1997 K2500 Suburban 454/7.4 P0122 Code

[willis68nova]

Hello,

 

I am having some issues with my suburban and they are driving me nuts! So I hope some one can help.

 

So here is what happens, when I clear the code start and run the truck I can drive a little down the road and all seems ok. But then it throws a code P0122, then all goes down hill from here, it begins to run bad and then it shifts hard through all gears. I do not get any other codes than P0122.

 

So I looked this up and it is an intermittent low voltage on the TPS circuit. I began to troubleshoot this issue:

 

Checked the three TPS wire to see if any had opens or shorts and they all toned out to where they should be. Two to the VCM and one to ground. I check the one wire that comes from the VCM for 5 volts and it had 5 volts. I also checked this wire for voltage while the truck was running and it had 5 volts. I hooked up a scan tool to the truck and the TPS have .43 volts without the pedal being pushed and 4.4 volts with the pedal being pushed to the floor. So those numbers are within range I believe. I believe I narrowed down what could be wrong, TPS, Ignition switch, or VCM? So I went the least expensive route and swapped the TPS, this did not fix it. I got an ignition switch from the junkyard (I know this isnt the best option but I wanted to test to see if it helped). When I swapped the ignition switch I was still getting hard shifts but no code until I got home and then the code came back P0122... So here is where I am at, I have a used VCM and I was thinking about getting it flashed at the dealer and seeing what happens. Does anyone else have any suggestions? Thanks for any help!

[willis68nova]

No thoughts on this? Does anyone know if the TPS 5 volt circuit is fed through another sensor or spliced from another source?

 

Mike

[Paul92H]

I am having the same issue with my 2000 3/4 ton k2500 7.4L standard trans, I've checked all the wires and changed the tps. In town just being easy on it, it seems to run okay but as soon as i get out on the highway and put a load on it is when it acts like it has a misfire. Been trying to figure out this issue for a few weeks now with no luck and it's really starting to bug me. If anyone can help it would be highly appreciative

 

Paul

[grampadirt]

I've heard the injectors can act up,might check into that.