P1884

VT25-E AUTOMATIC TRANSMISSION

DTC P1884

Test 1-7:

Test 8-18:

Test 19-22:

Circuit Description with VT25-E Automatic Transmission
The transmission control module (TCM) uses the ratio control motor to control the speed ratio. The ratio control motor is a linear position device, which changes the speed ratio by accurately controlling the position of the variable ratio control valve. Movement of the variable ratio control valve allows fluid to be applied and exhausted from the primary feed limit circuit. The TCM controls the ratio control motor by grounding four control circuits with power being supplied directly from the fuse block - underhood. The TCM monitors the status of the four low control circuits and can detect a short to power or a short to ground/open.

When either of these failures is detected, DTC P1884 sets. DTC P1884 is a type A DTC.

Conditions for Running the DTC
The engine speed is greater than 500 RPM for 5 seconds.

Conditions for Setting the DTC
The TCM detects an open, a short to ground, or a short to voltage on the ratio control motor A2 control circuit for 0.56 seconds.

Action Taken When the DTC Sets
^ The TCM requests the ECM to illuminate the malfunction indicator lamp (MIL).
^ The TCM moves the speed ratio towards a target ratio and then freezes ratio changes.
^ The TCM discontinues use of the closed loop ratio control algorithm. This causes the speed ratio to be defaulted and possibly not accurate. The resulting open loop control may or may not provide optimum ratio performance.
^ The ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM stores this information as Freeze Frame and Failure Records.
^ The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as Failure Records.
^ The TCM stores DTC P1884 in TCM history.

Conditions for Clearing the MIL/DTC
^ The ECM turns OFF the MIL after the third consecutive drive trip in which the TCM does not send a MIL illumination request.
^ A scan tool can clear the MIL/DTC.
^ The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
^ The TCM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the TCM.

Diagnostic Aids
^ Inspect the connectors at the TCM, the transmission, and all other circuit connecting points for an intermittent condition.
^ Inspect the circuit wiring for an intermittent condition.