P1890

Diagnostic Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION

This circuit provides several data parameters [e.g. ECT, Throttle Position (TP)] to the Transmission Control Module (TCM). The ECM pulls this circuit up to B+. The ECM induces a signal by toggling the B+ circuit to ground at a constant frequency of approximately 100 Hz. The TCM varies the duty cycle of this signal in order to transmit the data. The TCM interprets the variations in the duty cycle and separates out several encoded data parameters. The data transmission is one way, in a sequential order, a specific Pulse Width Modulated (PWM) signal represents each parameter value.

CONDITIONS FOR RUNNING THE DTC

Tests continuously

CONDITIONS FOR SETTING THE DTC

The TCM detects an open, short to ground, or short to B+ on the circuit.

ACTION TAKEN WHEN THE DTC SETS

^ The TCM illuminates the Service Transmission Lamp (STL) and sends a Malfunction Indicator Lamp (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.

CONDITIONS FOR CLEARING THE MIL/DTC

^ The TCM turns off the STL as soon as the fault is no longer present.

^ 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.

DIAGNOSTIC AIDS

Use the Connector Test Adapter Kit J 35616-A 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 Overall Vehicle Information / Diagrams / Diagnostic Aids for Checking Terminal Contact 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.

TEST DESCRIPTION

The number(s) below refer to the step number(s) on the Diagnostic Table.

2. The voltage may vary since this is a variable pulse width signal.