Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
This truck came in in limp mode with active P2135 throttle position mismatch code, It had a new reman throttle body installed, new batteries and a new alternator. Checked output voltages of TPS1 and TPS2 with a scope and found that TPS2 would have consistently erratic readings when (0.0v-1.1v) when at idle. TPS1 would stay at ~1.1v at idle at the same time. The inconsistency would only happen at idle, so I ordered an OEM GM throttle body. I also noticed the batteries (2 battery starting system) were on individual grounds, so I added a jumper between them to tie them together better. Code went away and was no longer in limp mode. I figured it was a faulty reman considering the issue was TPS voltage in a specific throttle position.
3500 miles later, came back with the same issue... I ohm checked all 8 wires to the Throttle from the TAC module, all had 0.1 ohm. Checked battery +/- at the TAC module with the scope while also having the scope back probed into TPS2, the issue continues with 14.2v battery power steady and 0.0v negative readings on the scope. I got the throttle replaced under parts warranty and the issue stayed.
I decided to eliminate the wiring and added an over lay for testing for all 6 TPS wires from the TAC module (2- 5v supply, 2- signal return, 2- low ref) issue remained and would not clear. I decided to order a TAC module because it does drop out the 5v signal for TPS2 which is what causes the signal return to drop.
Today I installed the TAC module, and still have the same active P2135 with the 5v ref dropping in and out for TPS2. I'm out of ideas at this point. I also will attach a picture of my scope readings here in the next post...
If possible, decrease the time base on your capture to 200ms to get some more detail. I'm betting the 'drop out' is much more regular than what you're seeing at two seconds.
I've been wrong before, but I'm fairly sure the drop out you're seeing is part of the TAC module circuit monitoring strategy. Check out PIP3461 attached below. It's not for this YMM, but it gives you an idea of how the TAC module will manipulate signals for test purposes.
Would it be possible for you to post the data from the TAC scan data list while the P2135 is current?
ill be looking at an izuzu npr this weekend ill get captures for you to compare to.
you may want to check for contact points on the harness and see if there are damaged wires at those points given the cab has to be tilted to get to the motor it might not be acting up with the cab lifted while your doing your tests.
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