Feedback switch signal wire chafed or shorted to ground in the harness; Faulty differential lock feedback switch (internal short); Water ingress or corrosion in the switch connector or transfer case wiring; Damaged or contaminated switch from oil leaks or debris at the transfer case; Mechanical or actuator fault in the lock-up mechanism causing an abnormal switch state, depending on model; Fault inside the controlling module affecting the feedback input.

P1845

Transmission Transfer Case Differential Lock-Up Feedback Switch Short Circuit To Ground.

Other
Powertrain
Manufacturer code
Medium severity

How this code is built

P: SystemPowertrain
1: Defined byThe manufacturer
8: AreaTransmission
45: FaultThe specific fault in that area

What it means

P1845 is a manufacturer-specific code. For the vehicles that use the definition 'Transfer Case Differential Lock-Up Feedback Switch Short Circuit To Ground', the control unit sees the lock-up feedback signal pulled to ground when it should not be. The unit cannot confirm the real position of the differential lock, so it sets the fault. Some makes, including several General Motors brands, use P1845 for a different fault (gear ratio output circuit), so confirm the definition for your specific vehicle before diagnosing.

Symptoms

Differential lock or four-wheel drive warning light on the dashboard
Differential lock will not engage or disengage when selected
Transfer case or diff lock indicator flashing or showing the wrong state
Drive mode selection limited or refused
Transmission or four-wheel drive fault message
Odd driveline binding in tight turns if the lock is stuck engaged

Possible causes

Feedback switch signal wire chafed or shorted to ground in the harnesslikely
Faulty differential lock feedback switch (internal short)likely
Water ingress or corrosion in the switch connector or transfer case wiringlikely
Damaged or contaminated switch from oil leaks or debris at the transfer casepossible
Mechanical or actuator fault in the lock-up mechanism causing an abnormal switch state, depending on modelpossible
Fault inside the controlling module affecting the feedback inputrare

How to diagnose

Confirm the code definition for this exact make, model and year using manufacturer data, as P1845 means different things on different vehicles
Read all stored codes and freeze frame data, noting whether the fault is current or intermittent, then clear and see if it returns
Check the live data for the differential lock feedback switch state while selecting and deselecting the lock
Visually inspect the wiring and connector at the transfer case switch for chafing, rubbing, corrosion, moisture and oil contamination
With the connector unplugged and ignition off, test the signal wire for continuity to ground and check it against the wiring diagram
Test the switch itself against the manufacturer's resistance or continuity specification in each position
Check the transfer case for leaks, damage and correct operation of the lock mechanism
Check the module's supply and earth connections before suspecting the module itself

How to fix

Repair or replace the damaged wiring section and secure it away from sharp edges or heat
Clean, dry and repair the connector, replacing terminals or seals if corroded
Replace the faulty feedback switch and seal it correctly
Repair any transfer case leak and replace contaminated components
Repair or replace the lock actuator or mechanism if it is found to be at fault
Replace or reprogram the control module only after wiring and switch faults are ruled out and manufacturer data supports it

Can I keep driving?

Medium severity

The car can usually be driven carefully on the road for a short time, but have it checked soon. Avoid off-road or low-grip use, and avoid tight turns on hard surfaces if the lock may be stuck engaged, as this can stress the driveline.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.