DTC P1874 Torque Conv Stator Temp Switch CKT High. Buick Roadmaster 1996

For 1990-2009 cars
Automatic Transmission Components
Automatic Transmission Controls Schematics
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The torque converter stator temperature switch is a normally-open, temperature-sensitive switch which sends a signal to the PCM to begin action in order to cool the torque converter. At transmission fluid temperatures of 164°C (327°F) or higher, the switch closes and the signal to the PCM changes to 0 volts. The torque converter stator temperature switch is a single lead switch that grounds through the transmission fluid cooler pipes.

When the PCM detects that the torque converter stator switch does not indicate a hot mode at a high transmission temperature, then DTC P1873 sets. DTC P1873 is a type D DTC.

### Conditions for Setting the DTC

• | No TFT DTCs P0712 or P0713.

• | The TFT is less than 140°C (284°F).

• | The torque converter stator temperature switch circuit does not indicate hot mode.

• | All conditions are met for 15 seconds.

### Action Taken When the DTC Sets

• | The torque converter stator temperature switch indicates a hot mode.

• | The PCM freezes shift adapts from being updated.

• | The PCM does not illuminate the Malfunction Indicator Lamp (MIL).

### Conditions for Clearing the DTC

• | A scan tool can clear the DTC from the PCM history. The PCM clears the DTC from the PCM history if the vehicle completes 40 warm-up cycles without a failure reported.

• | The PCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the PCM.

### Diagnostic Aids

• | If the switch and the external wiring are OK, verify the circuit ground integrity through the transmission fluid cooler pipes.

• | Inspect the wiring for poor electrical connections at the PCM. Inspect the wiring for poor electrical connections at the transmission 20-way connector. Look for the following conditions:

- | A bent terminal

- | A backed out terminal

- | A damaged terminal

- | Poor terminal tension

- | A chafed wire

- | A broken wire inside the insulation

• | When diagnosing for an intermittent short or open condition, massage the wiring harness while watching the test equipment for a change.

### Test Description

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

1. This step verifies the electrical integrity of the wiring and the PCM.

#### 1874 Torque Converter Stator Temperature Switch Circuit-High Input

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 automatic transmission fluid checking procedure. Refer to Transmission Fluid Check . Did you perform the transmission fluid checking procedure? | -- | Go to Step 3 | Go to the Transmission Fluid Check

3

1. Install the scan tool.
2. With the engine OFF, turn the ignition switch to the RUN position.

Important: Before clearing the DTCs, use the scan tool in order to record Failure Records for reference. The Clear Info function will erase the data.

3. Record the DTC Failure Records.
4. Disconnect the torque converter stator temperature switch.
5. Using a grounded test lamp, probe the torque converter stator temperature switch connector.

Does the scan tool display "TCC Stator Temp. as High (closed switch) with the test lamp connected, and Normal (open switch) with the test lamp disconnected?

--

Go to Step 6

Go to Step 4

4 | Is Normal (open switch) displayed at all times? | -- | Go to Step 5 | Go to Diagnostic Aids

5

1. Inspect circuit 585 for an open or short to battery voltage.
2. Repair circuit 585 if necessary. Refer to Electrical Diagnosis, Section 8.

Is the repair complete?

--

Go to Step 7

--

6 | Replace the torque converter stator temperature switch. Is the replacement complete? | -- | Go to Step 7 | --

7

In order to verify your repair, perform the following procedure:

1. Select DTC.
2. Select Clear Info.
3. Ensure that the torque converter stator temperature switch circuit indicates a hot mode when the transmission fluid temperature is greater than 140°C (284°F) for at least 15 seconds.
4. Select Specific DTC.
5. Enter DTC P1874.

Has the test run and passed?

--

System OK

Begin diagnostic again. Go to Step 1