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 increases
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
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, 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 P0894. |
| • | No TP sensor DTCs P0121, P0122 or P0123. |
| • | No VSS DTCs P0502 or P0503. |
| • | No AT ISS DTCs P0716 or P0717. |
| • | No TCC DTCs P0741 or P1860. |
| • | No TFP manual valve position switch DTC P1810. |
| • | 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: |
| - | 4.8L: 542 N·m (400 lb ft) |
| - | 6.0L: 576 N·m (425 lb ft) |
| • | No TFP manual valve position switch change within 6 seconds. |
| • | The TFP manual valve position switch indicates D4. |
| • | The transmission fluid temperature (TFT) is 20-130°C
(68-266°F). |
| • | The commanded gear is not 1st. |
| • | Engine speed is 800-4,400 RPM. |
| • | The throttle position (TP) is 12-100 percent. |
| • | Vehicle speed is 11-121 km/h (7-75 mph). |
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. |
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, 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. |
| • | A stuck TP sensor may set a DTC P0742. |
| • | 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. |
Test Description
The number below refers to the step number 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 Diagnostic System Check - Engine Controls?
| --
| Go to
Step 2
| Go to
Diagnostic System Check - Engine Controls
in Engine Controls - 4.8L, 5.3L, and 6.0L
|
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% to 4.5 V at 100%
| Go to
Step
3
| Go to Diagnostic Aids
|
3
| Drive the vehicle in the D4 drive range in FOURTH gear under steady acceleration
with a TP sensor 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
|
- Inspect the transmission for the following conditions:
| • | Exhaust orifice in the TCC PWM solenoid valve clogged |
| • | Converter clutch apply valve stuck in the apply position |
| • | Restricted apply or release passage |
| • | Valve body gasket for misalignment or damage |
| • | Restricted transmission cooler line |
- Repair any of the above conditions as necessary.
Did you complete the repair?
| --
| 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?
| --
| Go to
Step 6
| Go to
Step 2
|
6
| With the 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 - 4.8L, 5.3L, and 6.0L
| System OK
|
