Allison - Automatic Transmission

DTC P0218

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.

DTC Descriptor
DTC P0218
- Transmission Fluid Overtemperature

Circuit/System Description

The transmission fluid temperature (TFT) sensor is a 2 wire sensor located in the pressure switch manifold (PSM). The transmission control module (TCM) supplies the TFT signal circuit and a low reference circuit. The resistance of the TFT sensor decreases as the oil temperature increases. The TCM monitors the voltage drop across the TFT sensor and calculates the temperature of the transmission fluid in the sump.

Conditions for Running the DTC

* DTC P0711, P0712, or P0713 is not set.
* Engine speed is greater than 200 RPM for 5 seconds.
* Ignition and battery voltage is between 9 and 18 V.
* TFT is less than 150° C (302° F).

Conditions for Setting the DTC

This DTC sets when the transmission sump temperature is 122°C (251°F) or greater for 10 seconds.

Action Taken When the DTC Sets

* DTC P0218 is a Type C DTC.
* The TCM changes to the Hot Mode shift schedule to increase engine speed and improve cooler flow.

Conditions for Clearing the DTC

DTC P0218 is a Type C DTC.

Diagnostic Aids

* Ask about the customer's driving habits, trailer towing, etc. Trailer towing should occur in tow haul mode.
* Ensure the engine cooling system is functioning normally.

Reference Information
Schematic Reference

Automatic Transmission Controls Schematics (Allison - Automatic Transmission)
Connector End View Reference

* Component Connector End Views (Connector End Views By Name)
* Inline Harness Connector End Views (Connector End Views By Number)

Description and Operation

* Transmission General Description (Transmission General Description)
* Transmission Component and System Description (Transmission Component and System Description)
* Electronic Component Description (Electronic Component Description)

Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference

Control Module References (Control Module References) for scan tool information

Circuit/System Verification

1. Review the Freeze Frame/Failure Records when the DTC set. Verify the engine coolant temperature was less than 125°C (257°F).

• If greater than the specified range, refer to Engine Overheating (Engine Overheating).

2. Inspect the transmission cooling system for restrictions or damage.
3. Prior to cold start, ignition ON, observe the Trans. Fluid Temp. parameter with a scan tool. The Trans. Fluid Temp. parameter should be approximately the same as ambient temperature.
4. Perform the Transmission Fluid Level and Condition Check (Transmission Fluid Level and Condition Check) to verify correct fluid level and condition.
5. Perform the Transmission Fluid Cooler Flushing and Flow Test (Transmission Fluid Cooler Flushing and Flow Test) to verify proper transmission oil cooler flow.
6. Perform the Line Pressure Check (Line Pressure Check) to verify proper transmission line pressure.
7. Perform the Road Test (Allison - Automatic Transmission) while observing the Trans. Fluid Temp. parameter with a scan tool. The Trans. Fluid Temp. parameter should rise steadily to a normal operating temperature, and then stabilize.
8. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed on the Freeze Frame/Failure Records data.

Circuit/System Testing

Note: You must perform the Circuit/System Verification first.

Refer to Transmission Overheats (Transmission Overheats).

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

Transmission Overheats (Transmission Overheats)

Repair Verification

If another DTC is present, refer to Diagnostic Trouble Code (DTC) List - Vehicle (Diagnostic Trouble Code (DTC) List - Vehicle) and perform the appropriate diagnostic procedure.