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.