LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Jaguar >> 2000 >> XJ8 Base >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Trouble Code Identification >> DTC P0121: Throttle Position Sensor Circuit Range/Performance >> Diagnostic Test Procedure
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Diagnostic Test Procedure

  1. Disconnect negative battery cable. Disconnect the ECM connector EM81. Disconnect the TPS connector. Measure resistance between ECM harness connector EM81 terminal No. 10 and TPS harness connector terminal No. 3. Is resistance greater than 5 ohms? If yes, repair high resistance between ECM harness connector EM81 terminal No. 10 and TPS harness connector terminal No. 3. If no, go to next step.
  2. Reconnect negative battery cable. Turn ignition on. Measure voltage between TPS harness connector terminal No. 3 and ground. Is voltage greater than 5 volts? If yes, repair short to high voltage. If no, go to next step.
  3. Turn ignition off. Measure resistance between TPS harness connector terminal No. 3 and ground. Is resistance less than 10,000 ohms? If yes, repair short to ground. If no, install a new TPS.
scientia non olet · About LEMON Manuals