I took my 01 silveraod in to the dealership today to find what is causing my engine to stumble when you first hit the gas from an idle. We hooked it up to the computer, and it was showing 0's on both the TPS values. Basically, the computer is reading no change in the throttle blade no matter how much the blade actually opens....does that make sense. they hooked up a new TPS sensor and still no change. what could possible be wrong to make the computer not read any input from the TPS?


GregM

 

a broken wire between the computer and the TPS......

 

Yea, what Yelo said. There's either an open in the circuit between the TPS and the PCM, or a problem internally with the PCM. More than likely a wire though.

 

What's the best way to track the problem down? The service tech was showing a TPS actuator in his computer, but we could not find it on my truck. All the techs were totally stumped.


GregM

 

Please tell me you didn't pay a diagnosis charge for that.

 

Well, you need a schematic and a system description that lets you know what wires should have what voltages under certain conditions. Then you basically get a voltmeter and backprobe each wire at the TPS and PCM until you find the one that is not within spec. Once you find the problem wire, try to see if you can find an open, or a short as the case may be.

You say there's a new TPS in there, so that should be good (although you never know). Well, assuming that it is, if all of the wires check out OK, then the problem is with the PCM...so you get a new PCM with a custom tune and leave skid marks 50 feet long!

 

That's EXACTLY what I did the last time I went to the dealership and saw the prices they charge for stuff !!!

 

I did not pay for the diagnostic, they were a cool bunch of guys. I plan on getting a pcmforless tune as soon as I get my headers and tires, but I wanted to get this sorted out first.

Just so i'm not totally a moron here, the cable actuated throttle bodies will show how much the blade is open when you hook it up to the diagnostic computer right?? I know i'm sounding like an idiot here because all this terminology is new to me. The computer was showing no change at all no matter how much the throttle was opened.


GregM

 

well like they say two fixes for the problem if you have an ohm meter you could prolly find out if it is a short or make the dealership fix it and tell em you wont pay for it i have heard plenty of dealershipe caving in to stupid @#%& like that even replacing motors than were blown on nitrous so argue with em and get em to fix it

 

Yea, as you open the throttle, the percentage of throttle angle should change on the scan tool. (by the way, you don't sound like an idiot...you're just in the learning phase, and the fact that you were able to get some diag time on a scan tool for free proves you're not an idiot!)