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Test Description

WARNING: This page is about a different car, the 2004 Pontiac Aztek and 2004 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.

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

  1. 2:  A Yes answer indicates that the TCC release switch is functioning properly.
  2. 4:  With the 20-way connector disconnected, the TCM should interpret the open circuit as TCC release pressure present.
  3. 5:  The TCC release switch is a normally closed switch and must be disconnected to properly test for a short to ground condition. An open condition in the TCC release circuit or switch would set DTC P1887. Open circuits are not diagnosed in DTC P0742.
  4. 8:  This step tests for a mechanical or hydraulic condition that would cause the TCC to be stuck ON.
DTC P0742 (3.6L)

Step Action Value(s) Yes No
1 Did you perform the Diagnostic System Check - Engine Controls? - Go to Step 2  Go to Diagnostic System Check - Engine Controls in Engine Controls - 3.6L
2 
  1. Install a scan tool.
  2. Turn ON the ignition with the engine OFF.
    3. 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.
  4. Clear the DTCs.
  5. Start the engine.
  6. With a scan tool, observe the TCC Release Pressure status.
Does the scan tool indicate Yes for TCC Release Pressure?		 - Go to Step 3  Go to Step 4 
3
  1. Drive the vehicle above 72 km/h (45 mph) in D3 or D4, with a TP angle of 5-90%.
  2. With the scan tool, command the TCC PWM solenoid valve ON and observe TCC Release Pressure.
  3. With the scan tool, command the TCC PWM solenoid valve OFF and observe TCC Release Pressure.
While the TCC was commanded OFF did the TCC release pressure indicate NO at any time?		 - Go to Step 8  Go to Diagnostic Aids
4 
  1. Turn OFF the ignition.
  2. Disconnect the AT inline 20-way connector. Additional DTCs may set.
  3. Turn ON the ignition with the engine OFF.
  4. Observe the TCC Release Pressure status.
Does the scan tool indicate Yes for TCC release pressure?		 - Go to Step 5  Go to Step 6 
5  Disconnect the transmission internal wiring harness from the TFP manual valve position switch.
Test the signal circuit 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 Testing for Short to Ground and Wiring Repairs in Wiring Systems.
Did you find the condition?		 - Go to Step 10  Go to Step 7 
6 Test the signal circuit of the TCC release switch for a short to ground between the TCM connector and the AT inline 20-way connector.
Refer to Testing for Short to Ground 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 9  Go to Step 8 
8 
  1. Inspect for the following conditions:
    • TCC control valve stuck in the apply position
    • TCC PWM solenoid valve stuck, exhaust restricted or faulty internal O-ring
    • TCC fluid circuits leaking

      Refer to Control Valve Body Disassemble (Without Touch Activated Power) Control Valve Body Disassemble (With Touch Activated Power) in Transmission Unit Repair article.

    • The TCC blowoff valve or spring for damage or not seating

      Refer to Case Cover Components Inspection in Transmission Unit Repair article.

    • Turbine shaft seals for leaks

      Refer to Torque Converter Assembly Removal in Transmission Unit Repair article.

    • Pump shaft seal for leaks

      Refer to Oil Pump Drive Shaft Assemble in Transmission Unit Repair article.

    • Spacer plate gaskets torn/leaking

      Refer to Control Valve Body and Spacer Plate Assemble in Transmission Unit Repair article.

    • Pressure regulator valve stuck

      Refer to Control Valve Body Disassemble (Without Touch Activated Power) Control Valve Body Disassemble (With Touch Activated Power) in Transmission Unit Repair article.

    • Abnormally high or low line pressure. Refer to Line Pressure Check Procedure .
  2. Repair or replace any malfunctioning components.
Did you find and correct a condition?		 - Go to Step 12  Go to Diagnostic Aids
9 Replace the TFP manual valve position switch.
Refer to Transmission Fluid Pressure (TFP) Manual Valve Position Switch Replacement .
Did you complete the replacement?		 - 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 TCM.
Refer to Module, Transmission Control - Replace .
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.
  3. Operate the vehicle under the following conditions:
    • Drive the vehicle in a DRIVE range.
    • TP angle must be 5-90 percent.
    • The TCC must be commanded OFF.
    • The TCC release switch must be open, indicating TCC release pressure is not applied, for 2 seconds.
  4. Select specific DTC.
  5. Enter DTC P0742.

Has the test run and passed?		 - Go to Step 13  Go to Step 2 
13 With a scan tool, observe the stored information, capture info and DTC info.
Does the scan tool display any DTCs that you have not diagnosed?		 - Go to Diagnostic Trouble Code (DTC) List in Engine Controls - 3.6L System OK
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