Parasitic Drain Woes

[notch8]

Givens: '96 base eldo, 79k miles, Bose UTO/UQ4/U1S option w/12 disc cd changer in trunk. Intermittent problems with the trunk pulldown (wouldn't pulldown) , now both front speakers have terrible static (noise) in them.

I got 44 mos. out of a new 108 mo. battery, eventually got NO BATTERY CHARGE on the DIC, so I started investigating.

Battery was shot, got a new 9year Everstart Maxx , had the alternator rebuilt and tested, replaced the $20. trunk pulldown switch (lower, black switch) and noticed when I hooked up the ground wire to the new battery, I had a HEALTHY spark.

2-3 amps when first connected-5 mins. drops to 1.5 amps- 10-15 mins. drops to 250 mA. Got out the FSM and started checking- pull Comfort fuse, drain is gone. As per FSM, disconnecting the RFA Module, the CD changer and the ACM (heater & ac programmer) had no effect. Unplug the PZM-the drain is gone. Also, unplugging the Controlled Power Relay has no effect but I did notice that the relay was WARM! Unusual-?

I know the battery and alternator problems were due to the constant draining and recharging going on for 3 years, without me even knowing it. The car was being driven everyday. Lately, it's been sitting so the problem surfaced.

I can't get the drain to go below 250mA (.25 on the 10AMP scale). The PZM or the CPR circuits are at fault. According to the FSM, the PZM should, after 10 mins., remove the ground from the CPR, which I believe it does but what about the relay(CPR) being warm? The PZM controls just about EVERYTHING- I really don't know where to start. Any thoughts from the pros out there are greatly appreciated!

Roger

PS The last drain test was done with the following unplugged- radio, rear view mirror, pwr. antenna, cd changer, trunk pulldown motor, trunk and underhood lights- reading was 250mA. Also, ever since I've owned the car, almost 4 years, whenever you open the trunk, I get a faint whiff battery acid smell. I thought it was from the trunk pulldown motor area-maybe it's from behind the rear seat.

[MAC]

Unplug the PZM-the drain is gone. Also, unplugging the Controlled Power Relay has no effect but I did notice that the relay was WARM! Unusual-?

I know the battery and alternator problems were due to the constant draining and recharging going on for 3 years, without me even knowing it. The car was being driven everyday. Lately, it's been sitting so the problem surfaced.

Well, it sounds like you found the answer since by disconnecting the PCM (Powertrain Control Module) the drain stops. PCMs can go bad. I've replaced mine and I know a few other members here on Caddiyinfo have replaced theirs. Unless you're able to diagnose the specific problem in the PCM and have the knowledge to replace whatever is defective, you will have to buy a new or remanufactured one.

Have you check for trouble codes?

[Cadillac Jim]

I think he unplugged the PZM, not the PCM, to isolate the power drain that far.

Is your ammeter a mechanical one (meter with swinging needle) or a digital one? The reason that this is important is that mechanical ammeters often aren't linear, and they may not be accurate at the lower end of the scale. If you have, or can borrow, a digital multimeter and measure the current with a digital meter, you can get an accurate measurement. Since digital meters are pretty much the norm these days, I'll assume that you have an accurate measurement and go forward.

Since you didn't mention OBD II codes, I'm assuming that you ran them and there wasn't anything interesting. In any case, like MAC says, please post them here just in case.

I don't think that a warm relay means anything, unless it's warm when it's supposed to have been off for a long time.

The normal quiescent power drain is 50 ma, so we are after the last 200 ma. This is 6 Watts, about what a small bulb would draw. Candidates for this draw are the map lights, the glove compartment light, a visor mirror light, and the trunk and underhood lights that you disconnected. Start by making sure that the headlight switch knob isn't rotated all the way to the detent, turning on the courtesy lights. If there is anything running off of battery power, such as a cell phone charger, GPS, or radar detector, unplug that. One way to find this kind of thing is to look over your car in a very dark garage without touching the fob or the car.

If you've done all that, then let's see what others have to say that have solved this problem. I haven't had it myself but I do have a 1997 FSM and will provide another pair of eyes on the schematics.

[notch8]

Hey Jim

Yes, I'm talking about the PZM, (Body Control Module), in the electronics bay behind the rear seat.

Yes, I'm using a DVM. The last time I ran the car, 3-4 days ago, I got:

0603-H

1520-H

PZ2473-something to do with the hi-beams, am not having trouble with them-so I don't know?

I also have a '97 FSM, it's the closest my tight-a$$ could afford-LOL LOL! It says 30mA max. on parasitic drain.

No cell phones or gps, nothing plugged into lighter, no interior lights on, I've checked after dark and felt lights for heat.

Today, I pulled the PZM out, removed the case, examined and it looks brandnew, no hot spots, nothing.

I know looks mean nothing, just reporting.

I've been studying the schematics-lots and lots of info-I appreciate another set of eyes!!!

The FSM says to replace the PZM as a last resort and I agree-I'm not there yet.

After every PZM action, you have to wait 20 minutes for the PZM to go back asleep to measure, during that period, I think the RAP relay (engine compartment fuse panel) clicks as does another relay in the #2 relay center(controlled power back-up relay) I think- anyway there's a LOT going on. This is all with the key OFF!!!

I'm going to try to check the main CPR (controlled power relay) for correct operation and go from there.

I've been fooling with this for about a week- it's frustrating. Anyway, thanks for the reply, I'll keep you posted.

Roger

[Cadillac Jim]

P0603 Control Module Long Term Memory Reset

P1520 Transmission Range Switch Circuit

B2473 High Beam Fault

The P0603 means that the battery has been disconnected lately. The P1520 means that the PRND21 switch needs adjusting. The B2473 means that you have a high beam headlight bulb out, or there's dirt in the socket or a loose connector.

It's normal for activity to continue in your car with the key off for up to 15 minutes. That's why the battery drain takes a few minutes to drop down to 30 ma.

A sticking relay could do it. You have retained power for awhile for the cigarette lighter and a few other things. It times out to save the battery when you leave the cell phone charger plugged in or whatever. It comes back on when you hit the key fob or open a door. You can check it by turning on a dome light and seeing if it turns off in about 40 minutes.

I'll post to this thread later today after I've had time to study the FSM.

[Dave in Texas]

I always love a good electrical mystery. I'm retired now but spent 40+ years as an Electrician. I'm interested in the outcome of this problem. A question: new Bat/new Alt.....new Bat cables too? 12yr old OEM cables can cause many nasty fault-problems. Shiney-clean/tight connections are always a good thing with Batteries/Cables. I went through something similar with my older DeVille, but my problem with more with not driving the car enough. Bought and now use a Battery Tender Plus to keep my garage-queen at full-charge power. Hang in and remember the KISS principle.

[Cadillac Jim]

At this point I think I've duplicated a lot of your work with the FSM. Pages in the 1997 FSM of interest:

• Page 6-212, Traditional Excessive Current Draw.
• Page 6-552, DTC P1520, Gear Indicator System. The first thing it says under Diagnostic Aids is to check the adjustment of the switch.
• Page 8A-10-9, Power Distribution, Body 3 Fuse, showing the Comfort Fuse.
• Page 8A-11-1, showing the Comfort Fuse in the trunk compartment fuse block and identifying that zone schematic as page 8A-11-25
• Page 8A-11-25 showing the loads on the Comfort Fuse.
• Page 8A-15-0 and -1, showing the Retained Accessory Power circuits. I think this is where the problem is; see below.
• Page 8A-51-0 and -1, showing everything on the PZM.

The first think I would do is pull the Controlled Power Relay and see if the load is on it. If it is, look on pages 8A-15-0 and -1 for all the things on the relay. Don't disregard the possibility that the relay coil itself may be the drain. I believe that you said that it was warm, and if the car has been off for a hour or more it should be cold. Note that there is a Controlled Power back-up relay; pull it and check the load with both relays pulled if you see the load with the main relay pulled. If it's still there with both relays pulled, then we are off to the PZM page, 8A-51-0. But, note that the PZM fuse is on the Controlled Power Bus (see the distribution in the dotted box at the top of page 8a-51-1) so I don't think that the PZM gets power after the 40-minute retained power delay if these relays both cut off. You can pull the AMP, Cluster, and Radio/Phone fuses. If pulling the Radio/Phone fuse stops the drain, I would pull the Accessory Time Delay relay and see if that does it. If so, use a voltmeter to see if its terminal A1 is grounded after the 40-minute delay is over; if it is, then we are looking at the PZM itself. If not, the PZM is operating that relay correctly and the problem might be solved by changing the time delay relay.

On the PZM page, 8A-51-0, I see some simple things to check. Make sure that your valet switch in the glove compartment is off; the drain just may be something to do with the valet mode. If the Trunk button on the dash opens the trunk lid, you aren't in the Valet mode. Pull the horn relay in the engine compartment; it's a long shot but it's there. Also, pull the rear defogger relay, again a long shot.

I think the problem is somewhere in the circuits shown on page 8A-15-0 and -1. As best I can tell, the way the controlled power works is that the ignition switch turns on the controlled power back-up relay which puts power to the PZM fuse shown on page 8A-15-1, turning on the PZM, which then grounds the coil of the Controlled Power Relay. As long as that relay is on, you will see some power drain just from the relay coil and the PZM power, and I think that could be your 200 ma. The thing that keeps this relay on after the key is shut off is the PZM but I think this relay is sticking or possibly shorted.

One last possibility: the radio. You said that the front speakers have a lot of static. If you have the Bose system, the front door speakers are active, which means that they have the amplifiers integrated with the speakers. If both of them are noisy, either the noise is coming from the radio, but the rear speakers aren't noisy, so we may have a bad connection or partial short in the radio circuit. Look on page 8A-11-32 for the circuits on that fuse. If the Radio/Phone fuse stops the battery drain, then you have eliminated most of the other circuits on this fuse, so unplug the radio and see if that's it.

[notch8]

Pulled both power relays-600mA drain

With both relays pulled out-amp/cluster/radio-phone/pzm fuses stay hot-I don't understand how?

Pulled 50a body 3 fuse-20mA drain

Pulled amp/cluster/radio/phone/pzm fuses-580mA drain

New codes: 0603h/1552h/1911h/1552h/1558-BIG PROBLEM/1971-NOT SURPRISED/2471/2473/IR2225-can't find in FSM. (I know all the codes but the last one)

1558EEPROM ERROR first time for this-don't understand fsm explanation-will pzm clear codes or do I? Can I clear codes using DIC?

Looking like bad PZM and bad Inadvertant Relay-not sure yet.

Left reading light on and pzm turned it off-good.

Timed delayed power also works-open a door and radio dies.

Jim-sorry if post seems short-I typed alonger more detailed one and accidently deleted it before I got it posted-sorry.

Too much info too quick. Will try to digest your last post later. Thanks for your help-I'm sure we're on the same page.

Roger

Also, think pzm controlled ground circuit 775 to hi pwr relay(CPR) may be constant indicating a bad pzm? Explains warm relay? Still can't understand hot fuses with both pwr relays pulled!

[notch8]

Cleared codes as per FSM instructions using DIC-neat, first time for that! Currently -no codes.

Drain involves Body 1-2-3 fuses.

With Body 3 pulled, PZM makes a squealing noise until a door is opened or the fuse is replaced. I think it made the noise with only the Comfort fuse pulled also. Not sure what that means, if anything? PZM doesn't like having it's power taken away-don't know.

I'll keep posting-

Roger

[rek]

A long shot...Take out the door jam switches and unplug them. Check again for the squealing noise.

Take apart the switches. Look for corrosion that might form a bridge between + and --.

[notch8]

Was ready to replace PZM but currently have 0.00 to 0.010mA drain. 0.030mA is allowable. Maybe pulling and reinserting relays made a difference. I'll keep monitoring. Thanks for all the help.

Roger

[JimD]

Was ready to replace PZM but currently have 0.00 to 0.010mA drain. 0.030mA is allowable. Maybe pulling and reinserting relays made a difference. I'll keep monitoring. Thanks for all the help.

Roger

I expect pulling relays (and fuses and connectors) would certainly scrub any corrosion/oxidation from blade contacts and that scrubbing could cause a non-functioning circuit to start operating normally.

But how that scrubbing action would put a stop to a parasitic drain is beyond my experience. It's hard to argue with your results, however.

Keep us informed of your findings and I, for one, would appreciate your thoughts as to the "why" your efforts were successful.

[notch8]

Not sure about the 'WHY'. I never replaced anything. I made 3 separate tests today with everything connected, both doors shut and waited 30 minutes each time. Each test resulted in 0.00-0.010mA draw. Before, I was testing with the pass. door open and waiting 20 min. between tests.

Also, these tests were made after clearing all the codes out of the PZM-difference-I don't know.

I know my car doesn't conform to my '97 FSM RAP (Retained Accesory Power) schematic.

Is there a difference between '96 and '97-again I don't know.

I'm 55 and have worked on cars and motorcycles for 40 years-I know they don't heal themselves.

Roger

[JimD]

....I know my car doesn't conform to my '97 FSM RAP (Retained Accesory Power) schematic.

Is there a difference between '96 and '97-again I don't know.

GM/Detroit Three make "improvements" continuously. Service Manuals could easily fall behind the (accuracy) power curve for XXX months, or more.

As an example, the federal mandated (EPA) switch-over to OBDII code standards was effective for vehicles produced after 12/31/1995. That mandate left the (unanswered) question of "what about 1996 model year vehicles produced before 1/1/1996?"

So, yes; there could easily be a difference between '96 and '97 model year specifications in the published Service Manuals.

After all that discourse, I would be pleased with your measured current. In fact, I would be content with any figure less than 100ma!!

Thanks for the feedback.

[Cadillac Jim]

If you were keeping the passenger door open, you were likely keeping the PZM alive. A relay coil and the PZM could easily be the 200 ma you were looking for.

[notch8]

Jim-I agree about the door.

Final thought-

Apparently I do not have a parasitic drain! I ran the test again today and paid close attention to the time.

At 20 minutes into the test I had 240mA drain, at 25-30 minutes I had 0.00-0.010 mA drain. The FSM says

to check after 20 minutes, I guess my PZM takes a little longer to shut down or something is keeping it

awake a little longer than normal.

A HARD lesson learned!

Roger

[JimD]

Write this one down, folks! The 20 minute RAP timer is an approximation.

Good job, Roger.

[Cadillac Jim]

As best I could tell from the schematic the time delay was in the PZM itself. When it cut off the ground from the switched power relay, that cut off the power to the PZM.

I find it a little surprising that the times would vary between cars. The simplest time delay within the PZM would be a counter, but it's possible that it is an analog timer of some kind like the 555 IC; in CMOS form it can be almost zero power and is very reliable and can switch the relay ground, while a counter will clock the microprocessor and draw current. However, microprocessor current should be a whole lot smaller than the relay coil current. A counter would set the time delay with a crystal clock, which means that all cars would have the same delay within microseconds. An analog timer will have something like 10% or 20% variation between cars, or a couple of minutes either way of 20 minutes. Also, a counter in the PZM would be software and thus zero incremental cost for that function, while the timer would require at least one tantalum capacitor, which would cost a few cents per car. Hey, maybe the microprocessor clock is an internal ceramic oscillator, which will have a percent or two variation between cars?

However, I'm not in the car electronics design business. That world is closed by proprietary interests and competitive information protection, and by a lot of existing technology that would be very expensive to replace. In addition, some parts of the technology is at least partly locked in by international automotive standards such as 12 V negative ground with a nominal running voltage of 14 Volts. With the general rule "if it ain't broke, don't fix it" a lot of things stay as they are until something comes along to mess with it.

One of my pet rocks is the 42 Volt standard that has been under consideration by the auto industry for a decade. Arcing and safety problems are daunting, and may have killed it. I suggested a 42-Volt, 400 Hz three-phase with neutral system some years ago but it was a non-starter, because it would have required development of high-volume, low-cost technology that didn't exist and thus would have added cost to the implementation. The fact that this solves the perennial ground problem for lighting, triac switching, neutral current safety cutoff like GFP outlets and breakers in household circuitry, and existing low-cost 400 Hz motors, bulbs and other stuff from the aircraft industry, and obvious cost and efficiency savings in most systems aren't interesting because the closed community would have to develop all that stuff for off-the-shelf automotive use while cagily exchanging information between manufacturers.