DTC P1875: 4-WHEEL DRIVE LOW SWITCH CIRCUIT Chevrolet Silverado 2500

Note. For circuit identification, see CONNECTOR IDENTIFICATION and WIRING DIAGRAMS .

Circuit Description

DTC P1875 detects abnormal conditions of the 4-wheel drive indication switch input, and 4-wheel drive status using speed and gear ratios. DTC P1875 is a type "X" DTC.

Conditions For Running The DTC

DTC will run under the following conditions

1. The components are powered, and ignition voltage is greater than 9 volts and less than 18 volts.
2. Engine speed is greater than 200 RPM and less than 7500 RPM for 5 seconds.
3. Output speed sensor circuit DTCs P0721 and P0722 are not active.
4. Output speed is above 60 RPM.
5. Transmission fluid temperature is between 68°F (20°C) and 266°F (130°C).
6. Shift is complete and Neutral is not selected.

Conditions For Setting The DTC

DTC will set under one of the following conditions

1. The transfer case switch indicates high range, and the calculated range is low range for 5 seconds or more.
2. The transfer case switch indicates low range, and the calculated range is high range for 5 seconds or more.

Action Taken When The DTC Sets

TCM performs the following actions if DTC is set

1. DTC will be stored in the TCM history.
2. TCM inhibits TCC engagement.

Conditions For Clearing The DTC

DTC will clear under the following conditions

1. A scan tool can clear the DTC from the TCM history.
2. The TCM automatically clears the DTC from the TCM history if the vehicle completes 40 warm-up cycles without failure.

Test Description

The numbers listed below refer to step numbers in the diagnostic procedure

1. 2 This step tests the status of the 4WD low switch.
2. 3 This step tests for a 4WD switch failure to ground.
3. 4 This step tests for a short in the wiring harness.
4. 9 This step tests for a 4WD switch failure to an open state.
5. 10 This step tests for an open in the wiring harness.