Circuit Description
The special feature of the 4 HP 16 automatic transaxle is that it 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 a more compact design and is lighter on account of the absence of freewheels and the lower number of shift elements. |
| • | Lower drag losses, i.e. higher efficiency |
| • | Lower peak torque acting on the components and driveline |
However, overlap shifting necessitates high-performance hardware and software, and precision engine signals.
Conditions for Setting the DTC
| • | The transmission oil temperature is greater than -10°C (+14°F). |
| • | The selector lever is not in the neutral (N) or park (P) position. |
| • | The system voltage is greater than 9 volts. |
| • | No input speed error DTCs P0715, P0716, or P0717 are set. |
| • | The output speed is greater than 256 RPM. |
| • | The input speed is greater than 400 RPM. |
| • | The 2-1 gear shift is active. |
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 3rd gear. |
| • | Open lock up clutch |
Conditions for Clearing the MIL/DTC
| • | The MIL 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 P1881 sets, the possible cause of the fault could be the TCM.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Automatic Transmission? | -- | Go to Step 2 | |
2 |
Was a condition found? | -- | Go to Diagnostic System Check - Engine Controls in Engine Controls | Go to Step 3 |
3 | Inspect the electronic control module (ECM). Was a condition found? | -- | Go to Engine Control Module Replacement in Engine Controls | Go to Step 4 |
4 |
Is the voltage within the specified values? | 11-14 V | Go to Step 5 | |
5 | Replace the TCM. Refer to Transmission Control Module Replacement . Did you complete the replacement? | -- | Go to Step 6 | -- |
6 |
Has the last test failed or is the current DTC displayed? | -- | Go to Step 7 | System OK |
7 | Replace the transaxle assembly. Refer to Transmission Replacement . Did you complete the replacement? | -- | Go to Step 8 | -- |
8 |
Are there any DTCs displayed that have not been diagnosed? | -- | Go to Step 2 | System OK |
