Start Here - Code Will Set If

Diagnostic Chart:

The PCM contains an output driver module (ODM) which controls four circuits: A/C relay, 1-2 shift solenoid, 2-3 shift solenoid and TCC solenoid. The 0DM controls each of these circuits independently by controlling the circuit ground. The 0DM monitors the voltage level at each of the four circuits into the PCM when the device is being commanded On or Off. When the device is commanded Off (circuit not grounded), the voltage level at the PCM should be high (ignition voltage). When the device is commanded On (circuit grounded), the voltage level at the PCM should be low. Each of the four drivers in the 0DM contains a feedback circuit used to determine if a particular circuit failed, which can be read on the Scan tool. DTC P1640 sets when any one of the four feedback voltages is low when that device is turned Off or when any one of the four feedback voltages is high when that device is turned On when the engine is running.

DTC PARAMETERS
DTC P1640 will set if A/C relay, 1-2 shift solenoid, 2-3 shift solenoid or TCC solenoid feedback voltage is less than 4.0 volts when that device is commanded Off when:
^ Condition exists for longer than 6 seconds
^ Engine is running

OR

A/C relay, 1-2 shift solenoid, 2-3 shift solenoid or TCC solenoid feedback voltage is greater than 3.5 volts when that device is commanded On when:
^ Condition exists for longer than 6 seconds
^ Engine is running

DTC P1640 diagnostic runs continuously with engine running.

P1640 is a type C DTC.

DIAGNOSTIC AIDS

IMPORTANT: 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.

To locate an intermittent problem, use Scan to command each of the four solenoids tied to the 0DM circuit On and Off independently while monitoring:
A/C RELAY CKT OPEN SHORT TO GND
A/C RELAY CKT SHORT TO VOLTS
TCC DUTY CYCLE OPEN SHORT TO GND
TCC DUTY CYCLE SHORT TO VOLTS
MODULE DRIVER OVERVOLT
MODULE DRIVER OVERTEMP

If IGN 3 fuse is open, A/C RELAY CKT OPEN SHORT TO GND, EVAP VENT CKT OPEN SHORT TO GND and EVAP PURGE CKT OPEN SHORT TO GND parameters on Scan tool will read YES.