GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2009 🢒 Allure 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 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 provide an overview of each diagnostic category.

DTC Descriptors

DTC P0218 : Transmission Fluid Overtemperature

Diagnostic Fault Information

Component

Cause

DTC

DTC P0218 detects a very high transmission fluid temperature (TFT) without a TFT sensor malfunction.

Vehicle Overload or Beyond Towing Capacity
    • Vehicle is overloaded
    • Vehicle is towing beyond capacity
    • Towing in wrong gear
    • Vehicle modifications

P0218

Heat Transfer
    • Engine overheating
       - Engine coolant level low
       - Cooling system leak
       - Inspect the engine mechanical for worn, leaking, or cracked cylinder heads, or engine block
       - Old coolant
       - Incorrect coolant concentration level
       - Incorrect engine coolant
       - Radiator hose kinked or pinched
       - Radiator has restricted flow/blockage
    • Restricted air flow
       - Loose, missing or damaged radiator air seals or deflector - poor air flow
       - The radiator and air conditioning (A/C) condenser have air flow obstructions and may include a large number of bent fins
       - The cooling fans do not operate
       - Vehicle modifications
    • Restricted automatic transmission fluid flow
       - Aftermarket auxiliary cooler not installed correctly, incorrect flow direction - reversed flow
       - Restricted, blocked, or pinched transmission cooler lines
       - Cooler restrictions - restricted flow/blockage
       - Vehicle modifications

P0218

Transmission Abuse
    • Engine overheating
    • Excessive brake torque maneuvers
    •  Vehicle overloaded
    • Vehicle is towing beyond capacity
    • Vehicle modifications

P0218

Vehicle Damage
    • Damage to vehicle under carriage
    • Transmission bottom pan damage
    • Restricted air flow

P0218

Transmission Fluid
    • Fluid leaks
    • Low fluid level
    • Contaminated or poor fluid quality

P0218

Torque Converter
    • Inefficient pump
    • Torque converter failure - stator, pump, clutch, ballooning, or heat damaged
    •  Stuck on or locked up
    • Converter damage

P0218

Low Pump Output
    • Low fluid level
    • Blocked, damaged, or loose filter
    • Pinched or restricted cooler lines
    • Restricted cooler - damage or debris
    • Inefficient pump - worn

P0218

Clutch Slippage
    • Low fluid level
    • Low pump output

P0218

Circuit/System Description

Transmission fluid is drawn from the bottom pan through the filter, case assembly, channel plate assembly, control valve body assembly, and into the oil pump assembly. Fluid pressure leaving the pump is controlled by the pressure regulator valve and becomes the main supply of line pressure to the various components and hydraulic circuits. Hot fluid from the torque converter, the primary source of heat in the transmission, flows through the torque converter clutch (TCC) control valve into the oil cooler supply line. The oil cooler supply line connects to the oil cooler, which is located in the vehicle radiator and auxiliary oil cooler, if equipped. Cool fluid then returns by way of the oil cooler return line to lubricate the final drive assembly and other components along the output shaft. After lubricating the internal components, the oil returns to the oil pan. The TFT sensor, attached to the bottom of the valve body, is part of the internal transmission wire harness and not serviced separately. The normal TFT operating temperature is -40 to +151°C (-40 to +304°F).

Conditions for Running the DTC
    • No TFT DTC P0711, P0712, or P0713.
    • The ignition voltage is between 8.0 and 18.0 volts.
    • The TFT is -39 to +149°C (-38 to +300°F) for 5 seconds.

Conditions for Setting the DTC

The TFT is greater than 140°C (286°F) for 1 minute.

Action Taken When the DTC Sets
    • DTC P0218 is a type C DTC.
    • The transmission control module (TCM) freezes transmission adaptive functions.
    • If equipped, the driver information center (DIC) displays "TRANS HOT - IDLE ENGINE".

Conditions for Clearing the DTC

DTC P0218 is a type C DTC.

Diagnostic Aids
    • DTC P0218 detects a high transmission fluid temperature for a long period of time.
    • The DIC, if equipped, displays "TRANS 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 driving habits, trailer towing, etc. Trailer towing should occur in DRIVE D. Ensure the engine cooling system is functioning normally.

Reference Information

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

    •  Component Connector End Views
    •  Inline Harness Connector End Views

Description and Operation Reference

    •  Transmission General Description
    •  Transmission Component and System Description

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification
  1. Verify the transmission fluid is at the proper level by performing the Transmission Fluid Check.
  2. Ask about the customer driving habits, trailer towing, etc. Trailer towing should occur in D.
  3. Review the Failure Records when the DTC set. Verify the engine coolant temperature is less than 125°C (257°F).
    4. ⇒If greater than the specified value, refer to Engine Overheating.
  4. Ensure the engine cooling system is functioning normally/properly. The TFT on the scan tool should rise steadily to a normal operating temperature, and then stabilize.
  5. Inspect the transmission cooling system for restrictions or damage.
  6. 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 from the Freeze Frame/Failure Records data.
  7. Inspect for restricted air flow through the radiator and/or auxiliary cooler, if equipped, due to debris or damaged fins.
    8. ⇒If a concern is found, repair or replace the damaged components as necessary.
  8. Inspect the transmission cooling system and/or auxiliary cooler, if equipped, for kinked or damaged transmission cooler lines.
    9. ⇒If a concern is found, repair or replace the damaged components as necessary.
  9. Perform the Transmission Fluid Cooler Flushing and Flow Test to verify proper transmission oil cooler flow.
    10. ⇒ If a concern is found, repair or replace the damaged components as necessary.
  10. Perform the Line Pressure Check to verify proper transmission line pressure.
    11. ⇒ If the line pressure is low, refer to Incorrect Line Pressure.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.