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

### Circuit Description

The TCC release switch is part of the automatic transmission fluid pressure (TFP) manual valve position switch. The TFP manual valve position switch is mounted to the transmission valve body.

The TCC release switch is a normally-closed switch. When the TCC is released, TCC release fluid pressure opens the TCC release switch which opens the TCC release pressure circuit. When the voltage on the circuit is high (switch open), the PCM recognizes that the TCC is no longer engaged.

If the PCM detects that the TCC release switch is closed when the TCC is commanded OFF, then DTC P0742 sets. DTC P0742 is a type A DTC.

### Conditions for Running the DTC

• | No TP sensor DTC P0121, P0122 or P0123.

• | No TCC PWM solenoid valve DTC P1860.

• | No TCC release switch DTC P1887.

• | The engine speed is greater than 500 RPM and not in fuel shut off.

• | Engine torque is 95-270 N·m (70-200 lb ft).

• | The TP angle is 5-45%.

• | The transmission fluid temperature is 20-130°C (68-266°F).

• | The time since the last gear range change is greater than 6 seconds.

• | The speed ratio is less than 7.0.

• | The TCC is commanded OFF.

• | Slip speed is -20 to +25 for 8 seconds.

### Conditions for Setting the DTC

The TCC release switch is closed 6 times for 4 seconds each, during one trip.

### Action Taken When the DTC Sets

• | The PCM illuminates the malfunction indicator lamp (MIL).

• | The PCM commands the TCC ON at maximum capacity.

• | The PCM freezes shift adapts.

• | The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Freeze Frame and Failure Records.

• | The PCM stores DTC P0742 in PCM history.

### Conditions for Clearing the MIL/DTC

• | The PCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.

• | A scan tool can clear the MIL/DTC.

• | The PCM clears the DTC from the PCM history if the vehicle completes 40 consecutive warm-up cycles without an emission-related diagnostic fault occurring.

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

### Diagnostic Aids

• | Inspect the connectors at the controller, the component and all other circuit connecting points for an intermittent condition. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

• | Inspect the circuit wiring for an intermittent condition. Refer to Testing for Electrical Intermittents in Wiring Systems.

• | Rapid fluctuation in line pressure could set DTC P0742.

• | An open condition in the TCC release circuit or switch would set DTC P1887. Open circuits are not diagnosed in DTC P0742.

• | Inspect for a pressure regulator condition.

• | Inspect for abnormal line pressure.

• | The customer may notice an engine stalling condition.

### Test Description

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

1. A Yes answer indicates that the TCC is functioning properly.

2. By disconnecting the transmission connector, the PCM should interpret the open circuit as TCC release pressure present. A Yes answer indicates that the engine side of the circuit is functioning properly.

3. This step tests for a mechanical or hydraulic condition.

#### DTC P0742 TCC System -- Stuck On

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain Diagnostic System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check in Engine Controls
2 | Did you perform the transmission fluid checking procedure? | -- | Go to Step 3 | Go to Transmission Fluid Check
3 |

1. Install a Scan Tool .
2. Turn ON the ignition with the engine OFF.

Important: Before clearing the DTCs, use the Scan Tool in order to record the Freeze Frame and Failure Records for reference. The Clear Info function will erase the data.

3. Record the DTC Freeze Frame and Failure Records, then clear the DTCs.
4. With a Scan Tool , observe the TCC release pressure status.
5. Start the engine.

Does the Scan Tool indicate Yes for TCC release pressure?

--

Go to Diagnostic Aids

Go to Step 4

4 |

1. Turn OFF the ignition.
2. Disconnect the transmission 20-way connector.
3. Turn ON the ignition with the engine OFF (additional DTCs may set).

Does the Scan Tool indicate Yes for TCC release pressure?

--

Go to Step 5

Go to Step 6

5 | Test the signal circuit (CKT 1804) of the TCC release switch for a short to ground between the AT inline 20-way connector and the TFP manual valve position switch. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find the condition? | -- | Go to Step 10 | Go to Step 7
6 | Test the signal circuit (CKT 657) of the TCC release switch for a short to ground between the PCM connector C2 and the AT inline 20-way connector. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 11
7 |

1. Remove the TFP manual valve position switch.
2. Inspect the TCC release switch for the following conditions:

• | A damaged or leaking seal

• | Sediment or debris

• | Damaged switch contacts

• | Stuck switch contacts

Did you find a condition?

--

Go to Step 8

Go to Step 9

8 | Replace the TFP manual valve position switch. Refer to Transmission Fluid Pressure Manual Valve Position Switch Replacement . Did you complete the replacement? | -- | Go to Step 12 | --
9 |

1. Inspect for the following conditions:

Refer to Transmission Overhaul in the 4T65-E Section of the Transmission Unit Repair Manual.

• | TCC control valve stuck

• | TCC feed limit valve stuck

• | TCC regulator apply valve stuck

• | TCC PWM solenoid valve stuck

• | Pressure regulator valve stuck

2. Repair or replace any malfunctioning components.

Did you find and correct a condition?

--

Go to Step 12

--

10 | Replace the transmission wiring harness assembly. Refer to Wiring Harness Replacement . Did you complete the replacement? | -- | Go to Step 12 | --
11 | Replace the PCM. Refer to Powertrain Control Module Replacement/Programming in Engine Controls. Did you complete the replacement? | -- | Go to Step 12 | --
12 | In order to verify your repair, perform the following procedure:

1. Select DTC.
2. Select Clear Info, then clear the DTCs.
3. Drive the vehicle in D4.

• | The throttle position must be 35-45%

• | The time since the last gear range change must be greater than 6 seconds

• | The TCC must be commanded OFF

• | Slip speed must be 150-200 RPM

• | The TCC release switch must be open, indicating TCC release pressure is present, for 5 seconds.

4. Select specific DTC.
5. Enter DTC P0742.

Has the test run and passed?

--

System OK

Go to Step 1