P1875 on GMC: How to Diagnose & Fix
4WD Low Switch Circuit (GM)
1 GMC model · 1 documented issue · 1 critical
P1875 on GMC by model: symptoms, diagnosis and fix
An electrical signal short in the transfer case can cause it to shift to neutral without driver input while driving. This results in sudden loss of power to the wheels creating a serious safety hazard, particularly at highway speeds or when towing.
Common Symptoms
- Sudden loss of power while driving
- Transfer case shifts to neutral unexpectedly
- Service 4WD message on dash
- Vehicle rolls freely as if in neutral
How to Fix
Recall repair: Replace transfer case encoder motor and reprogram transfer case control module. Inspect and repair wiring harness.
Sources for this issue (1)
P1875 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P1875 mean on a GMC?
P1875 stands for "4WD Low Switch Circuit (GM)." P1875 is a GM-specific code indicating a fault in the 4WD low switch circuit, which is monitored by the transmission/transfer case or vehicle control module. This switch tells the control module when four-wheel-drive low range is selected so the system can adjust transmission and transfer-case behavior. The code sets when the module sees a continuous open, short to ground, or short to power in that circuit. You may have trouble engaging or disengaging 4WD low and may see a 4WD or service warning light. On GMC it is documented across 1 model: Sierra 1500.
What are the most common causes of P1875?
The most common causes of P1875 are: Faulty 4WD low range switch, Open or shorted wiring in the 4WD low switch circuit, Corroded or loose connector at the switch or transfer case, Damaged wiring harness near the transfer case, Faulty transfer case control / encoder motor, Poor ground or chafed wire, Failed transfer case or transmission control module (less common). The specific cause varies by vehicle.
How much does it cost to fix P1875 on a GMC?
Repair costs vary widely with the root cause and GMC model; each issue on this page carries its own estimate where one is published.
Looking for P1875 on a different make?
View P1875 across all makes →Join 600+ people using Au7o to better understand their vehicles.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.