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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 30 (HVAC SYSTEMS - AUTOMATIC)DIAGNOSTIC TESTSDTC B0490: PASSENGER DOOR MODULE
1999 GMC Forward Control 5.7 R, Automatic

DTC B0490: Passenger Door Module

1999 GMC Forward Control 5.7 R, AutomaticSECTION DTC B0490: Passenger Door Module
WARNING: This page is about a different car, the 2002 Oldsmobile Aurora. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: The numbers below refer to the step numbers of the diagnostic procedure:
  1. 2  - The value given is the normal condition that exists when the switch is in the neutral position.
  2. 3  - Tests for the proper operation of the circuit in the high voltage range.
  3. 4  - Tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to voltage.
  1. Perform diagnostic system check. See DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing system check, go to next step.
  2. Connect scan tool. Turn ignition on. Place passenger-side temperature control switch in Neutral position. Using scan tool, observe PASS. HVC SWITCH parameter in DRIVER DOOR MODULE data list. If scan tool indicates PASS. HVC SWITCH parameter is near 143 counts, inspect wiring and connectors for intermittent loose wires and/or poor connections. Repair as necessary. If scan tool indicates PASS. HVC SWITCH parameter is not near 143 counts, go to next step.
  3. Turn OFF the ignition. Disconnect the Right Air Temperature Switch Assembly. Turn ON the ignition, with the engine OFF. With a scan tool, observe the PASS. HVAC SWITCH parameter. Does the scan tool indicate that the PASS. HVAC SWITCH parameter is greater than 250 counts? If so, go to next step. If not go to step  5.
  4. Turn OFF the ignition. Connect a 3-amp fused jumper wire between the right air temperature switch signal circuit (Pink wire) and the low reference circuit (Purple wire) of the right air temperature switch assembly. Turn ON the ignition, with the engine OFF. With a scan tool, observe the PASS. HVAC SWITCH parameter. Does the scan tool indicate that the PASS. HVAC SWITCH parameter is less than 5 counts? If so, go to step  8. If not, go to step  6.
  5. Check the Right Air Temperature Switch signal circuit (Pink wire) of the Right Air Temperature Switch assembly for a short to ground. See WIRING DIAGRAMS . If short to ground is found, repair and go to step  12. If short to ground is not found, go to step  9.
  6. Check the Right Air Temperature Switch signal circuit (Pink wire) of the Right Air Temperature Switch assembly for a short to voltage, a high resistance, or an open. See WIRING DIAGRAMS . If a short to voltage, a high resistance, or an open is found, repair and go to step  12. If not go to next step.
  7. Check the low reference circuit (Purple wire) of the right air temperature switch assembly for high resistance or an open. If high resistance or an open is found, repair and go to step  12. If not, go to step  9.
  8. Inspect for poor connections at the harness connector of the right air temperature switch assembly. See INTERMITTENTS . If poor connections are found, repair and go to step  12. If not go to step  10.
  9. Inspect for poor connections at the harness connector of the Front Passenger Door Module. See INTERMITTENTS . If poor connections are found, repair and go to step  12. If not go to step  11.
  10. Replace the right air temperature switch assembly. See PASSENGER-SIDE TEMPERATURE CONTROL PANEL  under REMOVAL & INSTALLATION. When repairs are complete go to step  12.
  11. Replace the Front Passenger Door Module. Located under passenger door panel. When repairs are complete go to next step.
  12. Use the scan tool in order to clear the DTCs. Operate vehicle, if DTCs reset go to step  2. If not repairs are complete.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.