M99 - Automatic Transmission
DTC P0218
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptor
DTC P0218
- Transmission Fluid Overtemperature
Diagnostic Fault Information
Circuit/System Description
The primary source of heat in the transmission is the electric motors. The electric motors are cooled by the transmission fluid. Hot fluid exits the electric motors and flows to the transmission cooler supply line. The supply line connects to the cooler, which is in the radiator. From the cooler, the fluid returns through the oil cooler return line and enters the lubrication circuits. After lubricating the internal components, the fluid returns to the oil pan. The transmission fluid temperature (TFT) sensor is located in the control solenoid (w/body and TCM) valve assembly and is not serviced separately.
Conditions for Running the DTC
The TFT is -50 and +135°C (-58 and +275°F) for 5 seconds.
Conditions for Setting the DTC
The TFT is greater than 135°C (275°F) for 10 seconds.
Action Taken When the DTC Sets
* DTC P0218 is a Type C DTC.
* The TCM freezes transmission adaptive functions.
* The TCM shuts down and turns Off.
Conditions for Clearing the DTC
DTC P0218 is a Type C DTC.
Diagnostic Aids
The driver information center (DIC), if equipped, will display 'TRANSMISSION HOT- Idle Engine' when the TFT reaches 132°C (270°F). The TFT parameter 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 D or M range. Ensure the engine cooling system is functioning normally.
Reference Information
Schematic Reference
* Park - Engine Running (Park - Engine Running)
* EVT Mode Reverse - Engine Running (EVT Mode Reverse - Engine Running)
* Neutral - Engine Running (Neutral - Engine Running)
* EVT Mode Low - Engine Running (EVT Mode Low - Engine Running)
* EVT Mode Low - Engine Off (EVT Mode Low - Engine Off)
* Drive Range, First Gear (Drive Range, First Gear)
* Drive Range, Second Gear (Drive Range, Second Gear)
* Drive Range, Third Gear (Drive Range, Third Gear)
* Drive Range - Fourth Gear (Drive Range, Fourth Gear)
* EVT Mode High - From Drive Range 4th Gear (EVT Mode High - From Drive Range 4th Gear)
* Power Off Low Default (Power Off Low Default)
* Power Off High Default (Power Off High Default)
* Fluid Passages (Fluid Passages)
Connector End View Reference
Component Connector End Views
Electrical Information Reference
* Circuit Testing
* Connector Repairs
* Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs
* High Voltage Disabling
* High Voltage Enabling
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Circuit/System Verification
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, refer to Engine Overheating and correct that concern first.
2. Perform the transmission fluid checking procedure. Refer to Transmission Fluid Check (Transmission Fluid Check) .
Circuit/System Testing
1. Inspect the transmission cooling system for restrictions or damage.
• If a concern is found, repair or replace the restricted or damaged components as necessary.
2. Perform the Transmission Fluid Cooler Flushing and Flow Test (J 45096) (Automatic Transmission Oil Cooler Flushing and Flow Test (J 45096)) .
• If a concern is found, repair or replace the damaged components as necessary.
3. Perform the automatic transmission Line Pressure Check (Line Pressure Check) procedure.
• If a concern is found repair or replace the damaged components as necessary.
4. Perform the automatic transmission Electric Motor Test Procedure.
• If a concern is found repair or replace the damaged components as necessary.
Component Testing
* Perform the Fluid Leak Diagnosis (Fluid Leak Diagnosis) .
* Perform the Transmission Fluid Check (Transmission Fluid Check) procedure.
* Perform the Line Pressure Check (Line Pressure Check) procedure.
* Perform the High or Low Line Pressure check.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
1. Repair or replace the automatic transmission cooler or lines as necessary. Refer to Transmission Fluid Cooler Pipe Replacement (Service and Repair) .
2. Repair or replace the automatic transmission electric motors as necessary. Refer to Transmission Electric Motor 1 Replacement or Transmission Electric Motor 2 Replacement.
Repair Verification
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 80-98°C (176-208°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.