92 6.5 4l80e acting up, loose overdrive after warm up?

[J Cook]

New guy here to the forum, I hope I posted this topic in the right spot. I searched the archives, and have come to the conclusion I need to get the truck scanned for codes.

Story, 92 6.5, another 6.5 was installed into truck, since that date the auto has only had over drive till it warms up, then it kicks out. Everything looks good, no pinched wires, or burnt wires. I have drove the tuck and it just drives fine till it warms up then it shifts out of overdrive and will not go back in. The transmission fluid does not look bad or smell burnt at all, corect level and everything.

I did not try shuting engine off and promptly resarting to see if OD would come back, I will however do this when I go back to see the truck. Thank you Jon

[dieseldummy]

Most likely the throttle position sensor needs adjusted. It is under the intake manifold on the passenger side of the injection pump. To set it you need to turn the ignition on but not start. You then need to backprobe the plugin for the sensor. Probe the ground wire and the wire that goes to the ECM.(can't remember the colors) There are only 3 wires so it's not to hard to figure out. 1 is a ground, 1 is a constant 5V, and the other is the variable volt output to the ECM. IIRC, it should be around .5V at idle and when you move the throttle to full it can't go over 5V or it throws a code. As long as it's between those to specs it should go into overdrive.