I thought this would be an easy one, as I have read through numerous posts on this topic. Still can't figure this out.

Symptoms:

I have no error codes up and everything is functioning normally in the car.

473mA draw after 10mins.

What I've found (all measurements taken from -ve battery lead):

Removing the cable going to the inside fuse box results in 2mA of current draw (therefore all current draw is coming from the inside fuse box)

#25 (BCM1 & IPC) 328mA draw

Unplugging the BCM (this is the box beside the fuse box, right?) and plugging in fuse #25 results in 407mA, therefore the BCM was taking 66mA.

#18 (hvac) = 1mA
#4 (scm) = 9mA
#3(lumbar) = 1mA
#5(rdo/cd) = 26mA
#6(pk t/lp) = 4mA
#27(hvaccon)= 11mA
#25(bcm1&ipc) = 328mA
#29(c/laldl)= 17mA
#30(dcm-r)=30mA
#33(dcm-l)=30mA
#16(sdm)=1mA

All other fuses made no difference in current.

If you add up all the draws, they come to: 458mA. Total draw is 473mA. Therefore if the other draws were turned off, there would be 15mA of draw.

Unplugging all of the relays from the inside fuse box makes no difference.

Unplugging the field connector for the alternator makes no difference.


My conclusion is this:

There are a ton of loads that are adding up to my total current draw, well above the 25mA it should be. Since there are so many different current draws (the larger ones being control modules), it is not the individual control modules that are the problem.

The BCM is not shutting down the other loads (dcm, etc). Unplugging the BCM only resulted in a reduction of 66mA, so the BCM itself is not shorted and is not taking a lot of current. However, when testing the cuircuits without the BCM connected, there is no communications taking place with the other modules and therefore the other modules don't shut down. So, without the BCM in place, you would expect a higher current draw due to the other modules not being shut down. That is why removing my BCM and testing current did not solve my problem, even though I removed what I thought was the faulty component.

My only other question is this: Something else on the BCM/IPC circuit is taking 262mA. Will the IPC take this kind of current if the BCM is not shutting it down?

Does this conclusion make sense? Anyone with any other ideas? I don't want to spend the money on a new BCM if it won't solve the problem.

 

Check your driver side seat switch. We have put in a lot of these for shorts in C5's. Good luck

 

Pulling the seat fuses did not result in a reduction in current, so I think that rules the seat switch out????

 

Anyone?

 

Make sure the big three grounds are upgraded?

 

Hi, the last thread that I read about a large current draw and pulling fuse 25 alleviating it, had his dash light switch on very dim. He went through everything in the car and had dozens of suggestions, when he finally happened upon the dash dimmer switch being on. Others have found the rear view Mirror lights on, and the vanity mirror lights not shutting off, you have to look very close in a dark environment.
Good Luck

 

By some chance, do you have a 6 or 12 CD changer? Same symptom was found in another C5, and the current draw was caused by leaving the CD changer door in the open position. When closed, the current draw stopped. Hope you're as fortunate!

 

Nope, no CD changer.

I'll look at the lights, but I checked the dash already and it's off. There are 4 circuits in my car that are taking over the 25mA that I should be seeing TOTAL. That is what is confusing.

That should mean that it is not any ONE thing. For example, if it was the IPC, and I fixed it, 3 other circuits would still be putting me well over 25mA.

I'm not sure how the grounds factor in. Poor ground and the electronic modules don't work right and continue to take power?

If you look:
#25(bcm1&ipc) = 328mA
#29(c/laldl)= 17mA
#30(dcm-r)=30mA
#33(dcm-l)=30mA
#5(rdo/cd) = 26mA

Yes, something on the bcm circuit is taking most of the power, but both dcm loads are high, as well as the laldl and rdo/radio. I think that means that the dcm's are not shutting down. Which, I think, means one of two things: Either the bcm is faulty and not shutting them down, or something is happening in the car (driver still in the car) that makes the bcm think that it shouldn't be shutting down the loads.

What I am looking for is if anyone has ever encountered a situation where multiple loads are over the 25mA sleep state? If anyone has seen this, what was the problem?

Anyone with a bad device in the car (driver's seat, IPC, etc), wasn't only fuse responsible for that device over in current? Or, did one bad component cause multiple fuses to be over 25mA??? A bad device shouldn't be sucking extra current from fuses it isn't even connected to.

 

Hi the BCM won't go to sleep if something is keeping it awake, therefore it will not shut down the other draws even if there is only one item continuing to run even intermittently when it should't be. So by practice if a bad seat switch were there and drawing current the BCM would stay in alert mode, The same can be said for any of the other items that will draw power. I've heard of the passive unlock system causing a power draw because the fob is constantly activating the door locks even from in the house of the owner, and the car being in the driveway, garage or on the street. I've also heard of those who put an ipod/mp3 player adapter in the system and even though the device is not plugged in, the adapter still drawing power, thereby keeping the BCM awake. If the ipc was on, the BCM would stay awake and so would the other items that go to sleep with the BCM.
Good Luck

 

Solved my current draw by replacing the computer..all other tests failed to show any problem. Battery would go dead in only a few days with the car just sitting in the garage. It was an expensive long shot but it worked..Vette can now sit for several weeks and start right up.

 

Are you using a digital voltmeter and where are you measuring at?

 

Digital ammeter, measuring current on the -ve battery lead (ammeter in series with battery -ve terminal and -ve battery cable).

This was the info I was looking for. If one bad device can keep the bcm from stutting down, then it appears I can see the symptoms I am seeing with a failure other than the BCM.

If the above is true, I should be able to pull all the fuses (removing power to all of the devices that the BCM monitors) and then add one fuse (device) at a time. The BCM should shut down that device and and go to sleep within 10 mins, since the faulty device should not exist. If I put in the fuse for the faulty device, I should see the BCM not go into sleep mode. So I would slowly add one fuse at a time and make sure the bcm sleeps after 10 mins. Any fuse that stops it from going to sleep after 10mins is the bad device! If the BCM doesn't sleep with all fuses removed but #25, then it has to be the BCM or the IPC.

Does this sound right?

 

ps, wouldn't you HEAR the door locks constantly activating?

 

Hi, yes that is the way to go about trying to find the draw. The BCM fuse has to stay in, and you pull every other one 1 at a time and guage the result. As for the door locks, you would hear them if you were next to the car when they were activating. But it's intermittent, and you may have to sleep next to it all night. I read about some posters that had the keys on their dresser, in the bedroom, and the doorlocks were activating off and on all night on the car in the garage. This is only with the passive fobs, their solution was to turn off the passive switch, and some got new fobs that weren't passive.
BELOW is an explanation of the BCM Awake/Sleep modes...
Good Luck
++++++++++++++++++++++++++++++++++++++
Body Control System Description and Operation
This vehicle is equipped with a Body Control Module (BCM) capable of performing multiple body control functions. The BCM, which is the power mode master, is responsible for sending the power mode messages on the serial data line to other systems.

Serial Data Power Mode
On vehicles that have several control modules connected by serial data circuits, one module is the power mode master (PMM). On this vehicle the PMM is the Body Control Module (BCM). The PMM receives two signals/circuits from the ignition switch. These are the Ignition 1 and Ignition 2 ignition switch signals/circuits.

To determine the correct power mode the PMM uses:

The state of these signals/circuits, either switch closed (B+ = 1) or switch open (B+ = 0)
The sequence of switch closures received by the PMM
The status of the engine run flag
The chart below indicates the modes detected and transmitted by the PMM:

Correct Ignition Switch Inputs Power Mode Selected/Expected
Engine Run Flag Serial Data
Sampled Ignition Signal State
Power Mode State
Key-In Sense

Ignition 1
Ignition 2

OFF
0
0
0
OFF-AWAKE
NA

RAP
0
0
1-0
RAP
NA

UNLOCK
0
0
0-1
UNLOCK
NA

ACCESSORY
0
0
1
ACCESSORY
NA

RUN
1
1
1
RUN
NA

RUN
0
1
1
RUN
NA

CRANK
0
1
1-0
CRANK
NA


Fail-safe Operation
Since the operation of the vehicle systems depends on the power mode, there is a fail-safe plan in place should the PMM fail to send a power mode message. The fail-safe plan covers those modules using exclusively serial data control of power mode as well as those modules with discrete ignition signal inputs.

Serial Data Messages
The modules that depend exclusively on serial data messages for power modes stay in the state dictated by the last valid PMM message until they can check for the engine run flag status on the serial data circuits. If the PMM fails, the modules monitor the serial data circuit for the engine run flag serial data. If the engine run flag serial data is True, indicating that the engine is running, the modules fail-safe to "RUN". In this state the modules and their subsystems can support all operator requirements. If the engine run flag serial data is False, indicating that the engine is not running, the modules fail-safe to "OFF-AWAKE". In this state the modules are constantly checking for a change status message on the serial data circuits and can respond to both local inputs and serial data inputs from other modules on the vehicle.

On this vehicle the following modules receive Serial Data Messages for power mode status:

Driver Door Module (DDM)
Passenger Door Module (PDM)
Radio
Discrete Ignition Signals
Those modules that have discrete ignition signal inputs also remain in the state dictated by the last valid PMM message received on the serial data circuits. They then check the state of their discrete ignition input to determine the current valid state. If the discrete ignition input is active, B+, the modules will fail-safe to the "RUN" power mode. If the discrete ignition input is not active, open or 0 voltage, the modules will fail-safe to "OFF-AWAKE". In this state the modules are constantly checking for a change status message on the serial data circuits and can respond to both local inputs and serial data inputs from other modules on the vehicle.

BCM Wake-up/Sleep States
The BCM is able to control or perform all of the BCM functions in the wake-up state. The BCM enters the sleep state when active control or monitoring of system functions has stopped, and the BCM has become idle again. The BCM must detect certain wake-up inputs before entering the wake-up state. The BCM monitors for these inputs during the sleep state, where the BCM is able to detect switch transitions that cause the BCM to wake-up when activated or deactivated. Multiple switch inputs are needed in order to sense both the insertion of the ignition key and the power mode requested. This would allow the BCM to enter a sleep state when the key is IN or OUT of the ignition.

The BCM will enter a wake-up state if any of the following wake-up inputs are detected:

Any activity on the serial data line
Hatch ajar switch
Hatch release switch
Door ajar switch
Key-in-ignition switch
Monitored load relay
Park/fog/headlamps are on
The BCM experiences a battery disconnect and reconnect condition. [This is why bad ground connections, or loose or dirty connections can lead to current draws. The first step of any fix of the current draw problem is to make sure that all of the ground locations are clean and solid and also the batt cables to the batt, starter, and fuse block.]
The ignition is turned ON.


The BCM will enter a sleep state when all of the following conditions exist:

No activity exists on the serial data line.
The ignition switch is OFF.
No outputs are commanded.
No delay timers are actively counting.
No wake-up inputs are present.
If all these conditions are met the BCM will enter a low power or sleep condition. This condition indicates that the BCM, which is the power mode master of the vehicle, has sent an OFF-ASLEEP message to the other systems on the serial data line.
Power Requirements
The BCM has two main power feeds (high and low current), and two main grounds. The low power feed (battery 1) is used to provide power for the BCMs logic and internal driver operation. The high power feed (battery 2) is used to provide power for systems that draw higher amounts of current (motors, lights, etc.). The BCM will operate properly with a system voltage of 9.0-16.0 volts. If system voltages exceed 16.0 volts the BCM will provide protection by disabling certain functions that may be damaged due to higher than normal system voltages.

Monitored Loads
In order to minimize any battery rundown, the BCM can detect if certain electrical loads have been left ON after the ignition is turned OFF and the driver has left the vehicle. When the BCM detects that the ignition has been cycled to the OFF position, the BCM immediately checks the status of the load monitor input. If the BCM detects that a load is present (grounded input), the BCM turns ON the load monitor relay for 15 minutes. If after 15 minutes the BCM still recognizes that a load is present, the BCM will turn OFF the relay, removing the battery voltage from the loads. The BCM continues to monitor this circuit for a switch transition. The BCM will again turn ON the relay for 15 minutes if a switch transition occurs.

Load Shed Control
The BCM can turn off the rear window defogger and heated outside mirror electrical loads when the vehicle is in a condition where these loads may discharge the battery. The BCM will also remove these loads when engine demands are greater.

Interior Lamp Over Voltage Protection
The BCM disables the interior lamp bulbs when the system voltage is above 18.0 volts in order to extend the bulb life.

Driver in Vehicle Detection
Using the ignition switch/door ajar inputs, the BCM can detect whether or not the driver has left the vehicle. If the ignition is turned to OFF with no door ajar status detected, the BCM assumes that the driver is in the vehicle. As soon as the BCM detects a door ajar, the BCM will assume the driver has left the vehicle. The BCM uses this information to determine the RAP status, then sends the status to the other systems also responsible for RAP functions.

BCM Fail-Soft Condition
If a particular BCM malfunction would result in unacceptable system operation, the BCM takes a fail-soft action in order to minimize the condition. A typical fail-soft action would be the substitution of a fixed input or output value when the BCM is unable to interpret data correctly.