For 1990-2009 cars
Master Electrical Component List
Automatic Transmission Controls Schematics
OBD II Symbol Description Notice

### Circuit Description

The engine control module (ECM) transmits downshift requests to the transmission control module (TCM) when the accelerator pedal position exceeds 89 percent The ECM sends the downshift request to the TCM on a communication network called the controller area network (CAN). A fault in the CAN will not cause DTC P1835 to set by itself. If a CAN fault occurs, other DTCs will set before DTC P1835.

If the TCM detects a throttle angle lower than 89 percent and the ECM is requesting a downshift, then DTC P1835 sets. DTC P1835 is a type C DTC.

### Conditions for Running the DTC

• | The ignition is ON.

• | No Throttle Position Signal DTC P1890.

• | Throttle is less than 89 percent.

### Condition for Setting the DTC

ECM is sending a downshift request to the TCM.

### Action Taken When the DTC Sets

• | The TCM does not request the ECM to illuminate the MIL.

• | The ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM records this information as Failure Records.

• | The TCM stores DTC P1835 in TCM history.

• | The TCM will enable downshifts when the throttle reaches its limit.

### Conditions for Clearing the DTC

• | A scan tool can clear the DTC.

• | The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without a non-emission-related diagnostic fault occurring.

• | The TCM cancels the DTC default mode actions when the fault no longer exists.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform Powertrain On Board Diagnostic (OBD) System Check - Automatic Transmission ? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check - Automatic Transmission
2 |

1. Install the Scan Tool .
2. Turn ON the ignition, with the engine OFF.

Important: Record all Failure Records before clearing the DTC. Using Clear Info erases the Failure Records from the ECM and TCM.

3. Record the DTC Failure Records.

Did you record any ECM Failure Records?

--

Go to the applicable ECM DTC

Go to Step 3

3 | Did you record Failure Records for any of the following DTCs?

• | DTC U2100

• | DTC U2104

• | DTC U2105

• | DTC U2108

--

Go to the applicable CAN Bus DTC

Go to Step 4

4 |

1. Clear the DTC.
2. Turn OFF the ignition for at least 30 seconds.
3. Start and idle the engine.
4. Observe the WOT Switch value on the scan tool.

Does the display indicate that the WOT switch is OFF?

--

Go to Step 5

Go to Step 6

5 | Road test the vehicle for at least five minutes, applying the accelerator pedal in order to command a downshift. Refer to Shift Speed . Did DTC P1835 reset? | -- | Go to Step 6 | Go to Intermittent Conditions in Engine Controls
6 | Did any other DTCs set? | -- | Go to the applicable DTC | Go to Step 7
7 | Replace the ECM. Refer to Engine Control Module Replacement . Is the action complete? | -- | Go to Step 9 | --
8 | Perform the following operation to verify the repair:

1. Select DTC on the scan tool.
2. Select Clear Info.
3. Road test the vehicle for at least five minutes, applying the accelerator pedal in order to command a downshift. Refer to Shift Speed .

Did DTC P1835 reset?

--

Go to Step 1

System OK