LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> GMC >> 2003 >> Jimmy 2D Utility, Part Time, Automatic >> Repair and Diagnosis >> External Pages >> Different car >> Section 49 (Engine Controls Self-Diagnostics) >> Diagnostic Tests >> DTC P1635: 5-Volt Reference A Circuit >> Diagnostic Procedures
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Diagnostic Procedures

WARNING: This page is about a different car, the 2003 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.
  1. Did you perform the Diagnostic System Check-Engine Controls? If yes, go to next step. If no, see DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
  2. Observe the Freeze Frame/Failure Records for this DTC. Turn OFF the ignition for 30 seconds. Turn ignition ON, with engine OFF. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition cycle? If yes, go to next step. If no, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM.
  3. Turn ignition OFF. Disconnect the MAP sensor electrical connector. Turn ignition ON, with engine OFF. Measure voltage between the MAP sensor 5-volt reference circuit and a good ground. Is voltage 4.8-5.2 V? If yes, go to step  5. If no, go to next step.
  4. Is the voltage from the previous step more than the specified value? If yes, go to step  8. If no, go to step  6.
  5. Reconnect MAP sensor. Disconnect Engine Oil Pressure (EOP) sensor. Measure the voltage between the EOP sensor 5-volt reference circuit and a good ground. Is the voltage 4.8-5.2 V? If yes, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM. If no, go to step  9.
  6. Monitor the voltage while disconnecting the EOP sensor. If voltage changes when the sensor is disconnected, replace the EOP sensor. Was a component replaced? Did you complete the replacement? If yes, go to step  12. If no, go to next step.
  7. Turn ignition OFF. Disconnect the PCM. Test the 5-volt reference circuit for a short to ground or any sensor low reference circuit. Did you find and correct the condition? If yes, go to step  12. If no, go to step  11.
  8. Turn ignition OFF. Disconnect PCM. Turn ignition ON, with engine OFF. Test the 5-volt reference circuit for a short to voltage. Did you find and correct the condition? If yes, go to step  12. If no, go to step  11.
  9. Test the MAP sensor signal circuit for a short to voltage. Did you find and correct the condition? If yes, go to step  12. If no, go to step  10.
  10. Replace MAP sensor. See MANIFOLD ABSOLUTE PRESSURE SENSOR under SENSORS in REMOVAL & INSTALLATION - CORVETTE article. Did you complete the replacement? If yes, go to step  12.
  11. Replace PCM. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL & INSTALLATION - CORVETTE article. Did you complete the replacement? If yes, go to next step.
  12. Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running DTC. Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  13. Observe the stored information, Capture Info with a scan tool. Does the scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
scientia non olet · About LEMON Manuals