4T65-E Automatic Transaxle
DTC P1823
Circuit Description
The transmission internal mode switch (IMS) is a sliding contact switch attached to the selector detent inside the transmission side cover. The four inputs to the PCM indicate the position of the transmission range selector. The input voltage level at the PCM is high, B+, when the IMS is open and low when the switch is closed to ground. The four input parameters represented are Signals A, B, C and P - Parity. Refer to Transmission Internal Mode Switch Logic.
If the PCM detects that IMS Signal P is always low, then DTC P1823 sets. DTC P1823 is a type C 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 MAP DTC P0107 or P0108.
* The engine speed is greater than 500 RPM for 5 seconds and not in fuel cut off.
* Engine torque is 55-407 N.m (40-300 lb ft).
Conditions for Setting the DTC
The IMS Signal P is continuously low this ignition cycle, and the following conditions occur:
* The IMS indicates PARK for 2 seconds, then;
* The IMS indicates transitional position N-D4 for 60 seconds.
Action Taken When the DTC Sets
* The PCM does not illuminate the malfunction indicator lamp (MIL).
* The PCM commands maximum line pressure.
* The PCM freezes transmission adaptive functions.
* The PCM assumes D4 for shifting.
* The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Failure Records.
* The PCM stores DTC P1823 in PCM history.
Conditions for Clearing the DTC
* A scan tool can clear the DTC.
* The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without a non-emission-related diagnostic fault occurring.
* The PCM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the PCM.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
3. A LOW signal indicates a short to ground in the vehicle harness or the PCM.
5. This step tests the internal transmission harness without the IMS connected.
