Trios

Hello folks. I've been trying to diagnose a parasitic drain on my 2003 Coupe. I followed the instructions in post #590 in Bill Curlee's troubleshooting thread (Cliff's: disconnect battery, hook DC ammeter up in series, check amps pulled from battery after 10-15 minutes; start pulling fuses to find culprit circuit). I found that I was sitting at 250 milliamps draw after 15 minutes (actually, after 3 hours, but I got distracted). This is far more than the expected 40ma.

So, in my fuse-pulling and circuit-testing extravaganza, I noticed some things: relay 37 (listed as "MONITORED LD") was quite warm to the touch. I pulled this relay and watched as my meter went from .25 to .15 amps; a significant load. However, pulling fuse 2 ("MONITORED LD"), which powers the equipment that this relay powers (which seems to be such things as the map/vanity lights, things that the system would turn off if you forgot and left them on), makes no difference in the amp draw. So I don't think it's something that this relay is powering but the relay itself that's drawing 100ma; I replaced the relay with the one labeled "TONN REL" (41) which I figured, since I don't have a convertible, is probably brand new/never used. The load dropped to .22 amps; still too much, but an improvement.

The only other fuse that made more than a negligible difference in my current draw was 25, listed as "BCM1 & IPC", which literally dropped the current draw to 0.01 amps fluctuating off the scale to 0.00. This also caused relay 37 to shut off.

So, where do I go from here? The BCM seems to be pulling a lot of current, with 70-100ma just from that relay. Is that relay supposed to be powered all the time/warm to the touch?

Any help greatly appreciated.

Bill Curlee

Well,,,,,,,,,,,,,,,,,,,,,,, You cant pull EVERY FUSE cause the BCM is what makes the car go in to sleep/security mode.

The Monitored relay circuit SHOULD time out in 10-12 min.

Have you checked the seat motors

BC

Trios

Ha! Sorry about that, I suppose I wasn't terribly clear. I was pulling a single fuse, and then letting the car go back to 'sleep' to check the amp draw. Then I would replace that fuse, pull a different one, and then check again.

So that relay should turn off...it doesn't seem to be. I pulled the fuse labeled, SCM-L, but it didn't make a significant change. Why isn't there a SCM-R? Also, is there a better way tho check the seat motors than fuse pulling?

Bill Curlee

Because the passengers seat is a manual control seat and it doesnt have a control module..

dadaroo

If you can get the sleep mode current draw in the range of 20ma that is as good as it gets from my knowledge base.

Quicksilver Vert 01

Relay #37 should not be powered all the time. That relay should be turned off when the BCM enters the sleep mode.

Has the BCM ever gotten wet from A/C condensate in the passenger footwell? I would take a close look at it.

Trios

That just makes too much sense. Thanks Bill; should I just try and reach under the seats and disconnect any connectors I find then?

Yeah, but my car is drawing 250 milliamps, not 20.

I verified after waiting an hour from my last post last night, I checked the current draw and it was still 250ma, and then I opened the door and quickly reached in and felt that the relay was still warm, so it is definitely not shutting off.

I do not *believe* that the BCM has ever gotten wet. I was in the footwell (quite literally, upside down, face inches from the fuse block/bcm) and there was definitely no water there now, and that was after a 2 hour drive that morning with the a/c on. Other than saying I saw/felt no water yesterday and saw no signs of prior water, I still can't rule it out 100% since I don't *always* have my face in the footwell.

Is there a sequence of events that has to happen for the BCM to decide to sleep? Where should I look next?

Bill Curlee

There are several things that are connected directly to the HOT AT ALL TIMES (B+) buss that pulling fuses will not effect. Disconnect these and see if it causes the current draw to drop:

Alternator B+ (BATT Terminal ) on the back of the alternator.

Head Light Control Module

Seat Control Module

Here are some things that have been well known to remain on and cause excessive current draw:

Rear Window Defogger
BOSE AMP
Seat Lumbar Motor
Seat position motors
IGNITION SWITCH contacts remaining closed after the switch was turned off.

You can NOT remove BCM fuses because it controls the security / sleep mode and is a major part of the 20 milliamp draw.

BC

Trios

Bill,

When I pulled fuse 25, "BCM1 & IPC" and the battery drain dropped to 0.01 fluctuating to 0.00, so essentially off the scale of my ammeter and 10 or less milliamps, doesn't that rule out any and all of the above and prove that it is either the BCM itself or something the BCM controls that is causing my 250ma draw?

I guess I would like a specific answer to this question: what situation can cause relay 37 to stay active at all times?

dadaroo

The relay could be failed internally so that the contacts are closed. You can pull it and do a check with an ohmmeter. If you don't know how to do this, email me with your phone number. You probably want to put in a new one since it had been hot for so long, they are cheap.

Quicksilver Vert 01

That's not very likely, since the OP mentioned that the relay is quite warm to the touch.

Warmth is an indication that the relay coil is being energized, causing the normally open relay contacts to become closed.

dadaroo

I agree with Quicksilver, I should have had my coffee first.

Quicksilver Vert 01

I'm the same way!

Trios

I still haven't had my coffee yet today and I'm hopped up on codeine cough syrup, but I agree with Quicksilver as well. I even swapped the questionable relay with the one labeled 'TONN REL' which I believe to be the tonneau release relay for a vert. I don't have a vert, so this relay should be brand new. At first, swapping the relays brought the current draw down some 30 ma, but after that relay warmed up it seems to be exactly the same as the one that I swapped out.

I will pull out my FSM here in a bit to see if I can find some info on the BCM not shutting down all the way since I seem to have stumped the forum.

Quicksilver Vert 01

Relay #37 has a constant +12 volt power source on the positive side of it's coil. It becomes energized when the BCM, through it's internal logic, completes the ground circuit to the negative side coil connection on the relay.

It's possible that BCM has a shorted output, which causes a constant ground path to relay #37, and keeps it energized constantly, regardless of the programmed BCM logic parameters.

Trios

I agree this is a possibility, but I am more of the opinion that the BCM is not going into sleep mode. I am leaning that direction due to the still rather high amp draw after I pull the relay (150ma), and the extremely low amp draw when I pull power to the BCM.

I've been staring at schematics for the past 20 minutes or more and I'm starting to go cross-eyed.

From the FSM:
Relevant circuits:













Now, what I cannot figure out is where the BCM monitors that 'ground' to turn on or off the MONITORED LD relay. None of my schematics seem to be showing that input to the BCM.

Additional relevant data from the FSM:

So, my other option seems to be to find each of these inputs to the BCM and disconnect them one-by-one until I am able to determine which one is the culprit.

Quicksilver Vert 01

That's easy enough to determine by watching either your interior courtesy lamps, or the under hood lamp.

Open your hood or a door, while the key is in the off position. The interior or under hood lighting should turn off after 15 minutes, indicating the BCM sleep mode has started.

Closing and then reopening a door or the hood again, will initiate another 15 minute BCM awake period, and the observed lighting will be on again.

Trios

Well, that is sort of the point. Relay 37 is the relay that actually controls the courtesy and underhood lamps; if that relay is on, those circuits have power (first schematic above). So, since relay 37 is staying on, those circuits do in fact have power. I haven't checked it the way you specified (I will later today, by plugging the underhood lamp back in and leaving the hood up) but I strongly suspect that after 20 minutes the light will still be on...

Quicksilver Vert 01

I have the same strong suspicion as you.

dadaroo

If I am correct, relay 42, the BCM, and relay 37 are interrelated. If you pull relay 42, relay 37 should become de-energized. That might seem to indicate the BCM is not the culprit since it may be functioning correctly based on the state of relay 42????

I am just learning to read the C5 schematics, let me know if I am incorrect.