Circuit Description
Transmission down-shift request is sent to the transmission control module (TCM) by the engine control module (ECM) through a communication network called controller area network (CAN). Circuits XR888 and XY888 are used to communicate CAN data between the ECM and TCM control modules. When the ECM senses high throttle demand greater than 89%, lower transmission output speeds for this demand, and certain commanded gear limits, the ECM will signal the transmission for a down-shift to a lower gear (Kick-down).
When the TCM detects a throttle angle lower than 89% and the ECM is requesting Kick-down, then DTC P1835 will set. DTC P1835 is a type D DTC.
Conditions for Running the DTC
| • | The ignition switch is in the RUN position. |
| • | No Throttle Position Signal DTC P1890. |
| • | Throttle is less than 89%. |
Condition for Setting the DTC
ECM is sending a Kick-down request signal to the TCM.
Action Taken When the DTC Sets
| • | The ECM records the operating conditions in the Failure Records at the time of the request from the TCM. |
| • | The TCM will enable kick-down with throttle limits. |
Conditions for Clearing the DTC
| • | A history DTC clears after forty consecutive warm-up cycles, if no failures are present by this diagnostic or any other emission related diagnostic. |
| • | The scan tool clears the DTC. |
| • | The TCM cancels the DTC default mode actions when the fault no longer exists and the ignition switch is OFF long enough in order to power down the TCM. |
Diagnostic Aids
Turn the ignition switch to the RUN positions and operate the throttle at a closed position and then at wide open position. Watch the scan tool WOT switch displays to see if the display reads NO below 89% throttle position and YES when the throttle is above 89%.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step verifies the kick-down request is present.
-
This step checks for engine DTCs that would normally set if engine throttle conditions were detected.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||
Important: Before clearing the DTC, use the Scan Tool in order to record the Failure Records. Using the Clear Info function erases the Failure Records from the ECM/TCM. Does the WOT switch display OFF? | -- | Go to Diagnostic Aids | ||
|
Does the WOT switch display ON? | -- | -- | ||
4 | Does the engine torque display a high torque value with transmission in D4 and the engine idling? | -- | -- | |
5 | Check for any ECM DTCs. Are there ECM DTCs present? | -- | -- | |
6 | Go to the appropriate ECM DTC. Make the necessary repairs. Refer to Engine Controls Are the DTC repairs complete? | -- | Go to Engine Controls | |
7 | Perform the following procedure in order to verify the repair:
Does the Scan Tool WOT switch display NO and is DTC P1835 not present? | -- | System OK |
