P1875

Circuit Description
The Powertrain Control Module (PCM) determines when the 4L switch sets the vehicle's transfer case into 4L position. The transfer case sets into 4L position when the 4L switch closes. When the 4L switch closes, the 4L switch grounds the circuit to the PCM connector C3 terminal 3. The PCM uses the above information in order to prevent Torque Converter Clutch (TCC) lock-up and 4th gear engagement.

Conditions for Setting the DTC
DTC P1875 sets if one of the following conditions occur for 20 seconds when driving at higher than 5 km/h vehicle speed and more than 5% throttle valve opening.
^ The Vehicle Speed Sensor (VSS) (Speedometer) senses a vehicle speed of more than 10 km/h lower than the vehicle speed the VSS (Transmission) senses.
^ The Vehicle Speed Sensor (VSS) (Speedometer) senses a vehicle speed of more than 10 km/h higher than the vehicle speed the VSS (Transmission) senses.
^ Two driving cycle detection logic.

Action Taken When the DTC Sets
^ DTC P1875 stores.
^ The Malfunction Indicator Lamp (MIL) turns ON.

Diagnostic Aids
Inspect for the following conditions:
^ A faulty 4L switch
^ Faulty electrical circuits between the 4L switch and the PCM
^ A faulty PCM
The following conditions may cause an intermittent:
^ A reduced connection
^ Rubbed through wire insulation
^ A broken wire inside the insulation
Inspect the PCM harness connectors for the following conditions:
^ Backed out terminals
^ Improper mating
^ Broken locks
^ Improperly formed or damaged terminals
^ Reduced terminal-to-wire connections

If DTC P1875 cannot duplicate, the information included in the Freeze Frame data may be useful in determining the vehicle operating conditions when the DTC set.

DTC Confirmation Procedure
1. Turn the ignition switch to the LOCK position.
2. Connect the Scan Tool to the Data Link Connector (DLC).
3. Turn the ignition switch ON.
4. Use the Scan Tool in order to clear the following items:
^ DTC P1875
^ Any pending DTCs
^ The freeze frame data in the PCM memory.
5. Start the engine.
6. Apply the brake pedal firmly
7. Shift the manual selector to DRIVE range. Remain in the DRIVE range for 30 seconds.
8. Accelerate the vehicle in DRIVE range. Continue driving for 10 seconds at 30 km/h (19 mph).
9. Stop the vehicle.
10. Shift the manual selector to the PARK range.
11. Shift the transfer case lever to the 4L range.
12. Accelerate the vehicle in PARK range. Continue driving for 10 seconds at 30 km/h (19 mph).
13. Stop the vehicle.
14. Use the Scan Tool in order to test for a pending DTC.

Test Description
The numbers below refer to the step numbers on the diagnostic table.
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. The Scan Tool creates an electronic copy of the data taken when the fault occurred. The information then stores in the scan tool for later reference.
2. This step tests the circuit output of the 4L signal circuit to the PCM.
3. This step tests for one of the following conditions:
^ A short to ground in the 4L signal circuit
^ A faulty 4L switch.
Refer to the above figure.
4. This step verifies that the 4L switch closes when a transfer case sets in 4L.
This action grounds the 4L signal circuit.
5. This step determines if the 4L switch is closed.
6. This step tests the ground circuit to the 4L switch.
7. This step tests the integrity of the 4L signal circuit.
8. This step tests the integrity of the 4L switch by cycling.
10. This step determines if the following conditions exist:
^ The PCM is faulty.
^ The malfunction is intermittent.
15. The transfer case appears to have a mechanical problem not causing the 4L to close when set in 4L range.
16. The PCM uses the Vehicle Speed Sensor (VSS) (Transmission) and the VSS (Speedometer) in order to trigger DTC P1875. Vehicle speed differences between the above components trigger DTC P1875. If the VSS Transmission does not function as designed, the transmission may set DTC P1875. The above action may occur even when the 4L signal circuit is both mechanically and electrically in good condition.