P0509

SYMPTOM
P0509-IDLE AIR CONTROL VALVE SENSE CIRCUIT HIGH

WHEN MONITORED
Engine running. Battery voltage greater than 10 volts. IAC motor operating.

SET CONDITION
The PCM senses a short to ground or battery voltage on any of the Linear Idle Air Control (LIAC) control circuits for 2.75 seconds while the IAC motor is active. One Trip Fault. Three good trips to turn off the
MIL.

POSSIBLE CAUSES
- (K961) IAC RETURN CIRCUIT SHORTED TO BATTERY VOLTAGE
- (K61) IAC CONTROL CIRCUIT SHORTED TO BATTERY VOLTAGE
- (K61) IAC CONTROL CIRCUIT SHORTED TO (K961) IAC RETURN CIRCUIT
- IAC MOTOR
- PCM

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Scan Tool Testing and Procedures

DIAGNOSTIC TEST
1. IAC MOTOR OPERATION





Note: If the engine will not idle, maintain an engine speed between 800 and 1500 RPM.

Start the engine.
Allow the engine to idle.
With a scan tool, read the IAC Current.
Is the IAC Current above 999 mA?
Yes>> Go To 2
No>> Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5. Powertrain Verification Test - Ver 5

2. IAC MOTOR





Turn the ignition off.
Disconnect the IAC Motor harness connector.
With the scan tool, monitor the IAC Current.
Ignition on, engine not running.
Does the scan tool display IAC Current at 0 mA?
Yes>> Replace the IAC Motor. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.
No>> Go To 3

3. (K961) IAC SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE





Turn the ignition off.
Disconnect the PCM harness connectors.
Ignition on, engine not running.
Measure the voltage on the (K961) IAC Signal circuit in the IAC Motor harness connector.
Is the voltage above 0.5 of a volt?
Yes>> Repair the short to battery voltage in the (K961) IAC Signal circuit. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.
No>> Go To 4

4. (K61) IAC CONTROL CIRCUIT SHORTED TO BATTERY VOLTAGE





Turn the ignition off.
Measure the voltage on the (K61) IAC Control circuit in the IAC Motor harness connector.
Is the voltage above 0.5 of a volt?
Yes>> Repair the short to battery voltage in the (K61) IAC Control circuit. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.
No>> Go To 5

5. (K61) IAC CONTROL CIRCUIT SHORTED TO (K961) IAC RETURN CIRCUIT





Measure the resistance across the (K961) IAC Signal circuit and the (K61) IAC Control circuit in the IAC Motor harness connector.
Is the resistance below 5.0 ohms?
Yes>> Repair the short between the (K961) IAC Signal circuit and the (K61) IAC Control circuit. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.
No>> Go To 6

6. PCM

Note: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.

Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.
Were there any problems found?
Yes>> Repair as necessary. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.
No>> Replace and program the Powertrain Control Module per Service Information. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.