The primary source of heat in the transmission is the torque converter. Hot oil exits the torque converter through the torque converter clutch (TCC) control valve and flows to the transmission cooler supply line. The supply line connects to the cooler, which is in the radiator. From the cooler, the oil returns through the oil cooler return line and enters the lubrication circuits. After lubricating the internal components, the oil returns to the oil pan. The transmission fluid temperature (TFT) sensor is located in the control solenoid (w/body and TCM) valve assembly.

The TFT is -39 to +149°C (-38 to +300°F) for 5 seconds.

The TFT is greater than 140°C (284°F) for 1 minute.

DTC P0218 is a Type C DTC.

The Driver Information Center (DIC), if equipped, will display "TRANSMISSION HOT - Idle Engine" when the TFT reaches 132°C (270°F). The TFT on the scan tool should rise steadily to a normal operating temperature, and then stabilize. Ask about the customer's driving habits, trailer towing, etc. Trailer towing should occur in D4. Ensure the engine cooling system is functioning normally.

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

Component Connector End Views

DTC Type Reference

Electrical Information Reference

1. Review the Failure Records when the DTC set.

⇒	If the Engine Coolant Temperature (ECT) was above 125°C (257°F) when the DTC set, go to Engine Overheating and correct that concern first.

2. Perform the Transmission Fluid Check to verify correct fluid level and condition.

1. Inspect the transmission cooling system for restrictions or damage.
2. Perform the Transmission Fluid Cooler Flushing and Flow Test to verify proper transmission oil cooler flow.

⇒	If a concern is found, repair or replace the damaged components as necessary.

3. Perform the Line Pressure Check to verify proper transmission line pressure.

⇒	If a concern is found repair or replace the damaged components as necessary.

1. Repair or replace the automatic transmission cooler or lines as necessary.
2. Perform the Service Fast Learn Adapts.

1. With a scan tool, clear the DTCs.
2. Operate the vehicle long enough to ensure the engine has reached normal operating temperature and the TFT has stabilized between 80 and 98°C (176 and 208°F).
3. Observe the specific DTC, and ensure DTC P0218 has run and passed.
4. Check for any other DTCs that you have not diagnosed.