P0218

What it means

P0218 is the generic code for a transmission fluid over temperature condition. The transmission control unit has seen the fluid temperature reported by the transmission fluid temperature sensor rise above its calibrated upper limit, and it has set the fault to protect the gearbox. The exact threshold and the way the unit responds vary by manufacturer, model and gearbox type.

Symptoms

• Transmission warning light or overheating message on the dash
• Gearbox going into limp mode or a protective shift pattern
• Harsh, delayed or slipping gear changes
• Torque converter lock-up being inhibited or the engine feeling flat
• Burnt smell from the transmission fluid or a hot gearbox casing
• Poor fuel economy or the engine revving higher than normal

Possible causes

• Low, degraded or burnt transmission fluid, or the wrong fluid typelikely
• Restricted transmission cooler, cooler lines or a blocked external cooler airflow pathlikely
• Heavy towing, sustained high load or aggressive driving beyond the gearbox's cooling capacitylikely
• Internal gearbox wear causing clutch slip and excess heat, or a faulty torque converter clutchpossible
• Faulty cooler thermostat or bypass valve, or a failed cooling pump or flow control valve on models that have onepossible
• Faulty transmission fluid temperature sensor or wiring fault giving a falsely high readingpossible
• Engine cooling system fault feeding heat into the gearbox cooler on models where the cooler uses engine coolantrare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting fluid temperature, vehicle speed, load and engine coolant temperature at the time the fault set.
2. Check for other gearbox, slip-related or engine cooling codes, and look up any manufacturer service bulletins for the model.
3. Check the transmission fluid level and condition using the procedure for that gearbox, looking for a burnt smell, dark colour or debris. Some sealed units need a specific temperature-controlled check.
4. Confirm the fluid specification and service history match what the manufacturer calls for.
5. Inspect the transmission cooler, its lines and the area around it for blockage, damage, kinks or leaks, and check the cooling fans and engine coolant system where the cooler is linked to it.
6. Inspect the sensor wiring and connector for chafing, corrosion, water ingress or fluid contamination.
7. With a scan tool, watch live transmission fluid temperature against engine coolant temperature on a cold start; the readings should be close and rise smoothly. A reading that is implausible suggests a sensor or wiring fault.
8. Check cooler flow and gearbox operation including slip and lock-up behaviour on a road test, then follow the model-specific procedure for pressure or flow tests.

How to fix

• Correct the fluid level and replace degraded fluid with the specified type, following the manufacturer's procedure.
• Clear or replace a restricted cooler, cooler lines, or repair any thermostat, bypass valve or cooling pump fault.
• Repair or replace damaged wiring and connectors, or replace the temperature sensor if it reads incorrectly.
• Repair or overhaul the gearbox where internal wear or torque converter clutch faults are generating excess heat.
• Rectify any engine cooling system fault affecting the gearbox cooler, then clear the code and road test to confirm it does not return.

Can I keep driving?

Nearby codes

• P0217GenericEngine Coolant Over Temperature Condition
• P0219GenericEngine Overspeed Condition