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Home >> Jaguar >> 1996 >> XJS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self Diagnostics >> Self-Diagnostic Tests >> DTC P1509: Idle Speed Control (ISC) Circuit
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DTC P1509: Idle Speed Control (ISC) Circuit

NOTE: After each repair, clear DTCs. See CLEARING CODES/PCM RESET PROCEDURE  under SELF-DIAGNOSTIC SYSTEM. Turn ignition off and then on. Read DTCs to verify repair is complete. For DLC and PCM connector terminal identification, see CONNECTOR IDENTIFICATION  . For wiring diagrams, see WIRING DIAGRAMS  .
  1. Using scan tool, read DTCs. If DTC P1509 is present, turn ignition off. Ensure Idle Air Control (IAC) valve harness and connectors are not damaged and connections are okay. Repair as necessary. If harness and connectors are okay, go to next step.
  2. Disconnect IAC valve harness connector. Check for continuity between IAC connector terminal No. 1 (Orange/Yellow wire) and terminals No. 2 (Orange/Black wire), No. 3 (Orange/Red wire) and No. 4 (Orange/Green wire). Also check for continuity between IAC connector terminal No. 2 (Orange/Black wire) and terminals No. 3 (Orange/Red wire), No. 2 (Orange/Black wire) and No. 4 (Orange/Green wire). Repair wiring as necessary. If wiring is okay, go to next step.
  3. Check for continuity between IAC terminals No. 1 and 2, 1 and 3, 1 and 4, 2 and 3, 2 and 4 and terminals No. 3 and 4. If continuity is present, go to next step. If continuity is not present, replace IAC valve.
  4. Clear DTCs. Turn ignition off and then on. Read DTCs. If DTC P1509 is not present, repair is complete. If DTC P1509 is present, replace PCM.
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