Keep the faith David. Not home yet from Veterans day fun. Will call you as soon as I can. Looks like I may need to plan a road trip.

 

It may be easier to find the problem now it's really screwed up.

You could start with main power checks. With the key and lights on try these tests. Take your meter and put one lead on the negative battery post/bolt and the other on the block. Then, move the block lead to the frame.

Next, put the first lead on the battery positive post and test the other lead on the stud for the under hood fuse block and the main starter solenoid post and the power stud in the footwell fuse block.

The above is basically measuring the voltage drop "across" the main power cables. It should be a very small voltage in each test (well below 1V on the meter). If you find a higher voltage then the wire going between those 2 points is likely where your problem is.

 

guidance. I am no electrician. Sam is going to call me tomorrow. The car was running fine until we disconnected the BCM to check connectors due to intermittent IPC out. I dc'd battery before doing that. So BCM 3 plugs were disconnected after dc'd battery. I have the battery on a charger. It is 1.5 year old. After 6 hours, it is still charging. Before I started the charge, it read 11.9 volts with no load. Before this happened it was strong and read 14.5 volts idling. Never any previous hint of a starting problem Car has 19 K, no visible corrosion (as it has been in garage and never in rain) on it and all grounds and plugs I have checked are pristine. I may take the battery over to Autozone for a check by them also. There was a clicking noise coming out of the footwell after I reconnected the battery. I made sure batt terms were clean and tight. It seemed to have rapidly run it down, but 6 hours on a charger seems a bit much. Hope the BCM is not fried.

I cannot even get DIC to pull codes. Just get all those DIC messages to service and check everything. Sam says you and Bill are awesome and we will follow your leads as we try to run this down. I kind of wish I had just lived with the IPC intermittent issue. Prev owner had IPC replaced 5k ago. Did not fix the issue.
Thanks,
Dave

 

head.
I wanted to check the star connectors again. When I took grey cap off the tooth bar stayed in the plug. Like a fool, I took it out with needle nose. I know this sounds really ignorant, but which side of the spring female plug does the tooth bar seat? They have been apart so much. I notice the slot for the tooth bar is offset , so it looks like the teeth seat on the side opposite the locater slot(to far right of that side) on the white body of the plug. This is the only way the cap will snap back on easily. Am I right?
Battery after overnight charge was 13.54. After running checks Lionel suggested it is now 12.01. Checks were all below 1 volt. Recall , all these problems started after I dc'd the BCM. All wires and plugs to it seem OK on recheck.
Can the tension on the female spring clip in these plugs be increased.

I am clearly no techie and am lost in the ozone. Sam is going to call later.

 

you let me know if and how I can increase the tension on female plugs inside the star connectors. The plugs where the teeth in the grey cap seats.
Ran all the under hood powered wires tests and none were near 1volt, so I think Ok there.
Still no start and com codes and low fuel, ses , trac control, reduced power messages and BCM com codes.At least the relays and modules aren't going nuts like they were.

 

I haven't even looked at the star connector before but it appears to be a funny terminal I'm not really familiar with.

I think you should go back to basics. At the star connectors you only need to connect the PCM and BCM together for the car to start. Not much else will work but that should allow it to start. Both of those connect at the large connector. The PCM is dark green at cavity B and the BCM is light green at cavity M. Try jumpering just those together and see if the car will run. If it won't start then you've likely got another issue besides the serial bus.

 

That makes sense to me. The battery discharges very quickly when hooked up. It went from full charge to full discharge in an hour, but heard no noises from car and at least no smell or smoke.

Sam is coming this way next week, and we can try this when he is here. In the meantime, I am going to look at the fuses, but don't think they are at issue. It is back in my garage with the battery disconnected for now. Charged battery and it showed 14V after charge, so we will have a good battery to start checks.

 

You could try pulling every fuse and see if the drain goes away.

I would recommend using your multimeter to measure the discharge current but the current may be too high and damage the meter. Possibly just monitor the battery voltage.

Are you sure the battery is good? I can't recall if you had it load tested but doing it again might not be a bad idea. That voltage drop may not be a drain but a bad battery that just drops voltage as soon as it's loaded.

If you start mass pulling fused then take some good pictures first.

 

PLEASE have the battery tested for reserve capacity and CCA!

It SHOULD NOT run down that fast! PERIOD! Once its proved good or bad proceed by getting another battery or reinstalling the proved good battery.

You also cant pull ALL the fuses and properly test for excessive current draw. The BCM needs to be able to LOAD DROP and put the car into the SLEEP MODE.

To check for sleep mode current draw, you need to disconnect the negative battery terminal. Insert a 10AMP DC Amp meter in series between the neg BATT terminal and the Neg BATT cable:

Use a DC AMP Meter on the 10 AMP scale and put the amp meter leads in SERIES between the Negative battery cable and Negative battery terminal.

It will initially read approx 8 amps and should drop off to minimum amps with approx in 2 min to 12 min.

The correct minimum reading should be 20-25 milliamps or 0.02 amps. Post results









What you can do to eliminate everything under the hood at once is open the Under hood fuse center cover. On the side of the fuse box will be the B+ battery terminal. Under that terminal NUT, will be TWO battery wires. One comes from the battery and the other one is the main B+ wire for the PASSENGERS FOOT WELL Fuse Box.

Remove the battery NEG wire for safety before working on the hot B+ terminal wires.

If you remove the wires from the under hood fuse box B+ terminal and use a nut and bolt that fits in the two wire terminals and temporarily connect the two wires together. Insulate the the connections. When the wire are removed from the under hood fuse box B+ terminal, that entire box is dead.

Removing power from the underhood fuse box eliminates the current draw from ALL the fuses in that box. It will still allow the BCM to do its sleep mode load dropping and you can still measure the loads on the passengers fuse box. The ONLY thing that is still connected under the hood will be the starter solenoid and the alternator.

If you have an excessive current draw, it will be in the passengers fuse box loads. and or the starter solenoid and the alternator.


Common causes for the excessive draw will be Drivers or passenger seat lumbar and or seat motors, Bose Amp, Rear window defroster circuit.

Hope this helps

Bill

 

Picture of the under hood B+ terminal

NOTE!! I have three wires because I added a feed for my heated seat hot wire. You will NOT have that third wire!

 

Just a caution about that meter connection. If something is drawing enough power to drain the battery in an hour it may be enough current to blow-up or melt-down the meter.

I believe a good C5 battery would have a reserve capacity in the 100 minute or higher range which is the time a 25A current draw would take to discharge the battery. In other words, your car would require a rather high current drain to discharge the battery in an hour, likely in the 40A to 60A range (think 600W of lighting as the load). I would think you'd see a pretty big arc at the battery terminal when you connect or disconnect it.

 

100% Agree... Test battery and then look for a very high draw. The C5 will always draw an arc when connected but nothing very big.

Install a 10 AMP fuse between the NEG battery terminal and the battery cable connector. If it blows the fuse, you have a draw larger than 10 amps!

NOTE!! If you make a slow poor connection, current draw slightly below 10 amps can blow the 10 amp fuse.

 

Thanks guys. I am going down to see him next Wednesday and I will first do some continuity checks looking for ground shorts or stuck relays, etc, before connecting a battery. When I hook it up I will be installing an amp meter in series to see what the current is. It has fuses internally to protect it but I will be installing an external fuse also. Need to resolve this mystery battery issue first and then we will attack the original problem. He said the battery had a normal small spark when he connected, not something like a high amp flow. The auto store gave him a new battery and I am pulling mine out of my car to have on hand also.

 

Good Luck

Dave has my cell number if you need any help.

Bill

 

Sam will be here Wednesday. New battery at full charge and disconnected until then.

I just keep sitting here puzzling over the fact that disconnecting the BCM plugs with the battery disconnected to check them could cause all this. Oh well. It will be interesting to see what solves it. "Study , diagnose then treat !!" Hope it is not going to be a total walletectomy !
Dave

 

The guys helping you are very good, when you connected the ignition connector and left out or slipped off the BCM wire it is possible that a fuse let go after connecting it again. not sure

I had an issue with my Avalanche where I had to replace the PCM, doing so caused a battery light to stay on, with Bill's help I checked the fuse, it looked good but it was bent inside which didn't seem right even tho is was complete, replaced and reset battery connection and light went away. This said, when you look at the fuses make sure they look solid and straight, check all BCM fuses and related ones as well.

The good thing is having someone help you.

 

grateful that Sam, Bill , Lionel and others are out there helping with this.
I fear that I may have powered up the car with that ignition b/w wire improperly seated in the BCM possibly in one of the"not used" ports like A 5 instead of A 3 where it belongs. The only problem I had before that was the longstanding IPC intermittently going off and coming back up. So I may have fried the BCM. And, maybe the BCM was at the root of the IPC issue.

Sam is going to assist with checking out all the circuits before I replace the BCM, which I think will require reprogramming for some of the options on the car like the memory and power steering wheel.

I visually inspected the BCM fuses and they look fine, but so do I from
ten feet away !!
Oh well, we live and learn, and I am learning a lot from you folks.

Thanks for the input and support.
Dave

 

Thanks for the input. I plan to test every possible problem related fuse, circuit, and relay as necessary. We will find the problem with the Forum help.

 

Dad

This issue seems have changed from the first post. Start from BASICS. Get ALL the symptoms noted before you attack one item

If it were me, I would check the battery current dray straight off and see if its excessive. That is most likely NOT the main cause of the issue BUT,,, it make trouble shooting tough if it kills the battery.


Check for fuel and spark during CRANKING. When you check for fuel, make sure that you let the fuel stream run long enough to bleed off any built up pressure during KEY ON.


You guys let me know if I can help.

Bill

 

Sam just left.
I left you his # and, perhaps you could give him a call.

1. The rapid battery discharge was due to relay 46 rapidly cycling. Not sure of cause, but we had the star connectors disconnected when it did it. Did it with them connected also. Relay is out of car now. It seemed to be functioning OK when Sam tested it out of car.

2. Car will still not crank at all. Still have all the same messages and codes. Sam jumped the lt green and dark green, PCM/BCM, wires and it still would not crank. LSX tTuning, just told me he programmed security out of the PCM when he did the tune.

3. Sam can tell you all that he checked, but the main power feeds and under hood wiring seemed to check out OK. Battery is fine.

Again, car ran fine until I removed BCM to try to check all plugs to run down the intermittent IPC outage.


So I still have one of the best looking paper weights in Charleston !!

Thanks ,
Dave