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Throttle actuator control module (TAC) Position Performance

Throttle by wire, module on pedal and module in throttle body. No distinct module on throttle body to service. The truck goes into “reduced power mode” and resumes normal operation as soon as the code is cleared. Four occurrences in the last 3000 miles; very annoying. Anyone know a fix? Is there new code to address this?

It is a 2003 GMC Sierra, sorry for not stating that.

What is the exact code you are getting? There are communication codes, Pedal Position Module codes, and TAC codes. If we had an idea of the code being set, we could give you a diagnostic tree to use in your trouble shooting. Otherwise, it is part shot gun time and those modules are not cheap!

BTW P1125 looks like an interesting code – any chance that is what you are getting? The trouble shooting tree covers a lot of common ground. One thing you will need is a scan tool capable of reading the module position potentiometers and of watching for pending and set codes in real time.

Hope to help.

Life was good when there was a thing called a throttle cable :slight_smile:

Ahh, the things engineers think of to give us traction control, stability control, and increased fuel economy.

I wrote it down on two instances looking back at the papers, both times I wrote the same thing; manufacture specific code:[Throttle Actuator Control (TAC) module position performance]

I don’t want to influence your diagnosis but my thought was that the pedal position sensor or the throttle position sensor was bad. There doesn’t appear to be a TPS that can be serviced separately from the throttle body. It will surely happen again; I’d hoped it was a common issue. I will drive about with a scan tool and maybe, figure out how to monitor potentiometers. Probably a P1516, but I didn’t write that down. Thanks -mark

Read this-

Thanks for the info; the link to the diagnostic procedure is interesting but a little intimidating; especially since I don’t have the service manual for this truck.

Here’s where I stand; I drove the truck today and it behaved fine. My scan tool was plugged in and it does apparently monitor some of the inputs. I don’t know all the abbreviations, but I watched one parameter (TP); don’t know if this is pedal input or actual throttle position. I found that stopped at a traffic light (foot off accelerator) this number would bounce as much as 3%. No code was set today; Three percent fluctuation at idle, do you think this is normal behavior?