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DTC P1224: Electronic Throttle Control Position Error

  1. Check fuses F9 and F14 in engine management fuse box. Replace, if necessary and retest system. If fuses are okay, go to next step.
  2. Remove throttle motor power relay located in engine compartment, in control module enclosure. Turn ignition on. Measure voltage between main relay harness connector terminal No. 3 (Brown/Green wire) and ground point G121 (on XJ Series), or G105 (on XK8). See WIRING DIAGRAMS article. See Figure. If battery voltage exists, go to next step. If battery voltage does not exist, go to step  9.
  3. Turn ignition off. Disconnect 2-pin throttle motor harness connector at throttle assembly. Measure resistance between throttle motor harness connector terminals. If resistance is .54-1.04 ohms, go to next step. If resistance is not .54-1.04 ohms, replace electronic throttle assembly and retest system.
  4. Measure resistance between throttle motor terminal No. 1 and throttle body. If resistance is more than 10 megohms, go to next step. If resistance is 10 megohms or less, replace electronic throttle assembly and retest system.
  5. Disconnect ECM harness connectors EM13 and EM14. Turn ignition on. Measure voltage between ECM harness connector EM13 terminal No. 14 (Green/Red wire) and ECM harness connector EM14 terminal No. 8 (Black wire). See Figure. If battery voltage exists, replace relay and retest system. If battery voltage does not exist, go to next step.
  6. Turn ignition off. Check continuity of Green/Red wire between ECM harness connector EM13 terminal No. 14 and throttle motor power relay harness connector terminal No. 2. See Figure. If continuity exists, go to next step. If continuity does not exist, repair open in Green/Red wire and retest system.
  7. Turn ignition on. Measure voltage between ECM harness connector EM14 terminal No. 8 (Black wire) and throttle motor power relay harness connector terminal No. 1 (White/Purple wire). If battery voltage exists, go to next step. If battery voltage does not exist, repair open or short in power supply circuit and retest system. See WIRING DIAGRAMS article.
  8. Turn ignition off. Check continuity of Green/Yellow wire between ECM harness connector EM14 terminals No. 1 and 2 and throttle motor power relay harness connector terminal No. 5. If continuity exists, go to next step. If continuity does not exist, repair open in Green/Yellow wire and retest system.
  9. Disconnect engine management fuse box harness connector EM19. Check continuity of Brown/Green wire between engine management fuse box harness connector EM19 terminal No. 2 and throttle motor power relay harness connector terminal No. 3. See Figure and Fig 1 . If continuity exists, go to next step. If continuity does not exist, repair open in Brown/Green wire and retest system.
  10. Disconnect 2-pin throttle motor harness connector at throttle assembly. Disconnect ECM harness connector EM14. Check continuity of Red wire between ECM harness connector EM14 terminals No. 5 and 6 and throttle motor harness connector terminal No. 1. See Figure. If continuity exists, go to next step. If continuity does not exist, repair open in Red wire and retest system.
  11. Check continuity of Green wire between ECM harness connector EM14 terminals No. 11 and 12 and throttle motor harness connector terminal No. 2. If continuity exists, go to next step. If continuity does not exist, repair open in Green wire and retest system.
  12. Disconnect ECM harness connectors EM10 and EM15. Measure resistance between ECM harness connector EM14 terminals No. 7 and 8 (Black wires) and ground point G121 (on XJ Series), or G105 (on XK8). See WIRING DIAGRAMS article. If continuity exists, go to next step. If continuity does not exist, repair open ground circuit and retest system.
  13. Remove 10-amp fuse F14 from engine management fuse box. Ensure ECM harness connectors EM12, EM13, EM14 and EM15 are disconnected. Turn ignition on. Measure voltage between ECM harness connector terminal EM13 terminal No. 14 (Green/Red wire) and ECM harness connector terminal EM14 terminal No. 8 (Black wire). See Figure. If voltage is zero volts, go to next step. If voltage is more than zero volts, repair short to voltage and retest system.
  14. Turn ignition off. Remove 30-amp fuse F9 from engine management fuse box. Turn ignition on. Measure voltage between ECM harness connector EM14 terminal No. 8 (Black wire) and throttle motor power relay harness connector terminal No. 3 (Brown/green wire). If voltage zero volts, go to next step. If voltage is more than zero volts, repair short to voltage and retest system.
  15. Measure voltage between ECM harness connector EM14 terminal No. 8 (Black wire) and throttle motor power relay harness connector terminal No. 5 (Green/Yellow wire). If voltage is zero volts, go to next step. If voltage is more than zero volts, repair short to voltage and retest system.
  16. Reconnect throttle motor harness connector. Measure voltage between ECM harness connector EM14 terminals No. 5 (Red wire) and No. 8 (Black wire), then measure voltage between ECM harness connector EM14 terminals No. 6 (Red wire) and No. 8 (Black wire). If voltage is zero volts, go to next step. If voltage is more than zero volts, repair short to voltage and retest system.
  17. Turn ignition off. Disconnect ECM harness connector EM13. Measure resistance between ECM harness connector EM13 terminal No. 14 (Green/Red wire) and ECM harness connector EM14 terminal No. 1 (Green/Yellow wire), then measure resistance between ECM harness connector EM13 terminal No. 14 (Green/Red wire) and ECM harness connector EM14 terminal No. 2 (Green/Yellow wire). If resistance is more than 10 megohms, go to next step. If resistance is 10 megohms or less, repair short circuit and retest system.
  18. Measure resistance between ECM harness connector EM14 terminals No. 5 (Red wire) and No. 11 (Green wire), No. 5 (Red wire) and No. 12 (Green wire), No. 6 (Red wire) and No. 11 (Green wire), and No. 6 (Red wire) and No. 12 (Green wire). If resistance is more than 10 megohms, system is okay. If resistance is 10 megohms or less, repair short circuit and retest system.
Fig 1: Identifying Engine Management Fuse Box Harness Connector Terminals
G98J12657Courtesy of JAGUAR CARS, INC.
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