This 2003 Chevrolet Avalanche with a 5.3 liter VIN “T” engine was towed in with the complaint that the engine would not run. I went to check codes and data and found that communication to the PCM was down. I checked all of the fusees under the hood and in the interior fuse box. No problems found there. The next step was to go to the PCM located above the frame rail next to the battery. I had to remove the plastic cover and then unsnap the clip that holds it in place. That allowed enough room to disconnect the PCM harness connectors. They both have a 7 mm headed screw in the center of the connector.
I used a pocket screwdriver to depress the clips that held the covers on the back side of the connectors. The green, C2 connector only had two circuits to test, so I started there.
I was looking for the ground signals on terminals 1 and 40. I started with terminal 1, black/white wire. I checked continuity to the battery negative terminal and found it was open. Notice I used a fine tip pick attached to my multimeter lead to test at the harness connector. I also used a very gentle touch as the terminals are easily damaged.
A closer look at the test setup.
This is another test I like to use to test the amp carrying ability of a circuit. Some people use a sealed beam headlight as a load but I find that cumbersome. I must caution you that you must have a full understanding of what is connected to a particular circuit before performing any kind of a load test on it. Failure to do this may result in very expensive damage. In this case I connected one end of a fused jumper wire to battery positive. I placed my probe into the terminal to be tested. I then touched the other end of the fused jumper wire to my test probe. This is important as I did not want to create an arc mark inside the PCM terminal. The arc takes place at the side of my probe.
Since I already knew that there was an open condition on this terminal it is not very practical. If there was ground present, it would have popped the black tab up in the circuit breaker. You can do this with a fuse as well. Just can’t reset a blown fuse though. By the way I was using a five amp circuit breaker.
A closer look at the reset tab on the circuit breaker.
A look through the wiring diagrams showed that the ground terminated at the right rear of the engine. If you look closely you will see the black/white wire at the rear of the fuel rail.
There it is the end has broken off.
For test purposes, I connected a jumper lead to the wire and started the engine. It started with no problem but it would not idle properly and the “Reduced Power” message came up on the driver’s information center. Looks like there may be another problem. I checked codes and data and was coming up with what seemed like some pretty serious problems with the TAC system.
I finally decided that I better go ahead and fix this first problem before I got wrapped up in another one. As I stated earlier the wire is connected to the rear of the engine on the right side (passenger). I felt around and found it and determined I needed a 13 mm socket and ratchet with a 6″ extension.
The following picture shows where go through to find the bolt and gives you an idea of how far down it is.
The factory wire terminal and the end of the wire where it broke off at.
I stripped the end of the original wire and added about a 6″ extension to it with a new ring terminal. Sealed the connections with heat shrink tubing and bolted it back into position.
The problem with the TAC system went away once the ground was properly secured. The one thing that really bothered me about this repair can be seen in the next picture. Someone had thought that the vehicle had a starter issue and changed it. Not a big deal, but in the process of doing that they disconnected the crank sensor and did not reconnect it.
How hard is it to remember to reinstall a crank sensor connector? Well I guess it really does not matter this one is done.