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DTC P0508: Idle Control System Circuit Low Input

  1. Perform basic diagnostic procedure. See BASIC DIAGNOSTIC PROCEDURE  . Turn ignition on. Using a DVOM connected to ground, backprobe ECM connector B136 (24-pin connector) terminal No. 10. See Figure . If voltage is more than 3 volts, repair poor terminal contact in ECM connector. If voltage is not more than 3 volts, go to next step.
  2. Turn ignition off. Disconnect IAC solenoid valve connector. Turn ignition on. Using a DVOM connected to ground, measure voltage at IAC solenoid valve connector terminal No. 2. See Figure . If voltage is more than 10 volts, go to next step. If voltage is not more than 10 volts, locate and repair open circuit in wiring and check for poor terminal contact in connectors between main relay and IAC solenoid valve.
  3. Turn ignition off. Disconnect ECM connector B136 (24-pin connector). Measure resistance between ECM connector B136 (24-pin connector) terminal No. 10 and IAC solenoid valve connector terminal No. 1. If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and IAC solenoid valve.
  4. Measure resistance between ECM connector B136 (24-pin connector) terminal No. 10 and chassis ground. If resistance is less than 10 ohms, locate and repair short to ground in wiring between ECM and IAC solenoid valve. If resistance is not less than 10 ohms, go to next step.
  5. Measure resistance between IAC solenoid valve connector terminal No. 3 and engine ground. If resistance is less than 5 ohms, go to next step. If resistance is not less than 5 ohms, locate and repair open circuit in wiring between IAC solenoid valve and engine ground point.
  6. Check for poor contact in ECM connector B136 (24-pin connector) and IAC solenoid valve connector. Repair as necessary. If connectors are okay, replace IAC solenoid valve. Clear memory and perform verification procedure. CLEARING DIAGNOSTIC TROUBLE CODES  and VERIFICATION PROCEDURE  .
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