DTC P1283: IDLE SELECT SIGNAL INVALID

Monitor & Set Conditions

Idle select switch signal is monitored when ignition is on. DTC may be stored if Fuel Pump Control Module (FPCM) detects a false low idle select signal from ECM. FPCM is incorporated into fuel injection pump and may also be referred to as the fuel injection pump when referencing to wiring diagram.

Possible Causes

• Low Idle Select Circuit Open
• Low Idle Select Circuit Shorted To Ground
• ECM - Low Idle Select Circuit
• Low Idle Select Circuit Short To Voltage
• ECM
• Low Idle Select Circuit Shorted To Ground In ECM

Testing

1. Turn ignition off. Disconnect Fuel Pump Control Module (FPCM) harness connector. FPCM connector is located on end of fuel injection pump. Disconnect ECM harness connector. ECM is located on driver's side of engine, just in front of fuel transfer pump and contains a 50-pin connector. Check for poor connection/terminal contact at ECM harness connector. Repair as necessary. Using DVOM, measure resistance of Violet/Orange wire between terminal No. 4 on FPCM harness connector and terminal No. 34 on ECM harness connector. If resistance is 5 ohms or less, go to next step. If resistance is greater than 5 ohms, repair open in Violet/Orange wire between FPCM and ECM.

2. Ensure ignition is off. Ensure FPCM connector and ECM connector are still disconnected. Using DVOM, measure resistance between ground and terminal No. 34 (Violet/Orange wire) at ECM harness connector. If resistance is greater than 5 ohms, go to next step. If resistance is 5 ohms or less, repair short to ground in Violet/Orange wire between FPCM and ECM.

3. Ensure ignition is off and FPCM harness connector is still disconnected. Reinstall ECM harness connector. Turn ignition on with engine off. Using DVOM, measure voltage between ground and terminal No. 4 (Violet/Orange wire) on FPCM harness connector. If voltage is 6 volts or less, go to next step. If voltage is greater than 6 volts, replace and program ECM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. ECM is located on driver's side of engine, just in front of fuel transfer pump and contains a 50-pin connector.

4. Turn ignition off. Ensure FPCM harness connector is still disconnected. Disconnect ECM harness connector. Turn ignition on with engine off. Using DVOM, measure voltage between ground and terminal No. 4 (Violet/Orange wire) on FPCM harness connector. If voltage is 6 volts or less, go to next step. If voltage is greater than 6 volts, repair short to voltage on Violet/Orange wire between FPCM and ECM.

5. Turn ignition off. Ensure FPCM harness connector is still disconnected. Reconnect ECM harness connector. Connect DVOM between ground and terminal No. 4 (Violet/Orange wire) on FPCM harness connector. If resistance is 5 ohms or less, test is complete. If resistance is greater than 5 ohms, replace and program ECM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article.