Mike's Workshop Manuals: Service manuals for every vehicle
Home >> Chevrolet >> 1998 >> Venture Base, Van Passenger Extended >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Tests W/Codes >> Diagnostic Trouble Codes >> DTC P1635 - 5-Volt Reference "A" Circuit >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK , then go to next step.
  2. Inspect PCM engine grounds. Ensure grounds are clean and tight. Repair as necessary. After repairs, go to step 12). If grounds are okay, go to next step.
  3. Check if any other DTCs are set. If any other DTCs are set, diagnose DTCs as necessary. If multiple sensor DTCs are set, check for open or shorts in circuits common to all sensors (5-volt reference and sensor ground circuits). If no other DTCs are set, go to next step.
  4. Turn ignition off. Disconnect PCM connector. Turn ignition on. Using DVOM, check voltage between sensor ground circuit and 5-volt reference "A" circuit terminals at PCM connector. If voltage is greater than 5 volts, go to next step. If voltage is not greater than 5 volts, go to step 9).
  5. Ensure DVOM is still connected between sensor ground circuit and 5-volt reference "A" circuit terminals at PCM connector. Observe DVOM and disconnect EGR valve connector. If voltage is greater than 5 volts, go to next step. If voltage is not greater than 5 volts, go to step 8).
  6. Observe DVOM and disconnect TP sensor connector. Again, observe DVOM and disconnect MAP sensor connector. If voltage changes when one of the sensors is disconnected, locate and repair short to voltage in suspect sensor signal circuit. After repairs, go to step 12). If voltage does not change when sensors are disconnected, go to next step.
  7. Turn ignition off. Disconnect PCM connector. Turn ignition on. Check 5-volt reference "A" circuit for a short to voltage. Repair as necessary. After repairs, go to step 12). If circuit is okay, go to step 11).
  8. Replace EGR valve. After replacing EGR valve, go to step 12).
  9. If voltage is less than 4.5 volts, go to step 10). If voltage is not less than 4.5 volts, go to step 11).
  10. Turn ignition off. Disconnect PCM connector. Check for short to ground in 5-volt reference "A" circuit. Repair as necessary. After repairs, go to step 12). If circuit is okay, go to next step.
  11. Replace PCM. Program replacement PCM using required equipment. After repair is completed, go to next step.
  12. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle within conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info for DTC P1635 until DTC P1635 test runs. If scan tool indicates FAILED THIS IGN, repeat step 2). If scan tool does not indicate FAILED THIS IGN, repair is complete.
scientia non olet · About Mike's Workshop Manuals