Code 31

This DTC flashes the CHECK TRANS indicator and sets the BACKUP MODE.

CIRCUIT DESCRIPTION:
The 1-2/3-4 solenoid is a simple ON/OFF solenoid located in the main case valve body. The solenoid is-the normally closed-type. In second or third gear the Transmission Control Module (TCM) energizes the solenoid to open a fluid inlet port. When the port is open, fluid pressure actuates the shift valve.
- The solenoid is activated by a current. This current is produced by applying a voltage to one side (the High side) and a ground to the other side (Low side).
- The High Side Driver (HSD) is a circuit of the TCM that acts as a switch between the solenoids and the supply voltage. The High side of the solenoid is permanently supplied with voltage, except in BACKUP MODE or when ignition is OFF the HSD is turned OFF.
- The TCM continually monitors the solenoid connection to its Low Side Driver (LSD) for either low or high voltage. The LSD is a circuit of the TCM that acts as a switch between the solenoid and ground. When the solenoid is commanded ON the TCM is switching the solenoid to ground.
- There are two tests of the LSD: When the engine is cranked (DTC82) and when the ignition is turned ON (DTC31).
- When the ignition is turned ON, and before the engine is cranked, the TCM activates the shift solenoids (1-2/3-4, 2-3 and Band) to check for short circuits or open circuits. To do so the gear is set to 4th, 3rd, 1st, 1st with band apply, 4th with no HSD. Each one of the 5 tests requires 0.15 second. If the engine is cranked before the end of all tests, the remaining tests are not done.

DIAGNOSTIC AIDS:
- This Diagnostic is an electrical test done by the TCM.
- Detection conditions:
- The solenoid low side connected to TCM terminal A2 is shorted to ground or open.
- The test is only done when ignition is ON.
- Engine Speed < 480 RPM (not cranked) and Output Speed = 0 RPM.
- The conditions need to be present for 0.15 to 1.03 second after ignition switch ON.
- Action after the detection time: BACKUP MODE.
- Recovery conditions: To recover, do an IGNITION CYCLE.