GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2008 🢒 XLR 🢒 Transmission/Transaxle 🢒 Automatic Transmission - 6L50/6L80/6L90 🢒 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

Component

Cause

DTCs

Engine
    • Engine coolant level low
    • Incorrect engine coolant
    • Old coolant or incorrect concentration level
    • Cooling system leak
    • Radiator hose kinked or pinched
    • Loose, missing, or damaged radiator air seals or deflector - poor air flow
    •  The radiator and A/C condenser has air flow obstructions to include large amount of bent fins
    • The cooling fans do not operate
    • Inspect the engine mechanical for worn, leaking, cracked cylinder heads, or engine block.

P1258

Transmission

Vehicle Overload or Beyond Capacity Towing:

    • Vehicle is overloaded.
    • Vehicle is towing beyond capacity.
    • Towing in wrong gear.
    • Vehicle modifications

P0218

Heat transfer:

    • Engine overheating
    • Cooler restrictions - radiator has restricted flow/blockage
    • Restricted air flow
    • Vehicle modifications
    • Aftermarket auxiliary cooler installed incorrectly, incorrect flow direction - reversed flow
    • Restricted, blocked, or pinched transmission cooler lines

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

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.

Conditions for Running the DTC
    • Ignition voltage is at lease 8.6 volts, but no more than 19.0 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 (284°F) for 1 minute.

Action Taken When the DTC Sets
    • DTC P0218 is a Type C DTC.
    • The TCM freezes the transmission adaptive function.

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 on the scan tool should rise steadily to a normal operating temperature, and then stabilize.

Ask the customer whether their typical day-to-day driving include:

    • Trailer towing
    • Hauling or vehicle over-loading
    • Hot climate driving
    • Extended idling
    • Extreme off-road conditions

Trailer towing should occur in D4. Ensure the engine cooling system is functioning normally.

Reference Information

Schematic Reference

    •  Park - Engine Running
    •  Reverse
    •  Neutral - Engine Running
    •  Drive Range, First Gear Engine Braking
    •  Drive Range, First Gear
    •  Drive Range, Second Gear
    •  Drive Range, Third Gear
    •  Drive Range, Third Gear Default
    •  Drive Range - Fourth Gear
    •  Drive Range, Fifth Gear
    •  Drive Range, Fifth Gear Default
    •  Drive Range, Sixth Gear
    •  Fluid Passages
    •  Engine Cooling Schematics

Description and Operation

    •  Transmission General Description
    •  Transmission Indicators and Messages

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Circuit/System Verification
  1. Review the Failure Records when the DTC set.
    2. ⇒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.

Circuit/System Testing
  1. Inspect the transmission cooling system for restrictions or damage, inducing any auxiliary cooler if equipped.
  2. Perform the Transmission Fluid Cooler Flushing and Flow Test to verify proper transmission oil cooler flow.
    3. ⇒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.
    4. ⇒If a concern is found repair or replace the damaged components as necessary.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Repair or replace the automatic transmission cooler or lines as necessary. Refer to Transmission Fluid Cooler Pipe Replacement - Rear and Transmission Fluid Cooler Upper Pipe Assembly Replacement .