P1875

DTC P1875 4 Wheel Drive Switch Circuit:

4 Wheel Drive Switch Circuit:

CIRCUIT DESCRIPTION

The Transmission Control Module (TCM) determines when the vehicle's transfer case is set in 4L position through the 4L switch. The 4L switch closes then the transfer case is set in 4L. The 4L switch, when closed, ground the circuit to the TCM. The TCM uses this information to prevent Torque Converter Clutch (TCC) lock-up and prevent 4th gear from engaging.


DTC DETECTING CONDITIONS

While driving at higher than 5 km/h vehicle speed and more than 5% throttle valve opening, following conditions are satisfied for 20 seconds:

- Vehicle speed sensed by the Vehicle Speed Sensor (VSS) (Speedometer) is more than 10 km/h lower than sensed by the VSS (Transmission) when 4L switch is open.

- Or the vehicle speed sensed by the VSS (Speedometer) is more than 10 km/h higher than that sensed by the VSS (Transmission) when 4L switch is closed.

- Two driving cycle detection logic.

ACTION TAKEN

A DTC P1875 is stored and both the "OD/OFF" and "SERVICE ENGINE SOON" indicators are illuminated.


DTC CHART TEST DESCRIPTION

Numbers below refer to circled numbers on the diagnostic chart.

1. Checks the operation of the 4WD "LO" switch.

2. Checks for proper resistance values.

3. Checks for poor connector terminal contact that may have caused DTC to set.

4. Determines whether the condition is intermittent and not related to a faulty TCM.

5. Checks for a constantly-closed 4L switch or a short to ground in ORN/WHT wire.

6. Checks for a constantly-open 4L switch or an open in ORN/WHT wire.


DIAGNOSTIC AIDS

An intermittent condition may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Inspect the TCM harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals and for poor terminal-to-wire connections.