P1875: How to Diagnose & Fix — 4WD Low Switch Circuit (GM)
2 vehicles · 2 makes · $200-$3,000 repair
How to diagnose and fix P1875: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
GMC Sierra 1500 · 2014–2015
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)
Kia Borrego · 2009–2011
The Borrego 4WD models use a BorgWarner transfer case that develops chain noise (whining/grinding) and can fail to engage 4WD or 4WD Lock modes. The transfer case chain stretches over time, and the encoder motor that controls mode selection can fail from water intrusion at the electrical connector. The transfer case fluid also breaks down faster than the 60,000-mile factory interval suggests, especially with towing or off-road use.
Common Symptoms
- Whining noise from underneath vehicle that increases with speed
- 4WD or 4WD Lock mode won't engage
- Service 4WD warning message
- Grinding noise when shifting between 2WD and 4WD
- Vibration at highway speed from driveline
How to Fix
Change transfer case fluid every 30,000 miles with the correct ATF specification. If chain noise is present, a transfer case rebuild or replacement is needed. The encoder motor can be replaced separately if 4WD mode selection is failing. Inspect the encoder motor wiring connector for corrosion — clean and apply dielectric grease to prevent future water intrusion. A used transfer case from a Mohave (the Borrego's international market name) can be sourced from import recyclers.
Owner tips & cautions
- TipChange transfer case fluid every 30,000 miles, not the factory 60,000 — the Borrego transfer case runs hotter than most due to vehicle weight
- TipInspect the encoder motor wiring connector for corrosion before replacing the motor itself — clean contacts and dielectric grease often fix engagement issues for free
- WarningDo not drive with 4WD engaged on dry pavement — this overloads the transfer case chain and accelerates wear
Sources for this issue (3)
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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?
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.
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?
Repair costs for P1875 range from $200 to $3,000, depending on the vehicle and root cause.
Which vehicles are affected by P1875?
Au7o has documented P1875 across 2 vehicle models from 2 manufacturers: GMC, Kia.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.