P1875

DTC P1875 4 Wheel Drive Switch Circuit (Diesel [1 Of 2]):

DTC P1875 4 Wheel Drive Switch Circuit (Diesel [2 Of 2]):

4 Wheel Drive Switch Circuit (Diesel):

CIRCUIT DESCRIPTION
When 4WD low engages, the input signal on circuit 1694 to the PCM will change from ignition voltage to zero. The 4WD low switch signal corrects the transmission output speed signal to the PCM. This signal compensates for transfer case gear reduction. The PCM uses the transmission output speed signal in order to adjust shift points, line pressure, and Torque Converter Clutch (TCC) scheduling.

When the PCM detects a continuous open or short to ground in the 4WD low circuit, then DTC P1875 sets. DTC P1875 is a type A DTC.

CONDITIONS FOR SETTING THE DTC

^ No Throttle Position (TP) Sensor DTC P0121, P0122 or P0123.
^ No Output Speed (OSS) Sensor DTCs P0722 or P0723.
^ No TCC Pulse Width Modulated Solenoid Valve (TCC PWM Sol. Valve) DTC P0742.
^ No 1-2 Shift Solenoid Valve (1-2 SS Valve) DTCs P0753 or P0751.
^ No 2-3 Shift Solenoid Valve (2-3 SS Valve) DTCs P0758 or P0756.
^ No Transmission Fluid Pressure Valve Position Switch (TFP Val. Position Sw.) DTC P1810.
^ No TCC PWM Sol. Valve DTC P1860.
^ The gear range is D4.
^ The TP angle is 9%-99%.
^ The engine is running for no greater than 5 seconds.
^ The Transmission Fluid Temperature (TFT) is 0°-130°C (32°-248°F).
^ The shift solenoid performance fail counters are zero.
^ All of the above conditions are met and one of the following fail conditions are true:

- Four wheel drive low is stuck ON for 3 seconds in two different gears, and the transfer case ratio is 0.95-1.05:1.
- Four wheel drive low is stuck OFF for 1.5 seconds with the TCC locked in 4th gear, and the transfer case ratio is 2.65-2.75:1.

ACTION TAKEN WHEN THE DTC SETS

^ The PCM freezes shift adapts from being updated.
^ The PCM assumes a non 4WD low state for stuck off transmission shift pattern.
^ The PCM assumes a 4WD low state for a stuck on transmission shift pattern.
^ The PCM illuminates the Malfunction Indicator Lamp (MIL).

CONDITIONS FOR CLEARING THE MIL/DTC
1. The PCM turns OFF the MIL after three consecutive ignition cycles without a failure reported.
2. A scan tool can clear the DTC from the PCM history. The PCM clears the DTC from the PCM history if the vehicle completes 40 warm-up cycles without a failure reported.
3. The PCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the PCM.

DIAGNOSTIC AIDS

^ Inspect the wiring for poor electrical connections at the PCM. Inspect the wiring for poor electrical connections at the transmission 20-way connector. Look for the following conditions:

- A bent terminal
- A backed out terminal
- A damaged terminal
- Poor terminal tension
- A chafed wire
- A broken wire inside the insulation

^ When diagnosing for an intermittent short or open condition, massage the wiring harness while watching the test equipment for a change.

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic chart.

3. Step 3 tests for a short to ground in circuit 1694.
4. Step 4 tests for an open in circuit 1694 or a faulty transfer case switch.