03 z71 tahoe parasitic drain

[ncalvo]

I have had my tahoe for over 10 years now, and the electrical gremlins are really haunting me.

Currently (no pun intended) I have a parasitic drain, and narrowed it down to the info circuit.
Interestingly, when I pull the info fuse out, and reinstall, it appears the drain disappears. It also seems the drain is not always present.

Has anyone had this issue, or can any thoughts point me in a direction to investigate further?



Some background:

Lately I have to jump my car every 1-2 days.

In the past I have had battery drains that I seemed to fix, or avoid.
About a year and a half ago I noticed my radio would not turn off, the aux power was constant hot. When I redid my entire audio system with a new amp, speakers, sub, and wiring, I ended up running a wire from a tow accessory connection near my brake pedal. That was a simple alternative.

In the past I had also noticed, just using my fingers, if I were to try and touch the ignition cylinder with or without the key in, I could turn it ever so slightly and the battery light on the dash would light up. Since fiddling with it, taking the cylinder out and putting it back in, I can't seem to repeat that.
Maybe a new ignition lock cylinder and switch? I have those sitting on the work bench but haven't gotten to it.

I also had the cluster repaired last year, I wanted the bulbs replaced and to be bright again, I didn't know I had issues in the cluster but the motors were replaced and several grounds were fixed to my knowledge.

I am not sure if any of these things are related. I could use any thoughts or experience if anyone has any.
I need to be able to rely on this truck again, it's my daily driver.

 

[Big Mama]

Welcome from Virginia. I’m no electrical expert but others will chime in starting with a load test on your battery and checking all of your cables and grounds. Did this exist prior to the stereo?

 

[ncalvo]

Welcome from Virginia. I’m no electrical expert but others will chime in starting with a load test on your battery and checking all of your cables and grounds. Did this exist prior to the stereo?

Thanks I will have to go through and check as you described. I just dropped it off this morning at an electrical "specialist" who narrowed down the drain for me while I was at work, and picked it back up because he said he couldn't solve it. He discovered the drain would go away when he pulled the INFO fuse. He said it took him about 4 cycles of going thru fuses to even find a drain, as it was intermittent. He also said when pulling the info fuse, the drain would stop, and then putting it back in place would not necessarily trigger the drain again, it seemed to stop it.
This is a new issue, been going on a few weeks now.

The last time I had a drain on the battery it was coming from the radio, my temporary fix at the time was to pull the radio fuse and drive for months without a radio, until I redid the sound system. Rewiring the new radio off of a towing connection avoided the constant hot that my radio was getting, and the radio still conveniently turns off with the key.

 

[Big Mama]

Are you turning everything off before killing the engine? When you get your battery tested get the alternator checked too. Let’s invite more help @PNW VietVet @swathdiver

 

[ncalvo]

Are you turning everything off before killing the engine? When you get your battery tested get the alternator checked too. Let’s invite more help @PNW VietVet @swathdiver

Yes, everything shuts off with the key. My battery is a month old, tested the alternator and it is good as well.



I found this post in a post on a different forum for an 03 suburban:
QUOTE:
To sum up for anyone that reads this later and wants the short of it. Set you meter on 200millivolts. Put red and black on the top metal portion of the INFO fuse and see if you get a reading (for voltage drop). Put it on any fuse and see if you get a reading. You really should get .00 on all of them unless the computer is leaving that circuit on for something. It takes 4 hours for a .3 millivolt (or .5 amp) draw to go way on my HVAC fuse. A .7 millivolt (or 1 amp) draw never went way for me on the INFO fuse. I pulled the fuse, if you want to fix proper you will need to replace the ignition switch, have the BCM re-programmed, trace a short in the wiring of the circuit or replace the onstar module under the dash. Not sure how else to properly fix. A recall does exist for the BCM re-program.

 

[swathdiver]

Does this year have the RAP (Retained Accessory Power) system? What items are tied to the INFO circuit? Seems that something is waking up and then drawing too much power.

 

[ncalvo]

Does this year have the RAP (Retained Accessory Power) system? What items are tied to the INFO circuit? Seems that something is waking up and then drawing too much power.

This year does have the RAP system. Before rewiring my radio power, I used to be able to listen to the radio or watch dvd's after taking the key out but before opening the car doors, for around 10-15 minutes before it would power off.
I just looked at the fuse diagram and see that the INFO circuit seems to provide power to: Vehicle Communication Interface Module (VCIM), Rear Seat Entertainment (RSE) Assembly, Remote Playback Device-CD Player

It does sound like this is on the right track.

 

[ncalvo]

I remember referencing this youtube video last year

It covers some of the wiring of the rap relay and the relationship to the BCM.
Although my issue is not the same as in the video, the video covers an issue with the door switch not triggering. My door lights all function properly.

I am not 100% sure that the drain on my info circuit is related to the issue with my radio power being constant hot, but they totally could be.

 

[swathdiver]

This year does have the RAP system. Before rewiring my radio power, I used to be able to listen to the radio or watch dvd's after taking the key out but before opening the car doors, for around 10-15 minutes before it would power off.
I just looked at the fuse diagram and see that the INFO circuit seems to provide power to: Vehicle Communication Interface Module (VCIM), Rear Seat Entertainment (RSE) Assembly, Remote Playback Device-CD Player

It does sound like this is on the right track.

Ok, getting warmer! Is your rewired radio on this circuit at all? We have heard of the VCIMs failing and causing a draw before.

 

[OR VietVet]

I did not see the amount of measured drain yet. Did I miss that?

Found this explanation if it helps:

Retained accessory power (RAP) is a power mode that permits the operation of some accessories for up to 10 minutes after the ignition switch is turned OFF. The RAP power mode is enabled by the body control module (BCM).

The BCM:

- Controls certain body functions.
- Sends out a class 2 message via the serial data link, which enables/disables other modules at the beginning/end of the RAP power mode.
Some BCM features, such as the interior courtesy lamps will function after the 10 minute RAP time limit has elapsed. This is normal, and does not mean the RAP power mode is malfunctioning. The BCM enables the following functions in the RAP Power Mode:

- The windshield wipers and washer through the RAP/adaptive cruise control (ACC) relay.
- The right and left power windows through the RAP/ACC relay.
- Any class 2 module that functions in RAP power mode and is not connected to the RAP/ACC relay, is controlled by the BCM via class 2 power mode messages. EXAMPLE: The radio works in RAP power mode because the BCM sends it a class 2 message telling it that the power mode is RAP.

RAP is disabled when:
- A door is opened.
- Low battery voltage is detected by the BCM.
- The ignition switch transitions from OFF to ON or ACC.
- 10 minutes have elapsed after the ignition was turned OFF.

The BCM monitors the ignition switch position, battery voltage and passenger compartment door status to determine whether RAP power mode should be enabled. If the ignition switch transitions from ON to OFF, the battery voltage is within the acceptable range, and the passenger compartment doors are closed, the BCM enables RAP power mode. After 10 minutes have elapsed, the BCM sends a class 2 message to the serial data network. This message commands the other modules that are power moded by the BCM to stop functioning.

RAP/ACC Relay
The BCM controls the RAP/ACC relay coil circuit using low side drive. The output of the relay is used to supply battery voltage to the windshield wipers and power windows. The RAP/ACC relay also provides voltage to the windshield wipers and power windows when the Accessory and Run power modes are selected.


Also found a way to test the relay for RAP: https://www.2carpros.com/questions/2000-chevrolet-impala-rap-breaker