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 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 P0894. |
| • | 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 P2761. |
| • | 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 169-576 N·m (125-425 lb ft). |
| • | The transmission fluid temperature (TFT) is 20-130°C (68-266°F). |
| • | 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). |
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, 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 which may result in partial
TCC apply. This may produce an idle surge that could stall the engine. |
| • | A stuck throttle position sensor may set a DTC P0742. |
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 D4 to achieve FOURTH gear under steady acceleration, with
the 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
|
- Inspect the transmission for the following conditions:
| • | TCC PWM solenoid valve for a damaged exhaust orifice |
| • | TCC shift valve for being stuck |
| • | Converter regulated apply valve stuck in the released position |
| • | Restricted apply or release passage |
| • | Misaligned or damaged valve body gasket |
| • | Torque converter mechanically stuck ON |
- 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
|
