Diagnostic Aids

Perform this test only when directed by QUICK TEST. This test is intended to diagnose the following:

TP sensor.
Wiring harness circuits (PWR GND, SIG RTN, TP, VPWR and VREF).
Powertrain Control Module (PCM).

Normal range of throttle angle measurement for TP sensor is 0-85 degrees. To pass QUICK TEST procedure, range of throttle rotation (in degrees) must be within 3 percent of specification.

To prevent replacement of good components, be aware, the following non-EEC related areas may be at fault:

Idle speed.
Binding throttle shaft or linkage.
TP sensor not seated.

1) Continuous Memory Code P1121 This code indicates TP signal is inconsistent with MAF sensor signal. Possible causes for this fault are as follows:

TP sensor not seated correctly.
Faulty TP sensor.
Air leak between MAF sensor and throttle body.

If engine will start, go to next step. If engine is a no-start, check for cracks or openings in air induction system between MAF sensor and throttle body. If air induction system is okay, diagnose no-start condition and repair.

2) Check Operation Of TP Sensor Start engine and allow to idle. Access TP PID on scan tool. While observing TP PID, slowly move throttle through range from closed position to wide open throttle. If TP PID indicates any sudden drops to below 0.53 volt, or increases to more than 1.27 volts, replace TP sensor and repeat QUICK TEST. If TP PID increase and decrease is gradual and smooth, and within 0.53-1.27 volt range, go to next step.

3) Check Operation Of TP Sensor While Driving Vehicle Connect scan tool to DLC. Drive vehicle while accessing TP PID and LOAD PID. If TP PID is 2.44 volts or less and LOAD PID is more than 25 percent, go to next step. If TP PID is more than 2.44 volts and LOAD PID is less than 25 percent, check for cracks or openings in air induction system between MAF sensor and throttle body. If air induction system is okay, replace TP sensor.

4) Check TP Sensor Low With Engine Under Load Start engine and allow to idle. Access TP PID and LOAD PID on scan tool. If TP PID is 0.24 volt or more and LOAD PID is less than 60 percent, fault is intermittent and cannot be located at this time. Testing is complete. If TP PID is less than 0.24 volt and LOAD PID is 60 percent or more, clear PCM memory. Perform test drive utilizing all phases of vehicle operation. Perform QUICK TEST. If DTC P1121 is still present, replace MAF sensor.