Possible causes

– Low transmission fluid level
– Dirty or contaminated fluid
– Internal transmission failure

When is the code detected?

When the Powertrain Control Module (PCM) detects excessive Torque Converter Clutch (TCC) slip when the TCC should be engage, then the trouble code P0894 is set.

P0894 GMC Description

The Powertrain Control Module (PCM) monitors the difference between engine speed and transmission output speed. In D3 drive range with Torque Converter Clutch (TCC) engaged, the engine speed should closely match the transmission output speed. In D4 drive range, with the TCC engaged, the TCC slip speed should be -20 to +50 RPM.

GMC Technical Service Bulletins for P0894 code