P0218
Transmission Fluid Over Temperature
The TCM/PCM detected that automatic transmission fluid temperature exceeded the safe operating threshold. Continued operation accelerates wear on clutches and friction surfaces; many vehicles will engage a fail-safe mode and limit gear selection.
- Check engine light: Yes
- Emissions related: No
- Repair difficulty: medium
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
Common causes
Ordered by how often each turns out to be the cause.
- Low or degraded transmission fluidCommon
- Transmission cooler blocked or restrictedPossible
- Sustained heavy load or towingPossible
Parts involved
- Transmission Fluid
- Transmission Cooler
- Transmission Temperature Sensor
P0218 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.