P1861

What it means

P1861 is a manufacturer-specific code that, in the definition given, means the transmission or transfer case control unit has seen the circuit for transfer case contact plate 'D' shorted to ground. The control unit expects a switched signal that changes with the transfer case position or range, and it found that circuit stuck at ground voltage. Which wire or switch segment is 'D' depends on the make, model and transfer case, so check the vehicle wiring diagram.

Symptoms

• Four-wheel-drive or transfer case warning light on the dashboard
• Transfer case will not shift between ranges or modes
• Drive mode or range indicator flashing, wrong or not displayed
• Transmission defaulting to fixed shift behaviour or limp mode on some models
• Engine management light on with the code stored

Possible causes

• Wiring to the transfer case chafed or pinched, shorting the signal wire to groundlikely
• Faulty transfer case contact plate or position switch with an internal short to groundlikely
• Water, dirt or corrosion in the transfer case connector bridging the signal to groundpossible
• Underbody damage or a poorly repaired harness near the transfer case or exhaustpossible
• Fault in the transmission or transfer case control unit input circuitrare
• Shift motor or selector mechanism out of position, giving an implausible switch patternrare

How to diagnose

1. Read all stored and pending codes and note the freeze frame data, including whether the fault is current or intermittent
2. Check live data for transfer case position or range and see whether the contact plate states match the selected mode
3. Inspect the harness from the control unit to the transfer case for chafing, heat damage, corrosion and signs of previous repairs
4. Disconnect and inspect the transfer case connector for water, corrosion and bent or pushed-back pins
5. With the ignition off and the connector unplugged, test the signal wire for continuity to ground using the wiring diagram
6. Test the contact plate resistance or switch states across the range of positions against the manufacturer's specification for that model
7. Check the supply and reference voltages at the connector, then wiggle the harness while monitoring live data for dropouts
8. Clear the code and road test, rechecking for return of the fault

How to fix

• Repair or replace the damaged section of wiring and secure it clear of sharp edges and heat sources
• Replace the transfer case contact plate or position switch if it tests faulty
• Clean, dry and repair the connector or terminals, and replace the connector if corroded or damaged
• Replace the harness if it is damaged internally or beyond a local repair
• Replace or repair the control unit only after the wiring and switch have been proven good, with any coding done to the manufacturer's procedure

Can I keep driving?

This code for other makes

• P1861VolkswagenThrottle Position Sensor Error Message From ECM

Nearby codes

• P1860OtherTCC PWM Solenoid Circuit Electrical/ Transmission Transfer Case Contact Plate 'D' Short Circuit To Battery
• P1862OtherTransmission Transfer Case Contact Plate Power Circuit Failure