Possible causes

– Reprogram TCM and recheck code
– Replace Transmission Control Module (TCM) Sensor/body assembly one piece

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)

P1686 PONTIAC Description

The Transmission Control Module (TCM) power up the temperature sensor is located inside of the control solenoid (w/body and TCM) valve assembly and has no serviceable parts. The TCM power up temperature sensor provides the temperature pof the TCM at TCM power up. This temperature readings is used in various shifting and diagnostic routines in the TCM software. This fault is handled inside the TCM and no external circuit are involved.