GM Service Manual Online
For 1990-2009 cars only

Object Number: 154212  Size: LF
Automatic Transmission Controls Schematics
OBD II Symbol Description Notice

Circuit Description

The flow of transmission fluid starts in the bottom pan and is drawn through the filter, control valve body assembly, transmission case and into the oil pump assembly. The oil pump assembly pressurizes the fluid and directs it to the pressure regulator valve where it becomes the main supply of fluid to the various components and hydraulic circuits in the transmission. Hot fluid exiting the torque converter flows through the converter clutch apply valve and into the transmission cooler lines to the oil cooler located in the vehicle radiator (and auxiliary cooler if equipped). From the cooler, fluid returns to cool and lubricate the front of the transmission. In forward drive ranges, D4 fluid from the manual valve is routed through an orificed cup plug in the rear of the transmission case to feed the rear lube fluid circuit.

When the vehicle control module (VCM) detects a high transmission fluid temperature (TFT) for a long period of time, then DTC P0218 sets. DTC P0218 is a type C DTC.

Conditions for Running the DTC

    • No TFT sensor DTCs P0711, P0712 or P0713.
    • The ignition switch is in the RUN position for 5 seconds.

Conditions for Setting the DTC

The TFT is greater than 130°C (266°F) for 600 seconds (10 minutes).

Action Taken When the DTC Sets

    • The VCM does not illuminate the malfunction indicator lamp (MIL).
    • The VCM freezes shift adapts from being updated.
    • The VCM records the operating conditions when the Conditions for Setting the DTC are met. The VCM stores this information as Failure Records.
    • The VCM stores DTC P0218 in VCM history.

Conditions for Clearing the DTC

    • A scan tool can clear the DTC.
    •  The VCM clears the DTC from VCM history if the vehicle completes 40 warm-up cycles without a non-emission-related diagnostic fault occurring.
    • The VCM cancels the DTC default actions when the fault no longer exists and/or the ignition switch is OFF long enough in order to power down the VCM.

Diagnostic Aids

    • The scan tool Trans. Fluid Temp. should rise steadily to a normal operating temperature, then stabilize.
    • Ask about the customer's driving habits, trailer towing, etc. Trailer towing should occur in D3.
    • Refer to Symptom Diagnosis .

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step checks for air flow restrictions or damage which may result in the transmission overheating.

DTC P0218 Transmission Fluid Overtemperature

Step

Action

Value(s)

Yes

No

1

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check in Engine Controls

2

  1. Install a Scan Tool .
  2. With the engine OFF, turn the ignition switch to the RUN position.
  3. Important: Before clearing the DTC, use the Scan Tool in order to record the Failure Records. Using the Clear Info function erases the Failure Records from the VCM.

  4. Record the DTC Failure Records.
  5. Clear the DTC.
  6. Perform the transmission fluid checking procedure. Refer to Transmission Fluid Check .

Was the fluid checking procedure performed?

--

Go to Step 3

Go to Transmission Fluid Check

3

  1. Inspect the engine cooling system and transmission cooling system for the following conditions:
  2. • Air flow restrictions
    • Air flow blockage
    • Debris
  3. Inspect the transmission cooling system for damaged cooler lines.
  4. Test the oil cooler flow.
  5. Refer to Transmission Fluid Cooler Flushing and Flow Test .

Was a condition found?

--

Go to Step 6

Go to Step 4

4

Perform the line pressure check procedure.

Refer to Line Pressure Check .

Was a condition found?

--

Go to Step 6

Go to Step 5

5

Inspect the torque converter stator for damage.

Refer to Torque Converter Diagnosis .

Was a condition found?

--

Go to Step 6

Go to Diagnostic Aids

6

Perform the following procedure in order to verify the repair:

  1. Install a Scan Tool .
  2. Select DTC.
  3. Select Clear Info.
  4. Start and idle the engine until it reaches normal operating temperature.
  5. Monitor Engine Run Time and Trans. Fluid Temp. on the Scan Tool .
  6. Drive the vehicle for 10 minutes.
  7. Ensure that the transmission fluid temperature has stabilized and is less than 125°C (257°F).
  8. Select Specific DTC.
  9. Enter DTC P0218.

Has the test run and passed?

--

System OK

Go to Step 1