Battery drain/ BCM issue?

[jhilario72]

Hi everyone, thanks for the great advice I've gotten here since I joined. I am combining my previous posts into one thread here, in hopes of getting all of the troubleshooting advice and help.

I have the following issue on my 2003 Yukon XL Denali.

1. Rear Access Open message on DIC. Rear hatch closes and locks properly.
2. Excessive battery drain (dead after 2 days), battery drain slows down considerably when I pull the Bose amplifier fuse.
3. Dome lights stay on (assuming because of the Rear Access Open error). I use the dome light bypass to keep them off.
4. To lock the truck, I have to push the Lock button on the fob one time, and then the interior lights go on, but doors don't lock, then I push the Lock button a second time and then all doors lock.

Everything, I have been reading here says, it can either be a bad lock switch/actuator on the hatch or it's the BCM.

I don't have a bi-directional scanner. Maybe my mechanic has one. What is the best way to go about troubleshooting these issues? How would the bi-directional scanner find some of these issues? What are the codes to look for?

Another question, I have is, if it is the BCM, how do I trust that another used BCM I get (like from car-parts.com) will be reliable and not have it's own issue?

Thank you everyone, for any and all advice. I bought this XL Denali used, 2003, with only 67k miles. Drives great! It has the blown rear shock air bags, but I'll fix that later with a Strutmaster conversion kit.

 

[strutaeng]

It could be that you have more than one parasitic battery drains. You seem to have already figured out the Bose amplifier one.

The front center console HVAC/radio control and instrument cluster are also known problems on some trucks draining batteries. Your mechanic should be able to find the offending circuit. Watch a YouTube video if you are doing this yourself. Once you find the circuit having a wiring diagram will be necessary (actually, it would be good to have now before starting).


I don't know on the BCM question. I've swapped mine on my 99 Silverado twice and didn't have any issues, but wiring is completely different on the '03+. The first time my mechanic did like a relearn procedure and the BCM was from the junkyard. The second time I swapped it also from the junkyard (I did an engine swap and messed up wiring causing the BCM to short out, my fault.) I had done a vats delete and didn't have to anything.

 

[swathdiver]

I learned the other day that the Car Scanner app from the Apple store can read BCM codes on our Foseal OBDII adapter. Then you can solve the codes with the help of the shop manual's troubleshooting guide.

 

[jhilario72]

Basically, I'm trying to figure out if I have individual problems (Amp battery drain, bad rear hatch switch/sensor) or I have just one problem (bad BCM).

Thanks!

 

[jhilario72]

For example, how would I know the Rear Access Open issue is due to a bad rear hatch sensor/switch or a bad BCM? Also, how would I know if the Bose amplifier parasitic battery drain is due to a bad amplifier (short) or a bad BCM (keeping the amplifier awake).

 

[strutaeng]

You need a wiring diagram for those components. I recommend a monthly subscription to AllData DIY. It's like $20 and get access to ALL wiring diagrams (engine, transmission, body, etc.) and services bulletins and procedures for your specific vehicle for a full month.

Once you have the wiring diagram you can figure out how to look for switches, wiring, pinouts, etc., check for voltage, grounds, jump wires as necessary to rule out bad switch, wiring or faulty BCM.

 

[jhilario72]

I learned the other day that the Car Scanner app from the Apple store can read BCM codes on our Foseal OBDII adapter. Then you can solve the codes with the help of the shop manual's troubleshooting guide.

I just got the Foseal, so I'll check it out. Do you know where I can find a list of BCM codes?

 

[jhilario72]

I just got the Foseal, so I'll check it out. Do you know where I can find a list of BCM codes?

I subscribed to AllData, can I find the BCM codes there?

 

[jhilario72]

For the battery drain issue, I found the following. If I leave the amp fuse in, battery is dead after 2 days (down to 8 V). I jumped it and drove drove the car for 30 min. I removed the amp fuse and monitored voltage daily without starting it. It went from 12.6 V fully charged to 12.3 V after 5 days.

1. Is that reasonable voltage drop.

2. What could be bad in the amp to drain so much?

3. I'm thinking of getting a luxe Bose amp off of eBay and swapping it out. Is that a good idea or should I investigate wiring?

Thanks.

 

[rzabel]

Hi everyone, thanks for the great advice I've gotten here since I joined. I am combining my previous posts into one thread here, in hopes of getting all of the troubleshooting advice and help.

I have the following issue on my 2003 Yukon XL Denali.

1. Rear Access Open message on DIC. Rear hatch closes and locks properly.
2. Excessive battery drain (dead after 2 days), battery drain slows down considerably when I pull the Bose amplifier fuse.
3. Dome lights stay on (assuming because of the Rear Access Open error). I use the dome light bypass to keep them off.
4. To lock the truck, I have to push the Lock button on the fob one time, and then the interior lights go on, but doors don't lock, then I push the Lock button a second time and then all doors lock.

Everything, I have been reading here says, it can either be a bad lock switch/actuator on the hatch or it's the BCM.

I don't have a bi-directional scanner. Maybe my mechanic has one. What is the best way to go about troubleshooting these issues? How would the bi-directional scanner find some of these issues? What are the codes to look for?

Another question, I have is, if it is the BCM, how do I trust that another used BCM I get (like from car-parts.com) will be reliable and not have it's own issue?

Thank you everyone, for any and all advice. I bought this XL Denali used, 2003, with only 67k miles. Drives great! It has the blown rear shock air bags, but I'll fix that later with a Strutmaster conversion kit.

Thought I'd try to refresh this thread since I don't see a solution yet and I have some of the same issues and haven't found a closer post on here. I have issues 1, 3 and 4 above. I've had excessive battery drain in the past but solved that by removing PO's aftermarket remote start. My number one is Right Rear Door Ajar instead of Rear Access Open. The interesting thing on my vehicle is that the problems come and go for no reason! And they come and go together. I know when I get the Right Rear Door Ajar message that the interior lights won't work right. Also associated is the feature that keeps some accessories working for a short time after you turn the engine off (stereo, power windows) until you open the door. All these come and go at the same time. So, is it the door switch causing all of this? Or a bad ground somewhere? Or the BCM?