Possible causes

– Low transmission fluid level
– Transmission cooling system concerns

When is the code detected?

When the Powertrain Control Module (PCM) detects a high transmission fluid temperature (TFT) for a long period of time, then code P0218 will set.

Symptoms

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

P0218 GMC Description

The flow of transmission fluid starts in the bottom pan and is drawn through the filter, control valve body assembly, transmission case and into the oil pump assembly. The oil pump assembly pressurizes the fluid and directs it to the pressure regulator valve where it becomes the main supply of fluid to the various components and hydraulic circuits in the transmission. Hot fluid exiting the torque converter flows through the converter clutch apply valve and into the transmission cooler lines to the oil cooler located in the vehicle radiator (and auxiliary cooler if equipped). From the cooler, fluid returns to cool and lubricate the front of the transmission. In forward drive ranges, D4 fluid from the manual valve is routed through an orificed cup plug in the rear of the transmission case to feed the rear lube fluid circuit.

GMC Technical Service Bulletins for P0218 code