Apach 031
TYF Newbie
- Joined
- Jun 20, 2021
- Posts
- 19
- Reaction score
- 40
Hey everyone. 2008 Yukon Denali, 6.2 AWD. I have seen a ton of posts on this topic, but rarely have seen anyone post a follow up with the resolution. So here is what worked for me.
The issue I was having is as follows: after startup, vehicle would run fine for between 5 and 10 minutes. Once the temp gauge was up to normal, within about 2 minutes, the door chime would start ringing repeatedly, the check engine light would come on, stabilitrak would turn off, service suspension message would turn on, the speedo and tach would jump around like crazy, and the vehicle would lock into 2nd gear (limp home mode I think?). This went on for several months, initially at random times, and eventually, everytime I used it. Multiple codes would show, and the truck would stay in limp home until it cooled down, AND I cleared the codes. They were somewhat random which codes would show, but the 2 consistent ones were P0700, and U0073.
Checked everything I could, under the assumption it was a ground issue. Did the big 3 upgrade. Battery was a little weak, so I replaced it. Unplugged every control module, cleaned connection, and re-installed. Cleaned and re-installed the ground under the drivers seat.
What finally worked was a combination of 2 things. I did them both at the same time, so I can't be sure which was the magic bullet. First, the wiring harness that goes into the tail of the transmission. It leaves the transmission, and immediately loops up, and goes overtop of it. The Y pipe for the exhaust is directly beside it, and there is a heat shield bolted to the side of the transmission. In my case, the wire loom was laying against the heat sheat, and about 4 inches of it had melted away, leaving the wires against the shield. I couldn't see anyplace where the wire insulation had melted through, but I wrapped them all in black tape, put a new piece of wire loom on, and snap tied to the side of the trans so they could no longer touch the heat shield. In my mind, this was the solution.
The other thing I did was, I unplugged my pioneer stereo from the OBD port. My stereo has a built in code reader. It has been plugged into the port for about 2 years, but I have seen other people have issues with cheap OBD scanners messing with the ECM, so I unplugged it for good measure.
Been 2 weeks of daily driving, no repeat of the issues so far.
Happy driving.
The issue I was having is as follows: after startup, vehicle would run fine for between 5 and 10 minutes. Once the temp gauge was up to normal, within about 2 minutes, the door chime would start ringing repeatedly, the check engine light would come on, stabilitrak would turn off, service suspension message would turn on, the speedo and tach would jump around like crazy, and the vehicle would lock into 2nd gear (limp home mode I think?). This went on for several months, initially at random times, and eventually, everytime I used it. Multiple codes would show, and the truck would stay in limp home until it cooled down, AND I cleared the codes. They were somewhat random which codes would show, but the 2 consistent ones were P0700, and U0073.
Checked everything I could, under the assumption it was a ground issue. Did the big 3 upgrade. Battery was a little weak, so I replaced it. Unplugged every control module, cleaned connection, and re-installed. Cleaned and re-installed the ground under the drivers seat.
What finally worked was a combination of 2 things. I did them both at the same time, so I can't be sure which was the magic bullet. First, the wiring harness that goes into the tail of the transmission. It leaves the transmission, and immediately loops up, and goes overtop of it. The Y pipe for the exhaust is directly beside it, and there is a heat shield bolted to the side of the transmission. In my case, the wire loom was laying against the heat sheat, and about 4 inches of it had melted away, leaving the wires against the shield. I couldn't see anyplace where the wire insulation had melted through, but I wrapped them all in black tape, put a new piece of wire loom on, and snap tied to the side of the trans so they could no longer touch the heat shield. In my mind, this was the solution.
The other thing I did was, I unplugged my pioneer stereo from the OBD port. My stereo has a built in code reader. It has been plugged into the port for about 2 years, but I have seen other people have issues with cheap OBD scanners messing with the ECM, so I unplugged it for good measure.
Been 2 weeks of daily driving, no repeat of the issues so far.
Happy driving.
