Circuit Description
The powertrain control module (PCM) energizes the torque converter clutch
pulse width modulated (TCC PWM) solenoid valve by grounding the control circuit.
This blocks the exhaust for TCC signal fluid and allows filtered
2-3 drive fluid to feed the TCC signal circuit. When the vehicle
operating conditions are appropriate for TCC application, the PCM
begins the TCC duty cycle to approximately 30 percent.
This allows TCC signal fluid pressure to move the converter
clutch shift valve into the apply position and direct regulated
apply fluid to the torque converter. The PCM then increases,
ramps, the duty cycle to approximately 60 percent, where
regulated apply fluid pressure, applies the converter clutch.
The vehicle application determines the TCC apply rate.
Once the TCC applies, the duty cycle immediately increases
to approximately 70 percent to achieve full apply pressure,
in the regulated apply fluid circuit.
The TCC PWM solenoid valve is de-energized by the PCM opening the control
circuit. This action allows the TCC signal fluid to exhaust through the solenoid
and blocks filtered 2-3 drive fluid from entering the TCC
signal circuit. The loss of fluid pressure in the TCC signal circuit
releases the TCC.
If the PCM detects low TCC slip when the TCC is commanded OFF, then
DTC P0742 sets. DTC P0742 is a type C DTC. For
California emissions vehicles DTC P0742 is a type B DTC.
Conditions for Running the DTC
| • | No MAP sensor DTCs P0106, P0107, or P0108. |
| • | No Transmission Component Slipping DTC P1870. |
| • | No TP sensor DTCs P0121, P0122 or P0123. |
| • | No VSS DTCs P0502 or P0503. |
| • | No ISS DTCs P0716 or P0717. |
| • | No TCC DTCs P0741 or P1860. |
| • | No TFP manual valve position switch DTC P1810. |
| • | The engine is running for greater than 7 seconds. |
| • | The system voltage is 8-18 volts. |
| • | The speed ratio is 0.95-2.18. |
| • | The engine torque must be between 169 N·m (125 lb ft)
and: |
| - | 6.0L: 542 N·m (400 lb ft) |
| - | 8.1L: 881 N·m (650 lb ft) |
| • | No TFP manual valve position switch change within 6 seconds. |
| • | The TFP manual valve position switch indicates D4. |
| • | The commanded gear is not 1st. |
| • | Engine speed is 800-4,400 RPM. |
| • | The throttle position (TP) is 12-100 percent. |
| • | The vehicle speed is 11-121 km/h (7-75 mph). |
| • | The engine vacuum is 0-105 kPa (0-15 psi). |
Conditions for Setting the DTC
| • | The TCC slip speed must be -15 to +15 RPM for at
least 3 seconds. |
| • | All conditions met for 4 occurrences. |
| • | The transmission fluid temperature (TFT) is 20-130°C
(68-266°F). |
Action Taken When the DTC Sets
| • | For California emission equipped vehicles, the PCM illuminates
the malfunction indicator lamp (MIL) during the second consecutive trip in
which the Conditions for Setting the DTC are met. For Federal
emission equipped vehicles, the MIL is not illuminated. |
| • | The PCM commands maximum line pressure. |
| • | 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,
California only, and Failure Records, California and Federal. |
| • | The PCM stores the DTC P0742 in PCM history during the
second consecutive trip, California, or the first trip, Federal, in which
the Conditions for Setting the DTC are met. |
Conditions for Clearing the MIL/DTC
| • | For California emissions, 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. |
| • | For California emissions, the PCM clears the DTC from PCM history
if the vehicle completes 40 warm-up cycles without an emission
related diagnostic fault occurring. |
| • | For Federal emissions, the PCM clears the DTC from PCM history
if the vehicle completes 40 warm-up cycles without a non-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
| • | If the TCC is mechanically stuck ON with the parking brake applied
and any gear range selected, the TCC fluid mechanically applies the TCC.
TCC fluid mechanically applying the TCC can cause an
engine stall. |
| • | DTC P0742 defaults to an elevated line pressure condition which
may result in partial TCC apply. This may produce an idle surge that could
stall the engine. |
| • | A stuck TP sensor may set a DTC P0742. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests the mechanical state of
the TCC. When the PCM commands the TCC solenoid OFF, the slip speed
should increase.
Step
| Action
| Value(s)
| Yes
| No
|
1
| Did you perform the Powertrain
Diagnostic System Check?
| --
| Go to
Step 2
| Go to
Diagnostic System Check - Engine Controls
in Engine Controls - 6.0L or
Diagnostic System Check - Engine Controls
in
Engine Controls - 8.1L
|
2
|
- Install a scan tool.
- 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. Using the Clear Info Function erases the Freeze
Frame and Failure Records from the PCM.
- Record the Freeze Frame and Failure Records.
- Clear the DTCs.
- Select scan tool TP angle and TP sensor.
- Apply the accelerator pedal.
Are the TP sensor values within the specified range?
| 0.2-0.9 V
at 0 percent to 4.5 V at 100 percent
| Go to
Step 3
| Go to Diagnostic
Aids
|
3
|
- Select scan tool TCC Slip Speed and TCC Duty Cycle.
- Drive the vehicle in the D4 to achieve FOURTH gear under steady
acceleration with a throttle angle greater than 12 percent.
Does the scan tool display a TCC slip speed of -10 to
+10 RPM while the displayed TCC duty cycle is 0 percent?
| --
| Go to
Step 4
| Go to Diagnostic Aids
|
4
| The TCC is mechanically stuck ON.
Perform the following inspections:
- Inspect the TCC PWM solenoid valve exhaust orifice for any restrictions.
- Inspect the converter clutch apply valve for the possibility of
being stuck in the apply position.
- Inspect the valve body gasket for misalignment or damage.
- Inspect for a restricted TCC release or apply passage.
- Inspect for restricted transmission cooler line.
Refer to
Torque Converter Clutch Stuck On
.
Did you find and correct the condition?
| --
| Go to
Step 5
| --
|
5
| Perform the following
procedure in order to verify the repair:
- Select DTC.
- Select Clear Info.
- Operate the vehicle under the following conditions:
| • | Operate the vehicle in D4 with the TCC duty cycle 0 percent
and throttle above 12 percent. |
| • | Ensure that the TCC slip speed is greater than 100 RPM
for 2 seconds. |
- Select Specific DTC.
- Enter DTC P0742.
Has the test run and passed?
| --
| System OK
| Go to
Step
1
|
