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For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 1999 🢒 Eldorado 🢒 Transmission/Transaxle 🢒 Automatic Transaxle - 4T80-E 🢒 DTC P0742 TCC System Stuck On

Object Number: 25442 Size: SF
Automatic Transmission Components
Automatic Transmission Controls Schematics
OBD II Symbol Description Notice

Circuit Description

The PCM controls the torque converter clutch (TCC) solenoid valve pulse width modulation (PWM). The solenoid controls the hydraulic fluid for TCC apply and release. When the vehicle is accelerating, the PCM commands the TCC to be disengaged.

If the PCM detects a TCC slip from +50 to +135 RPM, when the TCC is commanded OFF, then DTC P0742 sets. DTC P0742 is a Type B DTC.

Conditions for Running the DTC
    • No MAF DTCs P0101, P0102, or P0103.
    • No TP DTCs P0121, P0122, or P0123.
    • No VSS DTCs P0502 or P0503.
    • No A/T ISS DTCs P0716 or P0717.
    • No TCC Stuck OFF DTC P0741.
    • No TFP manual valve position switch DTC P1810.
    • No TCC PWM solenoid valve DTC P1860.
    • The engine run time is greater than 5 seconds.
    • The engine is not in fuel cut off.
    • The TFP manual valve position switch indicates D4.
    • The transmission gear ratio indicates 2nd, 3rd or 4th gear.
    • The throttle angle is greater than 15.3 degrees.
    • The delivered torque is 160-220 N·m (118-162 lb ft).
    • The TCC is commanded OFF.

Conditions for Setting the DTC

The slip speed is +50 to +135 RPM for 5 seconds (slip speed equals engine speed minus transmission input shaft speed).

Action Taken When the DTC Sets
    • The PCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met.
    • SERVICE ENGINE SOON, SERVICE TRANSMISSION displays on the driver information center (DIC).
    • The PCM inhibits TCC engagement.
    • The PCM inhibits 4th gear if the transmission is in hot mode.
    • The PCM stores DTC P0742 in PCM history during the second consecutive trip in which the Conditions for Setting the DTC are met.

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 clears the DTC from PCM history.
    • The PCM clears the DTC from PCM history if the vehicle completes 40 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 transmission fluid for sediment or debris.

Test Description

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

  1. This step verified that the PCM commanded the TCC PWM solenoid valve OFF and the slip speed is +50 to +135 RPM for more than 5 seconds.

    2.

  2. This step inspects and repairs the components that caused the DTC to set.

DTC P0742 TCC System Stuck On

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

  1. Install the Scan Tool .
  2. Turn the ignition switch to the RUN position.

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

  3. Record the Freeze Frame and Failure Records.
  4. Clear the DTCs.
  5. Drive the vehicle in the D4 drive range, in FOURTH gear under steady acceleration, with a throttle angle greater than 25%.

While the TCC Duty Cycle is 0%, does the scan tool display a TCC slip speed less than the specified value?

135 RPM

Go to Step 3

Go to Diagnostic Aids

3

  1. Inspect for the following conditions:
    2. • The TCC PWM solenoid valve is stuck ON due to sediment.
    • The TCC converter feed limit valve is stuck ON due to sediment.
  2. Repair or replace any malfunctioning component.

Refer to Unit Repair.

Is the repair complete?

--

Go to Step 4

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4

Perform the following procedure in order to verify the repair:

  1. Select DTC.
  2. Select Clear Info.
  3. Operate the vehicle under the following conditions:
    4. 3.1. Road test the vehicle.
    3.2. The slip speed must be greater than +80 RPM, or less than -5 RPM, for 4 seconds.
  4. Select Specific DTC. Enter DTC P0742.

Has the test run and passed?

--

System OK

Go to Step 1