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.
Circuit Description
PCM contains an Output Driver Module (ODM) which is used to control up to 7 outputs. ODM controls these components individually by completing the ground circuit when PCM commands them on. ODM is used by the cooling fan control module, EVAP vent solenoid, EVAP purge solenoid, TCC solenoid and A/C relay.
Each circuit controlled by the ODM has a feedback circuit. PCM can compare expected voltage and actual voltage on its feedback. DTC will not set until PCM command the output on (grounded), because that is when the expected voltage does not match the feedback voltage (based on commanded state of output).
Use scan tool to command each outputs on and off to help find an intermittent condition. Set scan tool to Review Failure Record for DTC P1640. Observe scan tool display. If feedback indicates YES in affected circuit, diagnose using appropriate diagnostic procedure step or DTC test. See OUTPUT DRIVER SCAN TOOL PARAMETERS .
| Affected Circuit (1) | Perform Step No. Or DTC Test | ||
|---|---|---|---|
| A/C Relay Circuit Open/Short To Ground | 2 | ||
| A/C Relay Circuit Short To Voltage | 7 | ||
| EVAP Vent Circuit Open/Short to Ground | 14 | ||
| EVAP Vent Circuit Short To Voltage | 18 | ||
| EVAP Purge Circuit Open/Short To Ground | 20 | ||
| EVAP Purge Circuit Short To Voltage | 22 | ||
| Cooling Fan No. 1 Relay Circuit Open/Short To Ground | P0480 | ||
| Cooling Fan No. 1 Relay Circuit Short To Voltage | P0480 | ||
| Cooling Fan No. 2 Relay Circuit Open/Short To Ground | P0481 | ||
| Cooling Fan No. 2 Relay Circuit Short To Voltage | P0481 | ||
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NO RELATED
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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.