Circuit Description
WARNING: This page is about a different car, the 2003 GMC Sonoma, 2003 GMC Jimmy, 2003 Chevrolet S10 Pickup, and 2003 Chevrolet Blazer. However, it is still accessible from the selected car via links, so may be relevant.
The four wheel drive (4WD) low circuit consists of the powertrain control module (PCM), a transfer case control module (TCCM) and the circuit wiring. The TCCM controls the 4WD low signal on the signal circuit. When the operator selects 4WD low, the TCCM grounds the signal circuit and the 4WD low signal voltage on the circuit changes from ignition voltage to zero volts. The PCM then compensates for transfer case gear reduction in the transmission output shaft speed (OSS) signal. The PCM uses the transmission OSS signal 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 B DTC.