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For 1990-2009 cars only

DTC P0781 European and N. American Emissions

Circuit Description

The special feature of 4HP 16 Auto Transaxle is that the transaxle operates without freewheels.

Shifting between individual gears takes place by means of overlapping clutch engagement and release.

The advantages of overlap shifting are as follows:

    • The transaxle can be of more compact design and is lighter because of the absence of freewheels and the lower number of shift elements.
    • Lower drag losses, such as higher efficiency
    • Lower peak torque acting on the components and the driveline

However, overlap shifting necessitates high-performance hardware and software, and precision engine signals.

Conditions for Setting the DTC

    • Transmission oil temperature is greater than -10°C (14°F).
    • The selector lever is not in the N (Neutral) or P (Park) position.
    • System voltage is greater than 9 volts.
    • No input speed error DTCs P0715, P0716, and P0717
    • Output speed is greater than 256 RPM.
    • Input speed is greater than 400 RPM.
    • 1-2 gear shift is active.
    • Immediately after the above condition occurs

Action Taken When the DTC Sets

    • The malfunction indicator lamp (MIL) will illuminate.
    • The transmission control module (TCM) will record operating conditions at the time the diagnostic fails. This information will be stored in the Failure Records buffer.
    • Adopt Emergency/Substitute mode and constant 1st gear.
    • Open lock up clutch

Conditions for Clearing the MIL/DTC

    • The MIL will turn OFF when the malfunction has not occurred after 3 ignition cycles.
    • A history DTC will clear after 40 consecutive warm-up cycles without a fault.
    • Using a scan tool can clear history DTCs.

Diagnostic Aids

When DTC P0781 sets, the possible cause of fault could be the TCM.

DTC P0781

Step

Action

Values

Yes

No

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Install the scan tool.
  2. Turn the ignition ON, with the engine OFF.
  3. Start the engine. Allow the engine to warm at idle.
  4. Observe the Idle PM, TPS on the scan tool.

Did you find and correct the condition?

--

Go to Step 6

Go to Step 3

3

Inspect the engine control module (ECM). Refer to the following:

    •  Diagnostic Starting Point - Engine Controls for the 1.4L DOHC engine
    •  Diagnostic Starting Point - Engine Controls for the 1.6L (L91) engine
    •  Diagnostic Starting Point - Engine Controls for the 1.8L (L79) engine
    •  Diagnostic Starting Point - Engine Controls for the 1.8L (LDA) engine
    •  Diagnostic Starting Point - Engine Controls for the 2.0L (GMDAT) engine

Did you find and correct the condition?

--

Go to Step 6

Go to Step 4

4

  1. Turn the ignition OFF.
  2. Disconnect the transmission control module (TCM) wiring connector.
  3. Measure the voltage between terminal B3 and B13 of the transaxle wiring connector.
  4. Turn the ignition ON, with the engine OFF.
  5. Measure the voltage between terminal C15 and B13 of the transaxle wiring connector.
  6. Measure the voltage between terminal C16 and B13 of the transaxle wiring connector.

Is the voltage within the specified value?

11-14 V

Go to Step 5

Go to DTC P0562 or to DTC P0563

5

Replace the TCM. Refer to Transmission Control Module Replacement .

Is the action complete?

--

Go to Step 6

--

6

  1. After the repair, use a scan tool "clear info" function.
  2. Road test the vehicle.
  3. Review the DTC info.

Has the last test failed or is the current DTC displayed?

--

Go to Step 7

System OK

7

Repair or replace the transaxle assembly. Refer to Transmission Replacement .

Did you complete the action?

--

Go to Step 8

--

8

  1. After the repair, use a scan tool "clear info" function.
  2. Road test the vehicle.
  3. Review the DTC info.

Has the last test failed or is the current DTC displayed?

--

Go to Step 2

System OK

DTC P0781 Non-European or N. American Emissions

Circuit Description

The special feature of 4HP 16 Auto Transaxle is that the transaxle operates without freewheels.

Shifting between individual gears takes place by means of overlapping clutch engagement and release.

The advantages of overlap shifting are as follows:

    • The transaxle can be of more compact design and is lighter because of the absence of freewheels and the lower number of shift elements.
    • Lower drag losses, such as higher efficiency
    • Lower peak torque acting on the components and the driveline

However, overlap shifting necessitates high-performance hardware and software, and precision engine signals.

Conditions for Setting the DTC

    • Transmission oil temperature is greater than --10°C (14°F).
    • The selector lever is not in the N (Neutral) or P (Park) position.
    • System voltage is greater than 9 volts.
    • No input speed error DTCs P0715, P0716, and P0717
    • Output speed is greater than 256 RPM.
    • Input speed is greater than 400 RPM.
    • 1-2 gear shift is active.
    • Immediately after the above condition occurs

Action Taken When the DTC Sets

    • The hold lamp will blink.
    • The transmission control module (TCM) will record operating conditions at the time the diagnostic fails. This information will be stored in the Failure Records buffer.
    • Adopt Emergency/Substitute mode and constant 1st gear.
    • Open lock up clutch

Conditions for Clearing the Hold Lamp/DTC

    • The hold lamp will turn OFF when the malfunction has not occurred after 3 ignition cycles.
    • A history DTC will clear after 40 consecutive warm-up cycles without a fault.
    • Using a scan tool can clear history DTCs.

Diagnostic Aids

When DTC P0781 sets, the possible cause of fault could be the TCM.

DTC P0781

Step

Action

Values

Yes

No

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Install the scan tool.
  2. Turn the ignition ON, with the engine OFF.
  3. Start the engine. Allow the engine to warm at idle.
  4. Observe the Idle PM, TPS on the scan tool.

Did you find and correct the condition?

--

Go to Step 6

Go to Step 3

3

Inspect the engine control module (ECM). Refer to the following:

    •  Diagnostic Starting Point - Engine Controls for the 1.4L DOHC engine
    •  Diagnostic Starting Point - Engine Controls for the 1.6L (L91) engine
    •  Diagnostic Starting Point - Engine Controls for the 1.8L (L79) engine
    •  Diagnostic Starting Point - Engine Controls for the 1.8L (LDA) engine
    •  Diagnostic Starting Point - Engine Controls for the 2.0L (GMDAT) engine

Did you find and correct the condition?

--

Go to Step 6

Go to Step 4

4

  1. Turn the ignition OFF.
  2. Disconnect the transmission control module (TCM) wiring connector.
  3. Measure the voltage between terminal B3 and B13 of the transaxle wiring connector.
  4. Turn the ignition ON, with the engine OFF.
  5. Measure the voltage between terminal C15 and B13 of the transaxle wiring connector.
  6. Measure the voltage between terminal C16 and B13 of the transaxle wiring connector.

Is the voltage within the specified value?

11-14 V

Go to Step 5

Go to DTC P0562 or to DTC P0563

5

Replace the TCM. Refer to Transmission Control Module Replacement .

Is the action complete?

--

Go to Step 6

--

6

  1. After the repair, use a scan tool "clear info" function.
  2. Road test the vehicle.
  3. Review the DTC info.

Has the last test failed or is the current DTC displayed?

--

Go to Step 7

System OK

7

Repair or replace the transaxle assembly. Refer to Transmission Replacement .

Did you complete the action?

--

Go to Step 8

--

8

  1. After the repair, use a scan tool "clear info" function.
  2. Road test the vehicle.
  3. Review the DTC info.

Has the last test failed or is the current DTC displayed?

--

Go to Step 2

System OK