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.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
2 |
Did you find and correct the condition? | -- | Go to Step 6 | Go to Step 3 |
3 | Inspect the engine control module (ECM). Refer to Symptoms - Computer/Integrating Systems Did you find and correct the condition? | -- | Go to Step 6 | Go to Step 4 |
4 |
Is the voltage within the specified value? | 11-14 V | Go to Step 5 | |
5 | Replace the TCM. Refer to Transmission Control Module Replacement . Is the action complete? | -- | Go to Step 6 | -- |
6 |
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 |
Has the last test failed or is the current DTC displayed? | -- | Go to Step 2 | System OK |
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.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
2 |
Did you find and correct the condition? | -- | Go to Step 6 | Go to Step 3 |
3 | Inspect the ECM. Refer to Symptoms - Computer/Integrating Systems . Did you find and correct the condition? | -- | Go to Step 6 | Go to Step 4 |
4 |
Is the voltage within the specified value? | 11-14 V | Go to Step 5 | |
5 | Replace the TCM. Refer to Transmission Control Module Replacement . Is the action complete? | -- | Go to Step 6 | -- |
6 |
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 |
Has the last test failed or is the current DTC displayed? | -- | Go to Step 2 | System OK |
