P1890

Schematic:

Circuit Description with 4L30-E Automatic Transmission
The Engine Control Module (ECM) sends the transmission control module (TCM) throttle position and throttle angle signal through a communication network called the Controller Area Network (CAN). Circuits XR888 and XY888 are used to communicate CAN data between the ECM and TCM control modules.

When the TCM detects the ECM throttle signal is unreliable, then DTC P1890 will set. DTC P1890 is a type B DTC.

CONDITION FOR RUNNING THE DTC
The ignition switch is in the RUN position.

CONDITION FOR SETTING THE DTC
The throttle position or throttle angle signal is an unreliable value for 1 second.

ACTION TAKEN WHEN THE DTC SETS
^ The TCM flashes the sport mode lamp and sends a MIL request to the ECM on the second consecutive drive trip that the diagnostic runs and fails. The ECM then illuminates the MIL.
^ The ECM records the operating conditions in the Freeze Frame at the time of the MIL request from the TCM.
^ The transmission operates in the default mode (maximum line pressure, command 4th gear, inhibit TCC, freeze shift adapts).

Diagnostic Chart:

CONDITIONS FOR CLEARING THE MIL/DTC
^ The ECM turns off the MIL after three consecutive drive trips during which the TCM sends no MIL request.
^ A History DTC clears after forty consecutive warm-up cycles, if no failures are present by this diagnostic or any other emission related diagnostic.
^ The scan tool clears the MIL/DTC.
^ The TCM cancels the DTC default mode actions when the ignition switch is Off long enough in order to power down the TCM.

DIAGNOSTIC AIDS
Use the J 35616-A connector test adapter kit for any test that requires probing the TCM harness connector or a component harness connector. Using this kit will prevent damage to the harness connector terminals.

Check for the following conditions:
^ Poor connections at the TCM or at the component. Inspect the harness connectors for any backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.
Refer to General Electrical Diagnosis Procedures in Diagrams for proper procedure.
^ Damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the scan tool while moving any related connectors and any wiring harnesses. A change in the display may help to locate the fault.