P0860 moderate

Gear Shift Module Communication Circuit

The P0860 code means the vehicle's onboard diagnostic system has detected: Gear Shift Module Communication Circuit. This is a moderate severity code.

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Keep driving?: Short distances only
DIY difficulty: hard
Estimated cost: $200 - $1,000 (parts and labor)

Check Your Fluid First

ANCEL AD310 OBD-II Scanner

Read and clear transmission codes. Many trans codes are caused by low or burnt fluid -- check level and color before assuming the worst.

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Read Transmission Codes

LAUNCH CRP123X (Reads All Systems)

Basic scanners only read engine codes. This reads transmission, ABS, and airbag too.

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Common Symptoms

Check Engine Light illuminated
Transmission does not respond to shift lever inputs
Vehicle may be stuck in Park or current gear
Multiple transmission-related warning lights

Probable Causes (Ranked by Likelihood)

Gear shift module communication failure Very High
CAN bus wiring fault between shift module and TCM High
Faulty gear shift module Moderate
TCM CAN bus input failure Low

Step-by-Step Diagnostic Procedure

Scan for CAN bus communication DTCs in all modules
Check CAN bus wiring between the shift module and TCM for opens or shorts
Verify CAN bus termination resistors are within specification
Test gear shift module power and ground circuits

Frequently Asked Questions

What is a gear shift module?

In vehicles with electronic shifters (shift-by-wire), a gear shift module converts the driver's gear selection into an electronic signal sent to the TCM over the CAN bus network.

Can P0860 leave me stuck in Park?

Yes, if the TCM cannot communicate with the gear shift module, it may not receive the command to exit Park. Some vehicles have a manual park release for emergencies.

Is this common with electronic shifters?

Electronic shift-by-wire systems can develop communication issues over time, especially with connector corrosion or CAN bus wiring problems. They are more complex than traditional cable-operated shifters.