Does anybody know where I can get powertrain electrical schematic diagrams for a 2008 6.2L Automatic Z51? Specifically I'm looking for engine/computer Ignition circuit diagrams.

 

What issues are you having ??

 

Thank you C5 MODERATOR for sending me those diagrams. My engine fails to shut down when STOP ENGINE is pressed. It continues to idle normally for about 15 seconds until fuel pressure drops. The ignition is still powered up even though the engine is stopped. There is about 2.5 Amps being drawn from the battery and it will drain the battery if it is not disconnected The 15 Amp ECM fuse (#11) in the engine compartment fuse block is the circuit carrying the 2.5 Amps. If I remove TCM fuse (#1) the drain goes down to about 1 Amp after a few seconds.

The engine will never shut down if the Shift Lever is anywhere except PARK. Put it in PARK and it will die in about 15 seconds.

 

Interesting !!…if you’d like to bring the car here I’d be happy to diagnose it since I have all my diagnostic equipment here or if you want to try to diagnose it yourself…I looked at your posts and it seemed you had this issue going back a few years…if you have a 12 volt test light that would be good to start…to have the engine continue to run not only do the coil packs and injectors need a 12 volt feed (2 INJ fuses #12 and 16) but also control from the ECM…if the ECM is not grounding the injector it will stay closed and the same for the coil packs..the control side of the coil packs is a digital 0-5 volt square wave which you can see with a scope…try this…take the test light and see if fuses 6,9,12,14,16 are powered with the ignition off…they are all in a row next to Relay 44…they should not be powered with the Powertrain Ignition 1 (Relay 44) de enerergized…if any of those fuses have power either the relay is stuck closed or the ECM is constantly providing a ground on pin 86 which is the control side ground…to see if you have a ground on 86 take the test light and connect it to B+…pin 86 is the rear pin closest to the fender…light should not be lit…now to see if you have control on either the coil or injector remove an easy injector connector and with the test light connected to B+ see if the injector control wire (striped wire) is flashing when the car is shut down…I’m “thinking” bad ECM maybe…I don’t like to guess…also on the crank sensor one can do a “bypass test”…on the C6 I can’t remember if the sensor gets “pulled up or down” meaning if you disconnect the sensor and there is no voltage on the signal wire you use 5 volts to pull it up and you can make the coil pack and injectors fire by tapping on the signal wire to simulate the crank sensor….the fuel pump will also operate…you can also make a coil pack fire by “tapping” on the control wire also with a test light connected to B+…will have to research the shift lever because that may be key !!…maybe remove fuse 1 and then shut the car down in other than park and see if it stays running...that fuse is hot in start or on.

 

I don't know your location. Cape Coral is all I see.
I can't tell you how many electrical problems I have fixed on this car. It doesn't let you take the shifter out of PARK occasionally. Putting it in ACCESSORY MODE doesn't automatically release the shifter from PARK. It does if I step on the brake pedal.
I only have 21,000 miles on this car and I bought it brand new in 2008. It spent most of it's life parked in my hangar at Lantana Airport until 2015. I also own a 2005 C6 Coupe, 1997 Supercharged (Procharger) C5 Coupe, and a 2000 C5 Coupe 6 Speed Trans.
I had a catastrophic ABS EBCM in January 2015. There was a hole burned through the Plug, Receptacle, and circuit board inside the BCM. I had to splice a new pigtail into the harness and get a complete ABS/EBCM from a salvage company. Everything works fine with the ABS.
I also noticed that in SPORT mode, when you are using the paddle shifters, the DIC is not displaying the gear you're in. It is displayed in the HEADS UP display.
Occaionally the screen of the CD/DVD/Radio doesn't light up even though the sound system is working. Can't play CDs any more. Only the DVD for the Navigation display works.
I was an Avionics Technician at EASTERN AIRLINES until it closed down in 1991. I have tested every fuse inside and out, and have checked each relay, even the two under the toe board on the passenger side (RUN/STOP and I don't remember the other one).
I am still searching for the problem and I'm even thinking it might be a problem with the BODY CONTROL MODULE. I show no OBDII trouble codes except P1682, and that only comes on if I let it set for a while without disconnecting the battery.
I am driving the car almost every day and I love it but I have to disconnect the battery when I go home and park it.
I really appreciate your help with this issue. I've been tryig to figure it out for several years. Last time I submitted this problem on the forum I got a bunch of really smart-*** replies and I was disappointed nobody took this igtnition problem seriously.
I seem to be the only person whose car engine keeps running when I try to shut it off. Tell me what your address is and I might take a drive over there.

 

The P1682 concerns the Powertrain Relay which I wanted you to check…PM sent.

 

C5 thank you so much for that last drawing you sent me and the troubleshooting tips. That drawing is exactly what I wanted. The problem looks to be the ECM. There is indeed a ground on pin 86. Relay 44 is closed all the time and fuses 6,9,12,14,& 16 are hot all the time. Relay 44 is not stuck, it's powered up all the time because of the ground on pin 86 of that relay. Right now it looks like it could only be the ECM that is grounding that pin of the relay. I'll check in the fuse block tomorrow to see if there is something grounding pin 86 of relay 44. It is most likely the ECM though.
Removing fuse 1did not change anything. It still continues to run in reverse, neutral, or drive. It still only shuts down in PARK after about 15 seconds. In my 2005 C6 you can shut the engine down with the gear selector in any position.
Is there a vendor you would recommend that I could send my ECM to for repair, or should I just buy one from a salvaged vehicle? I just checked with car-part.com and there is no shortage of ECMs from other GM vehicles for around $200. If I bought one from another GM vehicle would I need to get it reprogrammed for my car specifically?

 

Excellent !!…what fuse is fuse 1 you said you removed ??…don’t see that one…I said pull the relay 44 and see if it shuts down…I’m sure many dealerships would have been scratching their heads on this one…LOL !!…yes, it’s either the ECM driver stuck closed (bad ECM) or a short to ground on that wire anywhere between the ECM connector and pin 86 on the fusebox…I bet if you slowly insert the relay you can probably hear the relay “click” telling you the load side contacts are closing…now why I’d like you to do is remove an easy injector to access and remove the connector and with test light connected to B+ see if the test light illuminates probing the control wire which is the striped wire…light should not light… you can do this check when you shut down the engine before it quits…test light should go out…and it’s a good idea to see if EVERY driver on injectors and coils are “NUKED”…if that’s the case that would be unique !!…may be a good idea to check the ECM harness !!…we still have to figure why you still have “control” on the coil packs and injectors…just having power to those 2 components doesn’t mean the engine stays running after shut down…it’s as if all the drivers (pin 86, injectors and coil packs) are “stuck” closed…to test for short remove the ECM X1 connector (best to disconnect the battery first) and with the test light still connected to B+ see if the test light goes out when you remove the connector…if the test light stays lit it is a short to ground…you can do the same test with an ohm meter..one lead to pin 86 and the other to a good ground…if you show anything other than “OL” on the highest ohm scale it’s shorted to ground…for an ECM programmed to your VIN try Flagship One Inc…they are located in Lynbrook, NY just east of JFK Airport…you could fly in there…LOL !!!…yours is the E38 ECM with 2 connectors…location below (behind front right tire)…and since you have an A6 the only thing you’d have to do is a crankshaft variation relearn…if you don’t have a bidirectional scan tool I can take care of that for you…the 30 minute Immobilizer Relearn and Idle Relearn you can do yourself…interesting video below…I also want to check to see if there are any inputs on the scan tool for the start button to make sure the ECM is seeing the car turned off..I believe you changed the BCM but maybe we should do some checks there…this may be a BCM issue !!

 

I was looking at the ignition feed circuit…ECM has 3 ignition feeds and one battery feed…maybe pin 18 which is an ignition feed is powering pin 18 at the ECM from the BCM ???…it is involved in the trans, radio/nav radio and windshield wipers…see if the wipers work with the engine off !!…you said you had issues with the radio…if pin 18 which is on that X1 connector is powered with the engine off this ignition feed may be feeding the crank and cam sensor it’s 5 volts to make it operate…on the C5 that circuit between the 2 are shared !!…I’m looking at the wiper wiring and seeing if those 3 diodes (2 pictured) would have anything to do if they were blown…maybe power will back feed somewhere else that it should not…have to do some studying...didn't you have a BCM meltdown with some wiring ??...I KNOW you know how to check diodes...maybe test them...they have to go back in the same direction....just trying to figure out why they are using diodes in the wiper circuit....no mention of them in Service Info…MMMM ???

 

OK, looked at some BCM inputs…do you have Tech 2 or any high end bidirectional scan tool ??…here is what we should be seeing in OFF, ACCY, and RUN…should be reflected in the Power Mode data PID !!…this is important !!

 

Relay 44 closes as soon as you plug it in. You can hear it and feel it. I just removed X1 connector from the ENGINE CONTROL MODULE. The test light went out so the ground to pin 86 of Relay 44 is the ECM. I need a new ECM for sure. The wiring to pin 86 of R44 is not shorted to ground anywhere.
You mentioned pulling fuse 1 (TCM/TRANS) to see if the engine would shut down with the shift lever out of PARK. It still doesn't shut down unless it is in PARK. NO CHANGE.
I watched the video with the guy repairing the ECM circuit board. I did the same type of work for 6 years in the ELECTRONIC CONTROLS SHOP. at EASTERN AIRLINES.
We repaired nearly all the 385 black boxes that control the aircraft in house and recertified them to go back in service. I was the manager of that shop for the last two years we were operating. I trained all the new hires to do that kind of bench electronics repair work.
I made a typo when I was describing the ABS meltdown I had in 2015. I meant to say the Electronic Brake Control Module (EBCM) not the Body Control Module (BCM). I have never done anything with the BCM. I worried about melted insulation after seeing the damage done when the ABS system failed and melted the harness Plug, Receptacle on the EBCM, and the circuit board inside the EBCM. The largest pins in the EBCM plug which supplied current to the ABS Motor were VAPORIZED. I think there had to be a short circuit in the motor to cause that. I'll send you some pictures I took of the EBCM harness plug that I replaced when I figure out how to do that on this platform.
I only have a FOXWELL NT301 OBDII SCANNER. I don't have a sophisticated bidirectional tool to access the BCM.

 

Those diodes in the fuse block are GOOD and oriented in the correct direction. There are three of them.
I really wish I had access to those electrical diagrams you sent me. I could have fixed this car 3 years ago.I
I will order a new ECM from Flagship. I see that they don't want the old core from their ad. I'd like to get mine repaired. I could sell it on EBAY.
Do I need to get any numbers off my ECM to order the correct part from Flagship?
I can't thank you enough for sending me those diagrams.

 

Ok, so it’s the ECM coil ground then !!…Cool !!…I was rewatching a training class I did on push button diagnostics last year and a case study was on a Jeep that wouldn’t shut down like yours…the instructor said the car would start even though the FOB was far away from the car…try that…if it does start it’s possibly the RCDLR…on Jeep it’s called an RFH (Radio Frequency Hub)…think it’s the same module as our RCDLR…you can try that !!… not familiar with that scan tool...as far as the wiring get a sub on Alldata…you can get a 1 month, 1 year, or 3 year…1 month is $19.99 !!…Alldata shows your ECM P/N as 12612384 at $456.96…if you want to open up your ECM you may find a bad computer driver !!…I just had to inspect and make sure that those black boxes being installed were the correct parts if they were RII…LOL !!…also this doesn’t explain why you have injector and coil “control”…I mentioned how to check it with a test light….see if test light illuminates on injector control wire with key off…you shouldn’t.

 

Just want to say I love watching c5diag fix problems, as well as seeing a major issue get sorted out

 

Thanks but it’s not fixed yet…LOL !!

 

I did a little more poking around and found Relay 42 Wiper RUN/ACC is also closed all the time. It closes as soon as it is plugged in. The RUN/CRANK RELAY from the BCM is driving it closed through DIODE 2. RUN/CRANK RELAY is closed by the RUN/CRANK RELAY CONTROL LOGIC from the BCM. Relay 42 Wiper RUN/ACCcould also by closed by ACCESSORY VOLTAGE SIGNAL LOGIC through DIODE 1 from the BCM. Removing DIODE 1 or DIODE 2 or RELAY 42 HAS NO EFFECT ON THE ENGINE SHUTTING DOWN.
It is looking like the RUN/CRANK RELAY might be staying closed by the BCM. I had the RUN/CRANK RELAY out and tested it manually many months ago. I didn't check to see if it was being driven closed all the time by the BCM though. It is looking more and more like the problem might be the BCM. What do you think?
I had to take a few days off from this car to clear my head. I got the new ECM from Flagship One over the weekend. They sent me the wrong RELEARN PROCEDURE, for cars with regular chipped keys. I got the correct ones today but I'm not sure about trying this on my own. I don't have the scanner equipment for the 10 Minute RELEARN. I might need to come and see you.

 

You could check the run/crank coil ground the same way you checked the Powertrain Relay…could be a BCM but unfortunately you don’t a scan tool to check the power modes…so what’s happening with the new ECM…is the Powertrain Relay still energized ??…I posted the 30 minute Immobilizer Relearn procedure….the relearn procedure I posted is from the 08 Service Info…let me know how it’s going !!