Possible Causes

Malfunction "A" will cause ECM to illuminate MIL and set DTC P0121 when a high voltage from the TPS is sent to ECM under light load driving conditions.

Malfunction "B" will cause ECM to illuminate MIL and set DTC P0121 when a low voltage from the TPS is sent to ECM under heavy load driving conditions. Possible causes of malfunctions "A" and "B" are:

• Poor, loose, corroded or damaged terminal connections.
• TPS circuits open or shorted.
• Faulty fuel injector.
• Faulty Crankshaft Position (CKP) sensor (REF).
• Faulty CKP sensor (POS).
• Faulty MAF sensor.
• Intake air leaks.
• Faulty TPS.