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Home >> Oldsmobile >> 2001 >> Intrigue GLS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P1639: 5-Volt Reference "B" Circuit >> Diagnostic Procedures
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Diagnostic Procedures

  1. If powertrain diagnostic system check has already been performed, go to next step. If powertrain diagnostic system check has not been performed, go to POWERTRAIN DIAGNOSTIC SYSTEM CHECK  under DIAGNOSTIC SYSTEM CHECKS.
  2. Check PCM and engine grounds. Ensure grounds are clean and tight. See WIRING DIAGRAMS article. If any problems are found, repair as necessary. After repairs, go to step  10. If no problems are found, go to next step.
  3. If any other DTCs are set, repair DTCs as necessary before continuing with this test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no other DTCs are set, go to next step.
  4. Disconnect A/C pressure sensor connector. Sensor is located in discharge hose of A/C compressor. Disconnect FTP sensor connector. FTP sensor is located on top of fuel tank and can be accessed through an inspection panel in trunk. Turn ignition on. Measure voltage between ground and 5-volt reference circuit (Gray wire) at either disconnected sensor harness connector. If voltage is 4.5-5.5 volts, go to next step. If voltage is not 4.5-5.5 volts, go to step  8.
  5. Reconnect one disconnected sensor at a time while measuring voltage between ground and 5-volt reference circuit (Gray wire) at other disconnected sensor harness connector. If sensor being reconnected caused voltage to vary outside 4.5-5.5 volts, go to next step. If sensor being reconnected did not cause voltage to vary outside 4.5-5.5 volts, see DIAGNOSTIC AIDS .
  6. Check for short to power or short to ground on all other circuits connected to affected sensor. See WIRING DIAGRAMS article. Repair wiring as necessary. After repairs, reconnect sensor and repeat previous step. If wiring is okay, go to next step.
  7. Replace affected sensor. After repairs, go to step  10.
  8. Turn ignition off. Disconnect PCM harness connector. PCM is located in left front corner of engine compartment, inside air filter housing. Turn ignition on. Check 5-reference circuit (Gray wire) for short to ground and short to power. Repair wiring as necessary. After repairs, go to step  10. If wiring is okay, go to next step.
  9. Replace PCM. Program replacement PCM. See PROGRAMMING . After repairs, go to next step.
  10. Turn ignition off. Reconnect all disconnected connectors. Turn ignition on. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within conditions for running the DTC as specified in code enable criteria. If DTC runs and passes, go to next step. If DTC resets, go to step  2.
  11. Using scan tool, check for any other DTCs that are set. If no other DTCs are set, test is complete. If any other DTCs are set, repair DTCs as necessary. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
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