DTC P0121: THROTTLE POSITION SENSOR "A" PERFORMANCE Jaguar XJR II

1. Disconnect 5-pin pedal position and mechanical guard sensor and 4-pin TP sensor harness connectors from throttle assembly. Turn ignition on. Measure voltage between TP sensor harness connector terminals No. 1 (Black/Green wire) and No. 4 (Blue/White wire). (Scheme 6) If voltage is not 4.75-5.25 volts, go to next step. If voltage is 4.75-5.25 volts, system is okay.
2. Turn ignition off. Disconnect ECM harness connectors EM10 and EM11. Disconnect Engine Coolant Temperature (ECT) sensor harness connector, located on coolant pipe, near thermostat housing. Check continuity of Black/Green wire between TP sensor harness connector terminal No. 1, ECM harness connector EM10 terminal No. 20 and ECM harness connector EM11 terminal No. 12. see scheme 3 If continuity exists, go to next step. If continuity does not exist, repair open in Black/Green wire.
3. Check continuity of Blue/White wire between TP sensor harness connector terminal No. 4, ECM harness connector EM10 terminal No. 21 and ECM harness connector EM11 terminal No. 8. If continuity exists, go to next step. If continuity does not exist, repair open in Blue/White wire.
4. Ensure only ECM harness connector EM11 is disconnected. Turn ignition on. Measure voltage between ECM harness connector EM11 terminals No. 8 (Blue/White wire) and No. 12 (Black/Green wire). If voltage is 4.75-5.25 volts, system is okay. If voltage is not 4.75-5.25 volts, repair open circuit and retest system. See WIRING DIAGRAMS article.

Scheme 6