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Home >> Land Rover >> 2001 >> Range Rover HSE >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System & Component Testing >> Idle Control System >> Idle Air Control Valve (IACV)
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Idle Air Control Valve (IACV)

CAUTION: The IACV rotary valve may be damaged if it is forced to move by mechanical means.
NOTE: The ECM sets engine cold start idle speed and default idle speed at 1200 RPM. Although the engine idle speed is the same, one condition represents normal engine operation and the other does not.
  1. IACV has a 3-pin connector and is located on the side of the intake air duct. IACV is used to maintain good quality idle speed under all operating conditions. IACV has 2 coils that use opposing PWM signals to control the open or closed positions of a rotary valve. IACV OPEN PWM signal is sent from ECM 52-pin connector C0636 terminal No. 42 (Red/Green wire). IACV CLOSE PWM signal is sent from ECM 52-pin connector C0636 terminal No. 43 (Blue/Gray wire). If one of the PWM signals fails, the ECM closes down the remaining signal causing the IACV to revert to a default position.
  2. Check for an intake air system air leak. Check for blocked, restricted or crimped IACV actuator port or hoses.
  3. Turn ignition off. Disconnect IACV 3-pin connector. Turn ignition on. Measure voltage between ground and IACV 3-pin connector terminal No. 2 (Brown/Orange wire). If battery voltage is present, go to step  5. On Discovery Series II, if battery voltage is not present, check fuse No. 2 (15-amp) located in engine compartment fuse/relay box. On Range Rover, if battery voltage is not present, check fuse No. 37 (30-amp). On all models, if fuse is okay, go to next step. If fuse is not okay, replace fuse and recheck component operation.
  4. Turn ignition off. Check for continuity in Brown/Orange wire between fuse and IACV 3-pin connector terminal No. 2. If continuity does not exist, repair Brown/Orange wire as necessary. If continuity exists, check main relay operation and circuit between fuse and ignition switch. Perform repairs as necessary.
  5. Turn ignition off. Check for continuity in Red/Green wire between IACV 3-pin connector terminal No. 1 and ECM 52-pin connector C0636 terminal No. 43. If continuity exists, go to next step. If continuity does not exist, repair Red/Green wire as necessary.
  6. Turn ignition off. Check for continuity in Blue/Gray wire between IACV 3-pin connector terminal No. 3 and ECM 52-pin connector C0636 terminal No. 42. If continuity exists, go to next step. If continuity does not exist, repair Blue/Gray wire as necessary.
  7. Turn ignition off. Using a fused jumper wire, connect battery voltage to IACV terminal No. 2 (Brown/Orange wire). Using another jumper wire, alternately ground IACV terminals No. 1 (Red/Green wire) and No. 3 (Blue/Gray wire). Replace IACV if IACV actuator operation can not be detected.
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