Possible causes

– Obstructions in the airflow of the radiator or transmission cooler
– Kinked or damaged transmission fluid lines
– Damage to the transmission cooler

Tech notes

Check transmission fluid level and condition and replaced fluid if necessary.

Symptoms

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

P0634 GMC Description

The control solenoid (w/body and TCM) valve assembly has a built-in TCM temperature sensor to detect possible overtemperature conditions of the TCM. This fault indicates the TCM is in an overtemperature condition and the TCM has shut down to protect from possible heat damage to the TCM. TCM will remain off until the over temperature condition no longer exists.