DTC P1488: AUXILIARY 5 VOLT OUTPUT TOO LOW

Monitor & Set Conditions

Auxiliary 5-volt output circuit is monitored with ignition on engine off, and with engine running. DTC may set if voltage on 5-volt sensor supply circuit is less than 4.3 volts for 5 seconds.

Possible Causes

• Manifold Absolute Pressure (MAP) Sensor
• Camshaft Position (CMP) Sensor
• Engine Oil Pressure Sensor
• Water In Fuel Sensor
• 5-volt Supply Circuit Shorted To Ground
• 5-volt Supply Circuit Open
• Broken, Bent Or Pushed Out Terminals
• ECM

Testing

1. Turn ignition on with engine off. Using DRBIII(R) scan tool, check for DTCs. If Good Trip Counter for DTC P1488 is displayed and equal to zero, go to next step. If Good Trip Counter for DTC P1488 is displayed and not equal to zero, go to step 8 .

2. Turn ignition off. Disconnect MAP sensor harness connector. MAP sensor is located on driver's side rear corner of cylinder head. Check for poor connection/terminal contact at MAP sensor harness connector. Repair as necessary. Turn ignition on with engine off. Using DVOM, measure voltage between ground and terminal No. 1 (Orange wire) on MAP sensor harness connector. If voltage is 4.5 volts or less, go to next step. If voltage is greater than 4.5 volts, replace MAP sensor. See appropriate REMOVAL, OVERHAUL & INSTALLATION article.

3. Turn ignition off. Ensure MAP sensor harness connector is still disconnected. Disconnect CMP sensor harness connector. CMP sensor is located on rear of timing gear cover, directly below bottom of fuel injection pump. Check for poor connection/terminal contact at CMP sensor harness connector. Repair as necessary. Turn ignition on with engine off. Using DVOM, measure voltage between ground and terminal No. 1 (Orange wire) on MAP sensor harness connector. If voltage is 4.5 volts or less, go to next step. If voltage is greater than 4.5 volts, replace CMP sensor. See appropriate REMOVAL, OVERHAUL & INSTALLATION article.

4. Turn ignition off. Ensure MAP sensor harness connector and CMP sensor harness connector are still disconnected. Disconnect engine oil pressure sensor harness connector. Engine oil pressure sensor is located on driver's side of cylinder block, just behind Engine Control Module (ECM) and contains 3-pin connector. Engine oil pressure sensor may also be referred to as oil pressure sensor. Check for poor connection/terminal contact at oil pressure sensor harness connector. Repair as necessary. Turn ignition on with engine off. Using DVOM, measure voltage between ground and terminal No. 1 (Orange wire) on MAP sensor harness connector. If voltage is 4.5 volts or less, go to next step. If voltage is greater than 4.5 volts, replace engine oil pressure sensor. See appropriate REMOVAL, OVERHAUL & INSTALLATION article.

5. Turn ignition off. Ensure MAP sensor harness connector, CMP harness connector and oil pressure sensor harness connector are still disconnected. Disconnect Water In Fuel (WIF) sensor harness connector. WIF sensor is located at bottom of fuel filter/water separator on driver's side of engine, just behind fuel injection pump. Turn ignition on with engine off. Using DVOM, measure voltage between ground and terminal No. 1 (Orange wire) on MAP sensor harness connector. If voltage is 4.5 volts or less, go to next step. If voltage is greater than 4.5 volts, replace WIF sensor. See appropriate REMOVAL, OVERHAUL & INSTALLATION article.

6. Turn ignition off. 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. Using DVOM, measure resistance between ground and terminal No. 10 (Orange wire) on ECM harness connector. If resistance is 5 ohms or greater, go to next step. If resistance is less than 5 ohms, repair short to ground in Orange wire between ECM, MAP sensor, engine oil pressure sensor, WIF sensor and CMP sensor.

7. Ensure ECM harness connector and MAP sensor harness connector are still disconnected. Using DVOM, measure resistance of Orange wire between terminal No. 1 on MAP sensor harness connector and terminal No. 10 on ECM harness connector. If resistance is less than 5 ohms, replace and program ECM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. If resistance is 5 ohms or greater, repair open in Orange wire between MAP sensor and ECM.

8. Problem is intermittent. Inspect MAP sensor harness connector and ECM harness connector for corroded, pushed out or damaged terminals. Inspect wiring harness and connectors between MAP sensor and ECM for chafed, pierced or partially broken wires. If terminals are not corroded, pushed out or damaged and wiring is okay, check for technical service bulletins that may apply. If terminals are corroded, pushed out or damaged, or wiring is damaged, repair as necessary.