For 1990-2009 cars

### Circuit Description

When the transfer case is shifted into the 4L position, the 4L switch closes. When the 4L switch closes, the 4L switch grounds the circuit to the powertrain control module (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

The PCM uses the vehicle speed sensor (VSS) 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. DTC P1875 sets if the following condition occurs:

• | The VSS senses a vehicle speed of more than 10 km/h (6 mph) lower than the output shaft speed.

• | 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.

Refer to Wiring Repairs in Wiring Systems when repairing any wiring.

### 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

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. Shift the manual selector to DRIVE range.
13. Accelerate the vehicle in DRIVE range.

Continue driving for 10 seconds at 30 km/h (19 mph).

14. Stop the vehicle.
15. 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 test for a short to ground condition.

3. This step test for an open condition.

4. This step inspects for a faulty PCM.

Step | Action | Yes | No
--- | --- | --- | ---
Schematic Reference: Automatic Transmission Controls Schematics
1 | Was the On-Board Diagnostic (OBD) System Check performed? | Go to Step 2 | Go to Diagnostic System Check - Engine Controls in Engine Controls-2.5 L
2 |

1. Install a scan tool.
2. Turn the ignition to ON, Leaving the engine OFF.
3. Perform the scan tool Clear DTC information.
4. Operate the vehicle within the Freeze Frame conditions as observed.
5. Place the transmission in NEUTRAL.
6. Select 2H range on the transfer case selector.

Does the scan tool 4WD Low display Disabled when you select 2H range and then Enabled when you select 4L range?

Go to Step 3

Go to Step 4

3 |

1. Turn the ignition to OFF.
2. Disconnect the 4L range switch connector.
3. Turn the ignition to ON, leaving the engine OFF.

Does the scan tool indicate 4WD Enabled?

Go to Step 4

Go to Step 6

4 |

1. Test the ORN/WHT wire for a short to ground condition. Refer to General Electrical Diagnosis in Wiring Systems.
2. Repair the ORN/WHT wire if necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct a short to ground condition?

Go to Step 8

Go to Step 5

5 |

1. Test the ORN/WHT wire for an open condition. Refer to General Electrical Diagnosis in Wiring Systems.
2. Repair the ORN/WHT wire if necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct an open condition?

Go to Step 8

Go to Step 6

6 |

1. Install a known-good PCM.
2. Perform the DTC Confirmation Procedure.

Does the DTC1875 reset?

Go to Step 7

Go to Diagnostic Aids

7 |

1. Replace the powertrain control module (PCM).
2. Refer to Powertrain Control Module Replacement in Engine Controls-2.0L or Powertrain Control Module Replacement in Engine Controls-2.5L.

Is the procedure complete?

Go to Step 8

--

8 |

1. Select the DTC.
2. Select Clear Information.
3. Operate the vehicle under the following conditions:

3.1. | Select the 4L range on the transfer case selector.

3.2. | Drive the vehicle in 4WD.

3.3. | Select 2H or 4H on the transfer case selector.

3.4. | Drive the vehicle in 4WD with the TCC on.

Has the test run and passed?

System OK

Go to Step 1