Transmission

P0218 — Transmission Fluid Over Temperature

Severity: high Drive with care, to a shop

What P0218 means

The control unit reads the transmission fluid temperature sensor and sees that the fluid has climbed above its safe limit. Normally the fluid is cooled by a transmission cooler, often built into or paired with the radiator, and stays within its working range. Overheating wears clutches and seals quickly and breaks the fluid down.

Symptoms

  • Transmission over-temperature warning light on
  • Check engine light on
  • Slipping or harsh shifting
  • Limp mode with reduced performance
  • Burnt fluid smell or fluid leaks under the car

Possible causes

  1. Heavy load such as towing, mountain driving, or stop-and-go traffic
  2. Clogged or restricted transmission cooler or lines
  3. Low transmission fluid level
  4. Faulty fluid temperature sensor or damaged wiring
  5. Cooling fan or engine cooling system problem
  6. Corroded connector or damaged harness
  7. Rarely, a faulty control unit

How to diagnose

  1. Read all codes and freeze-frame data and note any other transmission or cooling codes
  2. Let the transmission cool, then check fluid level and condition (color, smell, debris) per your model's procedure
  3. Inspect the transmission and cooler lines for leaks or damage
  4. Compare the fluid temperature sensor reading on a cold start with the coolant temperature
  5. Check the sensor connector and wiring for corrosion, opens, or shorts to ground
  6. Test the cooling fan and the overall engine cooling system
  7. Check cooler and line flow for restrictions (flush or flow test)
  8. If internal wear is suspected, have the transmission professionally diagnosed

Common fixes

  • Correct the fluid level and replace burnt or contaminated fluid
  • Flush or replace the transmission cooler and lines
  • Replace the fluid temperature sensor or repair its wiring
  • Repair the cooling fan or engine cooling components
  • Have a specialist repair the transmission if internal parts are worn

Questions and answers

Can I drive with a P0218 code?

It's best not to. Heat quickly damages clutches and fluid. Stop, let the transmission cool, check the fluid level, and drive only short distances carefully until the cause is found.

What most often causes P0218?

Most often it's heavy load, low fluid, or a clogged transmission cooler. A bad temperature sensor or wiring is less common, so check the fluid and cooling first.

Will P0218 go away on its own?

The warning light may go out once things cool down, but the code stays stored. If the cause isn't fixed, overheating will return and shorten the transmission's life.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.