4T65-E Automatic Transaxle
DTC P1826
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 C is high while the vehicle is being driven in a forward gear, then DTC P1826 sets. DTC P1826 is a type C DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1826 Internal Mode Switch C Circuit High Voltage
Conditions for Running the DTC
* No VSS DTCs P0502 or P0503.
* Vehicle speed is 16 km/h (10 mph) or greater.
* Engine torque is 27 N.m (20 lb ft) or greater.
* DTC P1826 has not passed this key cycle.
Conditions for Setting the DTC
The PCM detects IMS Signal C is high, while the gear ratio indicates first, second, third or fourth gear 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 P1826 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 number below refers to the step number on the diagnostic table.
3. This step tests the integrity of the engine harness and PCM by checking for the Signal C state change from HI to LOW. A LOW signal indicates the fault is either in the internal transmission harness or the switch. A HI signal indicates the fault is either in the engine harness or the PCM.
