GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2004 🢒 Aveo 🢒 DTC 🢒 DTC P0743

DTC P0743 Non Europe or N. American Emissions

Conditions for Setting the DTC
    • The transmission control module (TCM) detects that the ON signal of the lockup solenoid monitor during 0.5 seconds when lockup solenoid driver outputs the OFF signal. The torque converter clutch (TCC) circuit is open or short to battery.
    • The TCM detects that the OFF signal of the lockup solenoid monitor during 0.3 seconds when lockup solenoid driver outputs the ON signal. The TCC circuit is short to battery.
    • The above detection 8 times at shifting continuously

Action Taken When the DTC Sets
    • TCM will request the illumination of the hold lamp and store the DTC when the TCM detects failures on 2 consecutive ignition cycles
    • No TCC lockup solenoid
    • 1st gear fixed under the 10 km/h

Conditions for Clearing the DTC
    • The TCM turns off the hold lamp when no further failures are detected on the next ignition cycles.
    • The scan tool can clear the DTC from the TCM history.
    • The TCM clears the DTC from the TCM history memory after 40 consecutive ignition cycles without fault.
    • The TCM detects the ON signal of the lockup solenoid monitor during 160 ms when the lockup solenoid driver outputs the ON signal and the TCM detects the OFF signal of the lockup solenoid monitor during 160 ms when lockup solenoid driver outputs the OFF signal.

Cause of Failure
    • Wiring harness or connector between lockup solenoid and TCM
    • Lockup solenoid
    • TCM

Step

Action

Values

Yes

No

1
  1. Turn OFF the ignition.
  2. Install the scan tool.
  3. With the engine OFF, turn the ignition switch to the ON position.
  4. Select Store Freeze Frame/Failure Records from the Diagnostic Trouble Codes Information menu.
  5. Store Freeze Frame/Failure Records.
  6. Select Clear DTC Information from the Diagnostic Trouble Codes Information menu.
  7. Clear DTC Information.
  8. Perform 2 vehicle drive cycles.

Is the hold lamp ON?

--

Go to Step 2

Go to Step 4

2
  1. Select Request DTC by Status from the Diagnostic Trouble Codes Information menu.
  2. Request DTC by Status.

Is DTC P0743 displayed?

--

Go to Step 3

Go to Step 5

3
  1. Turn OFF the ignition.
  2. Measure the resistance between the vehicle harness and lock-up solenoid. Refer to 1, 2 Shift Solenoid, Timing Solenoid, and Lock-Up Solenoid Inspection .
  3. Disconnect the transmission control module (TCM) connector and measure the resistance between the terminal A5 and A23.

Is the measurement within the specified values?

20°C (68°F)

11-16 ohms

Go to Step 5

Go to Step 6

4

Repair the temporary connection failure of the connector. Refer to Wiring Harness and Connector Inspection Diagnosis .

Did you complete the repair?

--

System OK

--

5
  1. Estimate the failure of between the vehicle wiring harness connector and TCM.
  2. Inspect the connector. Refer to Wiring Harness and Connector Inspection Diagnosis .
  3. Inspect the connection condition between the connectors.

Is the connection condition OK?

--

Go to Step 7

Go to Step 4

6
  1. Estimate the failure of between the vehicle harness and lockup solenoid.
  2. Disconnect the transaxle harness connector and measure the resistance between lock-up solenoid connector terminal 4 and ground.

Is the measurement within the specified values?

20°C (68°F)

11-16 ohms

Go to Step 8

Go to Step 9

7
  1. Replace the TCM.
  2. Perform the reproducing test under user condition after confirming no DTC.

Is DTC displayed?

--

Go to Step 1

System OK

8
  1. Estimate the failure of the vehicle wiring harness or between connectors.
  2. Test continuity and short circuit for the vehicle wiring harness and inspect the connection condition between connectors. Refer to Wiring Harness and Connector Inspection Diagnosis .

Is the condition OK?

--

Go to Step 4

Go to Step 11

9
  1. Estimate the failure of the transaxle harness or between connectors of lockup solenoid.
  2. Inspect the lockup solenoid. Refer to 1, 2 Shift Solenoid, Timing Solenoid, and Lock-Up Solenoid Inspection .

Is the problem found?

--

Go to Step 12

Go to Step 10

10
  1. Estimate the failure of the transaxle harness.
  2. Test continuity and short circuit for the transaxle harness and inspect the connection condition between connectors. Refer to Wiring Harness and Connector Inspection Diagnosis .

Is the condition OK?

--

Go to Step 4

Go to Step 11

11

Replace the transaxle harness.

Did you complete the replacement?

--

System OK

--

12

Replace the lock-up solenoid. Refer to 1, 2 Shift Solenoid, Timing Solenoid, and Lock-Up Solenoid Inspection .

Did you complete the replacement?

--

System OK

--

DTC P0743 European and N. American Emissions

Conditions for Setting the DTC
    • The transmission control module (TCM) detects that the ON signal of the lockup solenoid monitor during 0.5 seconds when lockup solenoid driver outputs the OFF signal. The torque converter clutch (TCC) circuit is open or short to battery.
    • The TCM detects that the OFF signal of the lockup solenoid monitor during 0.3 seconds when lockup solenoid driver outputs the ON signal. The TCC circuit is short to battery.
    • The above detection 8 times at shifting continuously

Action Taken When the DTC Sets
    • TCM will request the illumination of the MIL lamp and store the DTC when the TCM detects failures on 2 consecutive ignition cycles
    • No TCC lockup solenoid
    • 1st gear fixed under the 10 km/h

Conditions for Clearing the DTC
    • The TCM turns off the MIL lamp when no further failures are detected on the next ignition cycles.
    • The scan tool can clear the DTC from the TCM history.
    • The TCM clears the DTC from the TCM history memory after 40 consecutive ignition cycles without fault.
    • The TCM detects the ON signal of the lockup solenoid monitor during 160 ms when the lockup solenoid driver outputs the ON signal and the TCM detects the OFF signal of the lockup solenoid monitor during 160 ms when lockup solenoid driver outputs the OFF signal.

Cause of Failure
    • Wiring harness or connector between lockup solenoid and TCM
    • Lockup solenoid
    • TCM

Step

Action

Values

Yes

No

1
  1. Turn OFF the ignition.
  2. Install the scan tool.
  3. With the engine OFF, turn the ignition switch to the ON position.
  4. Select Store Freeze Frame/Failure Records from the Diagnostic Trouble Codes Information menu.
  5. Store Freeze Frame/Failure Records.
  6. Select Clear DTC Information from the Diagnostic Trouble Codes Information menu.
  7. Clear DTC Information.
  8. Perform 2 vehicle drive cycles.

Is the MIL lamp ON?

--

Go to Step 2

Go to Step 4

2
  1. Select Request DTC by Status from the Diagnostic Trouble Codes Information menu.
  2. Request DTC by Status.

Is DTC P0743 displayed?

--

Go to Step 3

Go to Step 5

3
  1. Turn OFF the ignition.
  2. Measure the resistance between the vehicle harness and lock-up solenoid. Refer to 1, 2 Shift Solenoid, Timing Solenoid, and Lock-Up Solenoid Inspection .
  3. Disconnect the transmission control module (TCM) connector and measure the resistance between the terminal A5 and A23.

Is the measurement within the specified values?

20°C (68°F)

11-16 ohms

Go to Step 5

Go to Step 6

4

Repair the temporary connection failure of the connector. Refer to Wiring Harness and Connector Inspection Diagnosis .

Did you complete the repair?

--

System OK

--

5
  1. Estimate the failure of between the vehicle wiring harness connector and TCM.
  2. Inspect the connector. Refer to Wiring Harness and Connector Inspection Diagnosis .
  3. Inspect the connection condition between the connectors.

Is the connection condition OK?

--

Go to Step 7

Go to Step 4

6
  1. Estimate the failure of between the vehicle harness and lockup solenoid.
  2. Disconnect the transaxle harness connector and measure the resistance between lock-up solenoid connector terminal 4 and ground.

Is the measurement within the specified values?

20°C (68°F)

11-16 ohms

Go to Step 8

Go to Step 9

7
  1. Replace the TCM.
  2. Perform the reproducing test under user condition after confirming no DTC.

Is DTC displayed?

--

Go to Step 1

System OK

8
  1. Estimate the failure of the vehicle wiring harness or between connectors.
  2. Test continuity and short circuit for the vehicle wiring harness and inspect the connection condition between connectors. Refer to Wiring Harness and Connector Inspection Diagnosis .

Is the condition OK?

--

Go to Step 4

Go to Step 11

9
  1. Estimate the failure of the transaxle harness or between connectors of lockup solenoid.
  2. Inspect the lockup solenoid. Refer to 1, 2 Shift Solenoid, Timing Solenoid, and Lock-Up Solenoid Inspection .

Is the problem found?

--

Go to Step 12

Go to Step 10

10
  1. Estimate the failure of the transaxle harness.
  2. Test continuity and short circuit for the transaxle harness and inspect the connection condition between connectors. Refer to Wiring Harness and Connector Inspection Diagnosis .

Is the condition OK?

--

Go to Step 4

Go to Step 11

11

Replace the transaxle harness.

Did you complete the replacement?

--

System OK

--

12

Replace the lock-up solenoid. Refer to 1, 2 Shift Solenoid, Timing Solenoid, and Lock-Up Solenoid Inspection .

Did you complete the replacement?

--

System OK

--