and the radio are on one circuit, which is the ACCESSORY TIME DELAY RELAY. If you can park the car, turn off the key with the radio on, and the radio goes off when you open the driver's door, this relay is switching off that circuit. Page 8A-15-1 refers us back to page 8A-11-0 for each of the four fuses.

We'll start with the RADIO/PHONE fuse as before, looking at circuits other than the ACCESSORY TIME DELAY RELAY. The FSM says that these circuits are on page 8A-11-32. On that page, lots of stuff is on this line. The Radio Interface Module (the part behind the dash, not the "real" radio in the trunk high on the rear seat to the left), the cell phone (if you have one, or if you have OnStar), and the High/Low Beam Head-Lamp Relay in the engine compartment micro relay center. And, we have the fuel door release relay and, if you don't have option B90 -- whatever that is -- the trunk release relay. The only thing that looks like 3 Watts to me here is a relay coil. Check for a sticking or dirty switch on the dashboard for releasing the fuel door or the trunk. If you haven't had any problems closing the fuel door or the trunk lid, and the buttons and fob work OK, these aren't likely a problem. The only thing that looks like 7 Watts is the cell phone, which looks exactly like 7 Watts. You may not have had any problems with it since the cell phone companies cut service for analog phones, but likely it's not squarely on the hook in the console compartment. That's got to be your 7 Watts. The radio could be your 3 Watts but let's complete the search over the circuits before we go there because that's not likely either.

The AMP fuse provides power to your radio amplifiers. To some degree this depends on which radio you have, and there is an astonishing variety of radios available. The simplest thing I can tell you to do is to pull the AMP fuse and see if your 3 Watts is going there.

The CLUSTER FUSE provides power to the steering wheel air bag, the steering wheel controls (the little triggers, two each to the left and right), and the Instrument Panel Cluster. If your instrument panel is dark and the steering wheel controls aren't lit at night, that isn't it. There is a remote possibility that somthing in the IPC is a problem; pulling the CLUSTER fuse will tell.

We are left with the PZM fuse, which page 8A-11-0 says is on page 8A-11-27, and provides switched power to the PZM pin B11 of connector C1. It's possible that something powered by the PZM is the power drain. The PZM is treated in section 8A-51, and some diagrams that show a lot of stuff on one page is available there. In particular, the PZM fuse that leads to the PZM module pin B11 of connector C1 is the "low power driver output" line of the PZM. That would be things driven by the PZM that don't draw a lot of power, like the Valet switch and the Rear Compartment Lid Tamper Switch.

SUMMARY

Note that when you pull a fuse and look at current draw, you mist wait until the inadvertent power cuts off. That can take 20 minutes. Disturbing the car can turn it back on and reset the timeout clock to zero. If you can work on the car without usng the key or opening the doors, you may be able to keep the power drain at minimum so you can tell what is going on.

The low-hanging fruit is that your phone was off the hook until the 0.6 Amp drain went away, and your valet switch in the glove box is set ON, or that your trunk lid was forced recently and the Compartment Lid Tamper Switch is closed, in which case your security system should be making this known to you.

It's possible that other things are on the low power outputs of the PZM too. Pulling the fuse marked PZM (10 Amp) in the Trunk Compartment Fuse Block between the AMP (30 Amp) and RADIO/PHONE (10 Amp) fuses will tell the tale there.

I would start with that fuse. Then, in order, pull these fuses:

1. CLUSTER FUSE (20 Amp)
2. AMP FUSE (30 Amp)
3. RADIO/PHONE (10 Amp)

If that doesn't get it, or if you've already been everywhere discussed here, come back and let's go from there.

[adallak]

Have you got that 260 mA after you left everything alone for some 15-20 minutes? For some 10-20 minutes the car may draw up to 0.5A, then that value should drop to some 20-30 mA. My security system was drawing additional 100 mA, so I had to pull the fuse every time I left the car for night. I know how frustrating this type of problems may be. Just my $0.20.

[Phillip]

Thank you guys for the tips. As adallak suggests, I could remove the fuse, and have done this before by wiring a kill switch in series with the offending circuit, but that no longer works so I am back at it.

I would especially like to thank Jims-97-etc. I printed off the document you sent and went back out to work through your suggestions. This was very well prepared and certainly helpful. Woefully, at the end of the night I have still not found the problem, but I took some notes and they follow. They are largely statements describing the affect of the proposed diagnostic interventions.

1. There are two DTC's: RS0038 and P0300. RS0038 is suspicious, but I have removed the fuse from that circuit without any success. The misfire is new and my scan tool actually showed a cylinder 4 misfire. Seems like something unrelated and I will get to this when I solve the electrical problem.

2. From the shop manual, I had already concluded that the problem was most likely in the circuits associated with the COMFORT fuse so I have already tried disconnecting A/C Controller, Remote Function Actuator and CD Player. None of these had any affect. Also, the Controlled power relay had no affect, but more on that later.

3. The Accessory Time Delay relay works as it should. Further, I have unplugged and it has no affect.

4. My car does not have a cell phone or OnStar.

5. I connected the Ammeter, sat inside the car (I have the interior out of it so simplify access) and waited for the PZM to go to sleep. Following is the sequence if followed: (noteL the times are approximate)

- current varies for about 60 seconds

- current drops to 2.45 amps for 60 seconds

- current drops to 0.68 amps for 8 minutes

- current increases to 2.4 amps for 60 seconds

- current drops to 0.3 amps and stays there.

Total length of time is just over 10 minutes. I waited a further 15 minutes to be sure it was finished.

6. Removed the AMP fuse - no affect

7. Removed the CLUSTER fuse - no affect, but it woke up the PZM upon reinsertion, going back to 2.4 amps but only the last two steps of th above cycle so that it dropped to 0.3 amps after only 60 seconds.

8. Removed the RADIO/PHONE fuse - same as the CLUSTER fuse.

It was getting late by this time so I had to pack it in, but I did make a few more observations.

- the CONTROLLED POWER RELAY was warm and stayed warm the whole time. Removing it had no affect and I replaced it with one from another car and that had no affect.

- I decided to start checking the circuits as described in the various diagnostic procedures, even though I did not get any trouble codes. I only got one done before I called it quits for the night. I checked that PZM connector C1 terminal C11 was not faulting to ground as per PZ1972.

I think the next step will be to continue checking differnt circuits, but without a code, I am not too confident. I am also quite interested in the warm relay. I will give this some thought as well.

As always, suggestions are welcome and will be followed up on and thanks for putting up with my rambling. Finally, I am really impressed with anyone who has the patience to read this whole thread.

[Cadillac Jim]

P0300 Engine Misfire Detected

S038 Electronic Level Control Exhaust Valve Short to Ground/Open

The RS0038 is apparently and OBD I code; the 1996 model year did carry some of those over. The R probably means that it was thrown by the RSS funciton checks. I think that this is the equivalent OBD II code:

C0662 Level Control Exhaust Valve Circuit Low

This could mean that the connector is off of the ELC valve, a wire is broken in the line to the ELC valve connector, or the solenoid itself is bad. It probably isn't a leak, and it may not be serious unless i'ts CURRENT or comes back quicly all the time, or the rear of the car rides high or low. It probably isn't your battery drain problem.

As you have already noted, the P0300 means you have a miss and that can be dealt with when you are done with the parasitic drain.

I wouldn't give up on using the FSM and its daigrams and contnuing to pull fuses just yet. Pulling the fuse tests the circuit for power drain definitively and convincingly at essentially zero risk and in the quickest time possible for such a test.

I noted that you did NOT pull the PZM fuse in the trunk compartment fuse block. This provides power for all the PZM functions that aren't driven by relays, and is the most promising circuit, since you've eliminated the cell phone and the CD player.

The fact that the Retained Power Relay stayed warm, and that removing and replacing the CLUSTER and RADIO/PHONE fuses had any effect (i.e. waking up the PZM when they were put back) says that the Controlled Power Relay was on. This means that your battery drain could not be expected to be at minimum yet. If pulling that relay solves your power drain, then you aren't waiting long enough.

Park the car with all the doors closed to wait. Using the key in a door lock will wake up the PZM. I'm not sure but I think raising the trunk lid will wake up the PZM. I know for a fact that opening a door will wake up the PZM because if I left my GPS plugged in the cigar lightter, it will come on if I use the fob or open the car door.

[Phillip]

I agree with your statement about the codes. Not too likely that is the problem.

I think you are on to something with respect to the control power relay being on. If it is warm it is on. That is pretty much a guarantee. Interstingly enough, I tried to jumper the relay (ie. removed it and jumpered the terminals to the OFF position) and this didn't prevent the parasitic load. I will try it again and wait longer. I have generally been waiting about 15 minutes but perhaps I should wait longer just to be sure.

With respect to the fuses, I was assuming that the PZM went to sleep when the drain dropped to .3 amps, but perhaps that is not the case. I have tried pulling each fuse out to no avail, but I did this after the drain dropped, based on the assumption the PZM was asleep. Maybe I need to wait longer each time. That will be a very slow process.

The one fuse that did shut things down was the COMFORT fuse, which feeds the PZM through terminal C1 B3. When that fuse is removed, the load immediately drops to 0.02 amps. I have considered putting a kill switch on that fuse, but it is rather disruptive.

I will give it more thougth and see what I can come up with tomorrow. I will focus on the Controled Power Relay I think.

Thanks again.

[Phillip]

I took Friday night off, but am back at it today. I am taking a more aggressive approach now. I have a second meter and am monitoring multiple points.

Today I focused on the Retained Accessory Power circuit. I removed the Controlled Power Relay and put an Ohm meter from terminal B7 to ground, while also monitoring the current. The expectation being that after 10-15 minutes, the PZM would remove the ground from B7. This did not happen, which explains by the controlled power relay was staying warm. I also checked terminal A1 of the Accessory Time Delay Relay, which should be grounded for 10-15minutes before the PZM removed the ground. Again, the ground remained indefinately.

Further, with the CPR removed, there was 12 v potential at terminal C7. If I am not mistaken, this terminal is supposed to be fed by the CPR from either the Controlled Power Backup Relay or the Body 3 fuse. I removed the CPBR but this did not affect the voltage at C7. I did not remove Body 3 fuse, but I did find that removing the PZM fuse removed the potential at C7.

My brain is full for now. I will think about this and then go back at it. Any thoughts are, as always, welcome.

Thanks.

[Cadillac Jim]

The backup relay turns on the controlled power relay when the car is cold and the key is turned on. I looked for the amount of time that the PZM takes to turn off the controlled power but didn't find it last night. I don't have time right now but will be back later to look at your details and work over the schematic with your information.

I do recall someone saying that it takes up to 40 minutes to remove power from the controlled power relay. I'm almost positive that it's more than 15 minutes.

One simple way to tell is to put something on the cigar lighter, like a cell phone charger or cradle, a GPS cradle, or whatever, so you can see when the power is on without touching the car. When I get back I'll look and see if the map lights and such are on with that relay.

[Phillip]

According to the shop manual, the PZM should remove the ground from the Controlled Power Relay (CPR) and Retained Accessory Power Relay (RAPR) after 10 minutes or when a door is opened. This does no happen.

What is really puzzling me, is the way the RAP circuit feeds the AMP, CLUSTER, PZM and RADIO/PHONE fuses. From the schematic, it looks like they are fed from the CPR from terminal C7. This also appears to be the source for the control circuit of the RAP , through the RADIO/PHONE fuse. If that is the case, then the PZM does not need to remove the ground from the RAPR since the control circuit will be de-energized by the switching of the CPR. I suspect I must be missing something important here.

[winterset]

what kind of radio do you have?

do you have an OEM amp in the trunk? if you have a CD player, or source button, or DSP, you should. that is on a separate fuse in the trunk called "AMP" that might be staying on.

[Phillip]

Thanks for weighing in. I have the factory Bose stereo with a 12 disc CD changer in the trunk. I have disconnected the CD changer since they are somewhat notorious. I have also tried removing the AMP fuse to no avail. I am still suspicious of the radio but I am focusing on the Retained Accessory Power cirucuit right now.

[Cadillac Jim]

Your drain is low enough at 0.26 Amps or 3 Watts to just be relays at this point.

We never did hear if puling the PZM Fuse (10 Amp) from the trunk compartment fuse block, the one between the AMP and RADIO/PHONE fuses, did the trick.

Phillip, you are right, I finally found the timeline for the PZM on page 8A-15-3 of may 1997 FSM. The paragraph on shutting down the car, "Disabling," reads:

When the ignition switch is cycled "OFF," the body control module (PZM) keeps the controlled power relay and accessory time delay relay energized and starts a ten minute timer. After ten minutes, the PZM removes ground from CKT 707 (BLK) and CKT 755 (BLK) de-energizing the controlled power and accessory time delay relays, cutting off battery voltage to the accessory circuits.

The PZM also monitors the position of the doors. If a door is opened, the corresponding door jamb switch closes, grounding the PZM door jamb input terminal. The PZM then removes ground from CKT 707 (BLK) and CKT 755 (BLK), de-energizing the controlled power and accessory time delay relays regardless of the elapsed time.

This basically says that the system shuts off either on a 10-minute timeout or when a door opens.

The Enabling section just says that the PZM wakes up when the key is turned on. The Enabling and Disabling functions are summarized in a paragraph CIRCUIT OPERATION that precedes the details in the Enabling and Disabling paragraphs.

I know for a fact that this isn't all that wakes up the PZM because the unlock function of my key fob wakes up the PZM, as does turning a key in the driver's door. The RFA (key fob) also wakes up the PZM because it must do so to open the trunk or operate the door locks, turn on the headlights and courtesy lights, etc.

This gets us to a possibility that really isn't in the FSM on that page: a shorted or intermittent switch that keeps waking up the PZM. This could be a switch associated with turning the key in either front door, any door switch or another switch that involves the PZM, like the Rear Compartment Lid Tamper Switch.

On a long shot, make sure that the valet switch in the glove compartment is not on. Other things on the Body Control Module section schematics (8A-51 in my 1997 FSM) include a trunk ajar input, door lock inputs, LH and RH lock cylinder inputs, the valet lockout input, and the trunk tamper input. Each of these can be tested at the PZM connector. If you have a PCM you can get the wire colors and connector pinouts.

[Phillip]

Thanks again for the input. I really need someone to bounce ideas off of. I have already tried the valet switch with no success. I have been studying the drawings and making notes for the past two days. Tomorrow I am going to unplug the PZM and check the function of each of the circuits connected to it. This will probably take a while. I still don't know what to make of the data bus. I guess I will leave that alone for now. I am hopeful that this exercise will find the circuit that is keeping the PZM awake. If it is another one of the modules, that will have to be another day.

I will keep you posted on my progress.

[Phillip]

I spent another evening stuck in the car trying to diagnose the problem.

I started by checking all the input circuits to the PZM, thinking that maybe a door switch or something like that was keeping the PZM awake. They all tested OK.

I checked the function of the Controlled Power Relay and Accessory Time Delay Relay. This time, the ATDR functioned correctly but again, the CPR remained energized. The PZM never removed the ground from the CPR. This is puzzling since the PZM controled the ATDR which should operate based upon the same inputs as the CPR. Since I have another PZM, I tried this with both and they both did the same thing. The circuit to the CPR seem to be OK. I found no evidence of a short to ground or a broken wire.

All these tests took a few hours and I ran out of time and energy. I will not be able to try more tests tomorrow but should get another chance on Thursday, but I seem to be spinning my wheels. I just can't seem to wrap my mind around what is going on. I can only afford to give this a little more time and then I will have to resort to a "kill switch" on the Comfort Fuse. Actually, before I do that I may look at other locations for the "kill switch" so it will be less disruptive to the overall operation of the car.

Anyway, that is the latest in my saga. Thanks for your patience.

[Cadillac Jim]

Look for a short in the ground line of the CPR by unplugging the PZM and seeing if the CPR remains activated.

[Phillip]

I checked the wire from the PZM to the CPR and it was fine (ie. no short to ground). In fact, removing the Comfort Fuse is the only way to remove the ground from the CPR unless you remove the PZM. Based on this, I am confident the PZM is able to ground and remove the ground from the CPR. Also, since the PZM is controlling the Accessory Time Delay Relay (ATDR), it seems that the PZM is getting the appropriate signal to control the CPR. It sure seems like a bad PZM, but it is hard to believe two PZMs would behave the same. I should check a few more things here.

If I don't find it here, I think I will have to give up since the shop manual does not have enough information to go much further. Do you think a Tech II would be much use here? I really don't like the idea of spending $80/hour for a mechanic to do this very slow diagnostic work, but if it was quite fast with a Tech II, maybe it would be worth it.

Hmmm.....

[Logan]

No, the GM Tech2 is nice. But it is not a fast way to figure out odd problems. It's a nice tool to have. But it is not a fast 'fixall'.

[Cadillac Jim]

I agree with Logan, a Tech II will likely tell the tech pretty much wat you know: something is keeping the PZM awake, but it probably won't tell what is keeping the PZM awake.

Whatever *is* keeping the PZM awake is likely on a fuze. Have you pulled the PZM Fuse (10 Amp) from the trunk compartment fuse block, the one between the AMP and RADIO/PHONE fuses? The 0.36 Amps could just be relay coils but I think that a relay should draw less than that.

[Phillip]

Yes, I have pulled all the fuses, including the ones under the hood. The only one that has had an impact is the Comfort Fuse. I checked my notes because I seem to recall that one of the engine compartment fuses also shut it down, but I can't find the note describing it. I will check again. Just some food for thought, when I remove the CPR, the load drops by about 0.14 amps. I checked the resistance on the coil of the CPR and it was 85 ohms, right on the nose. Therefore, two relays stuck on would give give the drain that I am experiencing. With the CPR, I have identified one, but I haven't found the other yet. Further, I haven't found why the PZM won't switch the CPR off.

My next step is going to be to see if I can find the other relay that is sticking on, assuming it is a relay. If not, then I have to start searching for some other source of resistance.

[Cadillac Jim]

I think that your 0.26 amps amounts to two relays. Something is irritating your PZM. Disconnnect these until you find your culprit.

A time-saver is to find all that you believe might be the culprit, and disconnect all of them. If the PZM goes to sleep, you know that your perpetrator is in the list of suspects. Then, connect half of them. I'll leave it to your imagination how to complete the identification of the guilty signal in one or two more 10-minutes cycles.

[Phillip]

Well I made some progress today. I found that, with the AMP fuse removed, the PZM would go to sleep and the drain would drop to 0.02 after 20 minutes. There is still some strange behavior with the Retained Accessory Power system. While it seems to operate correctly (the radio shuts off when you open the door) the Controlled Power Relay and the Accessory Time Delay Relay remain grounded by the PZM. After 20 minutes without being disturbed, the PZM finally removes the ground from the ATDR but still not the CPR.

My next step is to study the manual some more. I want to see what is on the AMP fuse that will keep the PZM from going to sleep.

Any thoughts are always welcome and appreciated.

Thanks.

Phillip

[BodybyFisher]

I have been following this with great interest, good patience you have.

Have you swapped out the CPR, maybe the contacts are fused closed? Maybe the PZM is removing the ground but the relay is staying engaged?

[Texas Jim]

I too have been following this.

I am very interested in the outcome.

It is like a good mystery story with the detective trying to catch the bad guy...but JUST BARELY MISSING HIM...every chapter.

Maybe a poor analogy...but it is all I can think of at the moment.

I can hardly wait for the ending.