2001 Chevrolet Tahoe Engine performance

  • 5.3L
  • V8
  • 4WD
I'm getting p0122 code even after replacing the tps and clearing the computer
Monday, July 27th, 2015 AT 11:38 AM

1 Reply

  • 33,797 POSTS
Diagnostic fault codes never say to replace parts or that they're bad. They only indicate the circuit or system that needs further diagnosis, or the unacceptable operating condition. In this case, the throttle position sensor is a very low-failure item. Your mechanic starts the diagnosis by taking a couple of voltage readings at the sensor, then comparing the signal voltage to that shown on the scanner. This fault code can be set by a break in the 5.0 volt feed circuit to the sensor, either a cut wire or a stretched or corroded terminal in the connector. If you find the signal voltage to be correct, the cause of the fault code is an intermittent problem that is not currently acting up. You can usually find them by watching the voltage shown on the scanner while you wiggle on the wiring harness.

If you don't have a scanner, you're limited to a voltmeter, but that should be sufficient to diagnose the cause of the fault code. The voltage readings are only valid when the sensor is plugged in so you'll have to back-probe through the rubber seals around each wire. On one of them you must find 5.0 volts. That's the voltage feed circuit. The ground wire will have very close to 0.2 volts. Both of those have to be correct for the signal wire to be correct. You should find close to 0.5 volts at idle and 4.5 volts at wide-open-throttle. These values are approximate and for explanation purposes. In actual practice you might find 0.78 and 4.2 volts, for example. The important point is the signal voltage must never drop to 0.0 volts or rise to 5.0 volts. Those are the voltages that trigger fault codes.
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Monday, July 27th, 2015 AT 5:08 PM

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