P1823
DTC P1823
Circuit Description
The transmission manual shift shaft switch assembly is a sliding contact switch attached to the control valve body within the transmission. The 4 inputs to the transmission control module (TCM) from the switch indicate which position is selected by the transmission selector lever. This information is used for engine controls as well as determining the transmission shift patterns. The input voltage at the TCM is high when the switch is open and low when the switch is closed to ground. The state of each input is displayed on the scan tool as IMS. The 4 IMS input parameters represented are Signal A, Signal B, Signal C and Signal P (Parity).
If the TCM detects a short to ground on the TR signal P circuit, DTC P1823 sets. DTC P1823 is a type B DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1823 Internal Mode Switch P Circuit Low Voltage
Conditions for Running the DTC
* No engine torque signal DTC P2637.
* The engine run time is greater than 5 seconds.
* The engine torque is greater than 55 N.m (41 lb ft).
Conditions for Setting the DTC
* The switch indicates PARK for 1 second, then;
* The switch indicates a transitional state between Neutral and D5 for 5 seconds.
Action Taken When the DTC Sets
* The TCM requests the ECM to illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met.
* The TCM commands maximum line pressure.
* The TCM freezes transmission adaptive functions.
* The TCM assumes a D5 shift pattern.
* At the time of the first failure, the TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as a Failure Record.
* At the time of the second failure, the ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM stores this information as a Freeze Frame.
* The TCM stores DTC P1823 in TCM history.
Conditions for Clearing the DTC
* The ECM turns OFF the MIL after the sixth consecutive drive trip in which the TCM does not send a MIL illumination request.
* 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 actions when the ignition is OFF long enough in order to power down the TCM.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
3. This step determines if the fault is internal or external to the transmission.
4. This step determines if the engine wiring harness circuit or the TCM is at fault.
5. This step determines if the automatic transmission wiring harness or the transmission manual shift shaft switch assembly is at fault.
