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Home >> Saturn >> 2002 >> L100 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P1640: Control Module Output Circuit >> Diagnostic Procedure
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Diagnostic Procedure

NOTE: If DTC P0753, P0758 or P1860 is also set, diagnose that DTC first. P1640 will also set if a 1-2 or 2-3 shift solenoid or TCC solenoid fault exists. See appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS.
  1. Turn ignition ON, engine OFF. Using scan tool, review DTC P1640 failure record. Observe A/C RELAY CKT OPEN SHORT TO GND. If scan tool reads YES, see DTC P1640: A/C RELAY CONTROL CIRCUIT LOW VOLTAGE  . If scan tool reads NO, go to next step.
  2. Using scan tool, observe A/C RELAY CKT SHORT TO VOLTS. If scan tool reads YES, see DTC P1640: A/C RELAY CONTROL CIRCUIT HIGH VOLTAGE  . If scan tool reads NO, go to next step.
  3. Using scan tool, observe MODULE DRIVER OVERVOLT and MODULE DRIVER OVERTEMP. If scan tool reads YES for either, record all PCM DTCs and reprogram PCM. See PCM REPROGRAMMING  under PROGRAMMING. If this fault returns, replace and reprogram the PCM. If scan tool reads NO for both, see DIAGNOSTIC AIDS  .
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