Did I lose my ECM? 03 Yukon dead in the water

[Elmerwood]

First post here but a little background first. I've got a 2001 Silverado standard cab, 2006 2500HD Duramax with 350k on it and just snapped up my friends 03 yukon Friday night to have a 4wd for my cabin trips. The vehicle I'm having issues with is my 2003 Yukon equipped with the 5.3 engine. Friday evening after loading up I noticed the dash displaying "rear access open" even though it was closed and I double checked it. Friday's drive up the hill was smooth no issues. Saturday evening rolls around and everything seems normal and I go to open the rear glass hatch and the button is already half depressed. It should be sticking out past the bezel and it already pressed in. I try pushing it a few times and seems sticky and won't open. We drive to the hardware store to get some supplies and on the way back I lose all accessory power ( stereo, power windows, power locks etc). Dash lights up like a Xmas tree with all the lights and messages like "service 4wd" "unknown driver". It's still running at this point. 20 minutes later everything goes back to normal while driving. 2 minutes later back to no power but still driving. Parked at my cabin and took battery negative off to look for issues and every time I touch it to negative post I can hear what I think is that rear hatch glass solenoid fire off repeatedly then stop. I put on the charger for 15 minutes before going to dinner thinking maybe the battery is getting low. After 15 minutes on the charger it started fine with everything looking normal. Half way to dinner lose all power again. I park at restaurant and go to start after dinner and it starts and immediately dies. Dash reads "unknown driver" no aux power to locks windows etc. Had to leave it there overnight. Sunday took the battery to auto parts store to test and was told it's too weak to test so I just bought new one. Replaced old with new on and same thing happens, it starts and dies immediately. I start a google search and I start to think maybe my issue is with the passlock system. I was reading about if the voltage drops when doing the circuit test it puts the vehicle into a anti theft mode. I hade my spare key so I tried that as well with same results. I had no choice and had to have the vehicle towed home. Monday I load.it.on my flatbed trailer and take it to my shop where I start to try the reset where you leave ignition on for 10 minutes off for 10 seconds process with no luck. I checked every fuse for continuity with a meter and then pulled every fuse and checked to be sure I didn't miss anything. Got sick of change my tail so went and grabbed my friend Sanp On Solus scanner. It couldn't communicate with my vehicle. I tried multiple times and checked the lighter fuse. I checked.voltage on the OBD2 pins as well. So to double check I plugged scanner into my diesel and worked fine. I tried a simple scanner on my yukon to see if it liked a different scan tool and it wouldn't read it as well. So now I'm at a stand still. Does anyone have any suggestions for me to try or look into?

 

[OR VietVet]

Welcome to the forum from Oregon. You did not say where you are at but with you going to a cabin, I am going to assume, I hate doing that by the way, that you live where snow is and likely have salt on the roads. The first things I would have checked is part of what you have already done but I would do these checks for ground problems that these NBS rigs are known for. here is a link: https://www.fixmyoldride.com/Chevro...e7e5cd24ed24635&at_ab=per-2&at_pos=3&at_tot=4

 

[Elmerwood]

Welcome to the forum from Oregon. You did not say where you are at but with you going to a cabin, I am going to assume, I hate doing that by the way, that you live where snow is and likely have salt on the roads. The first things I would have checked is part of what you have already done but I would do these checks for ground problems that these NBS rigs are known for. here is a link: https://www.fixmyoldride.com/Chevro...e7e5cd24ed24635&at_ab=per-2&at_pos=3&at_tot=4

Good morning from California. I live in the central valley but have a house in the hills that I get to escape to every couple weekends. Thanks for the link . I've also like the link suggested check both the power and negative cable. I haven't pulled them off and inspected but I have check everywhere they connect and the connection points were tight and the cables were tugged to see if they had come loose from their crimps. I have a friend who's Toyota master tech and a Chevrolet tech before that and ran my issue by him. He's leaning towards ECM failure unfortunately. If I can make it to my shop today I may try removing and giving those cables a good once over and cleaning before and reinstall.

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics, please.

You have already received one reply and suggestion, and other folks will chime in.

 

[OR VietVet]

Good morning from California. I live in the central valley but have a house in the hills that I get to escape to every couple weekends. Thanks for the link . I've also like the link suggested check both the power and negative cable. I haven't pulled them off and inspected but I have check everywhere they connect and the connection points were tight and the cables were tugged to see if they had come loose from their crimps. I have a friend who's Toyota master tech and a Chevrolet tech before that and ran my issue by him. He's leaning towards ECM failure unfortunately. If I can make it to my shop today I may try removing and giving those cables a good once over and cleaning before and reinstall.

I am sure your tech friend will agree that the ECM are mostly bullet proof and hardly ever go bad but yes, they can go bad. Here is another interesting link: https://www.tahoeyukonforum.com/threads/another-big-3-upgrade-with-questions.111196/

 

[TJ Baker]

I have a similar 2005 5.3 Yukon.

"Unknown driver" to me suggests an issue with the BCM or communications between BCM and ECM.

Your 2003 Yukon will be using the SAE J1850 VPW protocol on the class 2 serial data network. No canbus there. OBD2 port should have 12 volt power on pin 16, ground(s) on pins 4 and 5, and the data is carried on pin2.

 

[Elmerwood]

*** EDIT *** forgot to mention that after I put the new battery in the vehicle Sunday morning it was completely dead Monday morning when I loaded it on my trailer.

@TJ Baker I'm pretty sure I checked that but I'm going to give my positive and negative cables a once over again today and ring out that OBD2 port. I can check voltage on pin 16 and continuity on 4&5 to ground, but should I check voltage on pin 2 or could this cause problems?

 

[TJ Baker]

*** EDIT *** forgot to mention that after I put the new battery in the vehicle Sunday morning it was completely dead Monday morning when I loaded it on my trailer.

@TJ Baker I'm pretty sure I checked that but I'm going to give my positive and negative cables a once over again today and ring out that OBD2 port. I can check voltage on pin 16 and continuity on 4&5 to ground, but should I check voltage on pin 2 or could this cause problems?

Won't cause problems trying to read a voltage on pin 2, but there is little you can learn there. The voltage there fluctuates far to rapidly for a multimeter to see and react to. At most, depending on data traffic you might see a transient volt or two. Here is a youtube where I display what a multimeter sees on a class 2 serial data line with some traffic on it.

 

[Camarochief]

can you communicate with all the other modules??? are all the warning lights working???

 

[Elmerwood]

can you communicate with all the other modules??? are all the warning lights working???

This is what the dash looked like when I lost all accessory power but was still able to drive the vehicle. I'm not sure.i follow you on if I can communicate with the other modules or not. I have tried 2 scanners and both won't connect/communicate with the vehicle.

 

[Elmerwood]

@TJ Baker thanks for the info. I checked my OBD2 port and pin 16 had 12V, pin 4 & 5 had continuity between each other and individually to a ground, pin 2 reAD 10.58 volts both times I checked it which seems odd when checked against your video.

 

[Elmerwood]

Tonight I tried videos I've seen "resetting the ECM" by placing the key in the on position for 10 minutes and then to the off position for 10 seconds. This process was repeated multiple times with no change in the vehicle. One thing I did notice is that when I turn the key off after leaving it on for 10 minutes the display would read different numbers each time. One time the display reads 64 the next time it reads 75 And the next time it read a zero on each end of the display. Does that sound familiar to anyone that there's a issue?

 

[BG1988]

10.58vDC !!!?!?


Hint:


check the battery
it's completely dead or flat... or one of the cells went bad

have it load tested



even in your photo it says 9 bolts of electricity ...

BATTERY is bad


it should be reading 12.3-12.5v (when off) and 12.8 to 14.8v ish(when running)from the OBD port..



OBD2 ECM only has 5v(for sensors) or 12volt rails nothing else

 

[Elmerwood]

@BG1988 in that picture of the dash, that was the last time.the vehicle was running and gauges went nuts. The only gauge that was.working was the speedometer, the others pegged to the left.

That was Saturday. I put a brand new batter in on Sunday and has died twice just sitting in the vehicle so I'm assuming I have a parasitic drain since this has all started.

Tonight I put the battery on the charger and got the voltage up to conduct some testing. Those numbers earlier were the readings from the OBD2 port tonight. Pin 2 had 10.58 volts.

My display when I turned the key off tonight was displaying odd numbers.

 

[Elmerwood]

The numbers only appear for a.very short time so I had to take a video to capture them. This one reads 75. Another time it read 64 and one time a zero at each end of the display.

 

[BG1988]

@BG1988 in that picture of the dash, that was the last time.the vehicle was running and gauges went nuts. The only gauge that was.working was the speedometer, the others pegged to the left.

That was Saturday. I put a brand new batter in on Sunday and has died twice just sitting in the vehicle so I'm assuming I have a parasitic drain since this has all started.

Tonight I put the battery on the charger and got the voltage up to conduct some testing. Those numbers earlier were the readings from the OBD2 port tonight. Pin 2 had 10.58 volts.

My display when I turned the key off tonight was displaying odd numbers.

hmm

error code

• GM MAP sensors do not commonly fail
• Due to erratic engine vacuum, other engine performance problems can cause a code 64 to set

75 Service air conditioning let us know if you get any others

check the ECM/BCM fuse maybe even replace them even if it looks ok...



it could be a faulty capacitor on the ECM if this fixes it then it could be that ... pull the ECM and bring it in the house to "warm it up" Do not put it in the oven ... just becareful as the pins get damage easy

 

[TJ Baker]

@TJ Baker thanks for the info. I checked my OBD2 port and pin 16 had 12V, pin 4 & 5 had continuity between each other and individually to a ground, pin 2 reAD 10.58 volts both times I checked it which seems odd when checked against your video.

Under no circumstances should you see a voltage that high on the class 2 serial data bus! That is outside the range of acceptable values. I would guess a wiring harness damaged somewhere or a module gone bad. My first thought would be damaged wiring which could also be causing your parasitic drain. One approach would be to locate the data bus splice comb under the dash and remove the comb, then check each individual wire to see where that 10.5 volts is coming from. This could point you in a direction for locating the trouble area.

 

[TJ Baker]

It sounds like your issue began with the liftgate. I am not as familiar with the Tahoe/Yukon as the smaller cousin, the Trailblazer/Envoy. In those vehicles the wiring from the body to the endgate/liftgate is notorious for wiring damage from years of opening/closing. Often no external signs of the damage can be seen. Big guess here on my part, but if you were having issues with the hatch, and a power wire shorted or heated enough to melt insulation and get crossed up with a data wire in the same bundle you might see the kind of things you are seeing here.

With 10.58 volts on your serial data line there will be absolutely no communications happening. No crank, no start, no nuthin!

 

[Elmerwood]

I think I need to do what this gent wrote up.

https://www.iatn.net/forums/13/54612/class-2-data-bus-shorted

 

[TJ Baker]

I think I need to do what this gent wrote up.

https://www.iatn.net/forums/13/54612/class-2-data-bus-shorted

Yep, that's about what I meant when referencing the splice comb