Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
2002 Saturn L100FACTORY OEM SERVICE PROCEDURE
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.
- 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.
- 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.
- 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 .
Factory Service Tools
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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.