JoeBobBriggs99

I am at a complete loss. I like to think I’m pretty good at diagnostics and usually hit the problem right on the button, but my 1999 Suburban has got me stumped and I’m now resorting to throwing parts at it.

I’m not sure where to start because I have been doing a lot of work on this vehicle for about a year now, but I’ll get right to the nitty gritty…

Several weeks ago I was about to go out to a job site, so I went and got into the suburban, started it and backed it into the driveway so I could load some additional tools I needed into the back. I turned it off, loaded up, and got back in. Stuck the key in, turned it, no crank…nothing. I had power to all accessories, just no crank.

After I loaded up a different car and then got back from the job, I started to look at it. All fuses were good. All relays seem to be working just fine. I noticed when I stick the key in and turn to position 1 I get a light on the PRNDL on the instrument cluster. When I turned the key to position 2 (accessory) and position 3 (run) the PRNDL light goes out and when I try to crank…nothing. I pulled out my scan tool and checked. No unusual codes other than one for the steering angle sensor (haven’t gotten to that one yet.). So, here I am. I’ve now checked the transmission wiring harness for continuity to the ECM. I’ve replaced the Transmission Range Switch wire pigtails out with new ones. I’ve replaced the Transmission Range Switch altogether. I’ve swapped out the Ignition Switch. I’ve pulled and inspected the instrument cluster. I swapped the old ECM back in (See below). All of it checks out!

And even with all that, it gets a bit stranger. One day I had another job to go to and went out to see if it would start. Sure enough, it did! So, I left it running, turned on the A/C and went inside for a moment and came back out and got in it. When I put it in drive and pulled away the PRNDL cluster light went out again and the A/C disengaged. I went ahead to my job but did not turn the vehicle off. By the time I was done, the vehicle was missing badly as well. I drove it home and ran the scan tool on it. I had the following codes…

• P0300 - Misfire
• P0713 - Transmission Fluid Temperature sensor circuit high input (Had that one for a while, I think the sensor is bad since the wiring tested out good)
• P1381 - No communication with brake control module
• U1041 - Lost communication with Electronic Brake Control Module
• U1192 - Lost class 2 communication with passlock/Electronic Variable Orifice (I’ve had this code for a bit too and didn’t cause any issues)
• C0472 - Steering position & rate of change sensor circuit low.
• U1016 - Lost communications with ECM

Since this, I have been able to start it a couple of times where after a few minutes of idling, I get the same symptoms of no PRNDL cluster light and A/C cuts out. I also have found that right around that time I get an electronic burning smell for just a few moments. I have not been able to locate the smell because once it is gone, nothing continues to smell like it.

Like I said, I’ve replaced the Ignition Switch, Transmission Range Switch and it’s pigtails and inspected as much of the wiring as I can get to.

Now for the background… When I first got this truck, I pulled the engine and transmission. I resealed the engine and put a few upgrades in it. I also replaced the transmission with a rebuilt. I also replaced the ECM because the original was coding out when the transmission was trying to shift to 3rd gear. The truck ran perfectly for months after all of these changes until that one fateful day.

Anyone have any ideas? I am so stuck here.