P1875

Diagnostic Chart:

Wiring Diagram:

Circuit Description

The Powertrain Control Module (PCM) 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 PCM C3 terminal 3. The PCM uses this information to prevent Torque Converter Clutch (TCC) lock-up and 4th gear engagement.

Conditions for Setting the DTC

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 When the DTC Sets

A DTC P1875 is stored and the Malfunction Indicator Lamp (MIL) indicator is illuminated.

Diagnostic Aids

Check for the following conditions:

- Faulty 4L switch.

- Faulty electrical circuits between the 4L switch and the PCM.

- Faulty PCM.

An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation.

Inspect the Powertrain Control Module (PCM) harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals and for poor terminal-to-wire connections.

If this DTC cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.

If any wiring repairs need to be made, refer to Repair Procedures in Electrical Diagnosis.

DTC Confirmation Procedure

1. Ignition switch to LOCK.

2. Connect scan tool to Data Link Connector (DLC).

3. Ignition switch to ON.

4. Clear DTC, pending DTC and freeze frame data in PCM memory by using scan tool.

5. Start engine.

6. Accelerate vehicle in Drive (D) range and keep driving for 30 seconds at about 30 km/h (19 mph).

7. Stop vehicle.

8. Shift manual selector to Park (P) range.

9. Shift transfer case lever to 4L range.

10. Accelerate vehicle in Drive (D) range and keep driving for 30 seconds at about 15 km/h (9 mph).

11. Stop vehicle.

12. Check for pending DTC with scan tool.

Test Description

Numbers below refer to circled numbers on the diagnostic chart.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

2. Checks the circuit output of the 4L signal circuit to the PCM.

Description:

3. Checks for either a short to ground in the 4L signal circuit or a faulty 4L switch (Image).

4. Checks that 4L switch closes (grounding 4L signal circuit) when transfer case is set in 4L.

5. Determines if 4L switch is in the close state.

6. Checks ground circuit to the 4L switch.

7. Checks the integrity of the 4L signal circuit.

8. Test the integrity of the 4L switch by cycling.

10. Determines whether the PCM is faulty or malfunction is intermittent.

15. The transfer case seems to have a mechanical problem not causing the 4L to close when set in 4L range.

16. The Vehicle Speed Sensor (VSS) (Transmission) is used by the PCM, in addition to the VSS (Speedometer), to trigger this DTC based on vehicle speed differences between the two VSS. If the VSS (Transmission) is not working as designed, it may cause this DTC to set, even though 4L signal circuit is both mechanically and electrically in good condition.