GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 1999 🢒 Century 🢒 DTC 🢒 DTC P0218 Transmission Fluid Overtemperature

Object Number: 360646 Size: LF
Automatic Transmission Components
Automatic Transmission Controls Schematics
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The transmission fluid temperature (TFT) sensor is a negative coefficient thermistor. When the transmission fluid is cold, the sensor resistance is high. As the transmission fluid warms, the sensor resistance decreases. The TFT range is -40 to +150°C (-40 to +302°F).

When the PCM detects a low TFT sensor resistance (high transmission temperature) for an extended period of time, then DTC P0218 sets. DTC P0218 is a type D DTC.

Conditions for Running the DTC

No TFT DTCs P0711, P0712 or P0713.

Conditions for Setting the DTC

DTC P0218 sets when the transmission fluid temperature is greater than 130°C (266°F) for more than 10 minutes.

Action Taken When the DTC Sets

The PCM does not illuminate the malfunction indicator lamp (MIL).

Conditions for Clearing the DTC
    • A scan tool clears the DTC from PCM history.
    • The PCM clears the DTC from PCM history if the vehicle completes 40 consecutive warm-up cycles without a non-emission related diagnostic fault occurring.

Diagnostic Aids
    • Inspect the wiring at the PCM, the transmission connector and all other circuit connecting points for the following conditions:
       - A backed out terminal
       - A damaged terminal
       - Reduced terminal tension
       - A chafed wire
       - A broken wire inside the insulation
       - Moisture intrusion
       - Corrosion
    • Check for a faulty TFT sensor by reading resistance at various temperature levels, and comparing to the Temperature vs Resistance table.
    • When diagnosing for an intermittent short or open condition, massage the wiring harness while watching the test equipment for a change.
    • Inspect the transmission cooling system for blockage and restrictions.

Test Description

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

  1. This step determines if an electrical condition exists.

  2. This step checks the TFT sensor against the Temperature vs Resistance table.

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

2

Perform the Transmission Fluid Checking Procedure.

Have you performed the Transmission Fluid Checking Procedure?

--

Go to Step 3

Go to Transmission Fluid Check

3

Allow the transmission to cool for at least 45 minutes.

  1. Install the Scan Tool .
  2. With the engine OFF, turn the ignition switch to the RUN position.

    3. Important: Before clearing the DTCs, use the scan tool in order to record the Failure Records. Using the Clear Info function erases the Failure Records from the PCM.

  3. Record the Failure Records.
  4. Clear the DTC.
  5. Select Transmission Fluid Temperature on the scan tool.

Is the Transmission Fluid Temperature (TFT) equal to or greater than the specified value?

130°C (266°F)

Go to Step 5

Go to Step 4

4

Inspect for the following conditions:

    • The engine is overheating. Check engine coolant temperature, coolant level, hoses.
    • The vehicle is overloaded.
    • The fluid is contaminated with antifreeze.
    • The filter is clogged.
    • The filter is not properly seated.
    • Clogged or restricted cooler lines. Refer to Automatic Transmission Oil Cooler Flow Test .
    • The radiator is restricted.
    • The vacuum line to the vacuum modulator is restricted or leaking.

Was a condition found and corrected?

--

Go to Step 10

Go to Diagnostic Aids

5

Let the transmission cool to ambient temperature.

  1. Disconnect the Automatic Transmission 7-way connector (additional DTCs will set).
  2. Install jumper harness J 38835 to the 7-way connector on the transmission.
  3. Connect a J 39200 digital multimeter (DMM) from terminal F to terminal G using a J 35616-A connector test adapter kit.

    4. Refer to Automatic Transmission Inline Harness Connector End View .

Is the measured resistance within the specified range?

3164-3867 ohms @ 20°C (68°F) (If temperature and resistance are different, refer to Temperature vs Resistance Table)

Go to Step 6

Go to Step 8

6

Check circuit 1227 for a possible short to ground.

Was a condition found?

--

Go to Step 9

Go to Step 7

7

Replace the PCM.

Refer to Powertrain Control Module Replacement/Programming in Engine Controls.

Is the replacement complete?

--

Go to Step 10

--

8

Replace the TFT sensor.

Refer to Fluid Temperature Sensor Replacement .

Is the replacement complete?

--

Go to Step 10

--

9

Repair the wiring as needed.

Refer to General Electrical Diagnosis in Wiring Systems.

Is the repair complete?

--

Go to Step 10

--

10

Perform the following in order to verify the repair:

  1. Select DTC.
  2. Select Clear Info.
  3. Operate the vehicle under the following conditions:
    4. • Turn the ignition switch to the RUN position for at least 5 seconds.
    • The TFT must be less than 129°C (264°F).
  4. Select Specific DTC.
  5. Enter DTC P0218.

Has the test run and passed?

--

System OK

Go to Step 1