P0860
Gear Shift Control Module A Communication Circuit
Transmission / module communication
Generic OBD-II
Medium
What it means
P0860 means the transmission control module has lost reliable communication with gear shift control module A over their shared circuit. Without that data link the system can't coordinate shifts, so the transmission may respond poorly or hold a single gear. The engine still starts and runs — this is a module-communication fault within the transmission system.
Medium
Can I keep driving? The engine starts, but shifting may be unreliable or stuck in one gear — have it checked before long trips.
Common symptoms
What you'll notice
- Check-engine light on
- Reduced or no response when shifting gears
- Transmission stuck in one gear (limp mode)
- Harsh or erratic shift patterns
Common causes
Most likely first
- Damaged or broken wiring in the communication circuitLikely
- Loose or corroded electrical connectors between the modulesCommon
- Failed gear shift control moduleCommon
- Failed transmission control module (rare)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and scan for other module or communication codes that point to the fault.
- Inspect the wiring and connectors between the gear shift control module and the transmission control module for damage or corrosion.
- Check the communication circuit for continuity and proper voltage, and repair any breaks or shorts.
- Replace the gear shift control module if it fails to communicate with wiring confirmed good. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P0860?+
The engine runs, but a communication loss can drop the transmission into limp mode, so limit driving until it's diagnosed.
Can I just clear P0860?+
It will clear briefly, but returns as soon as communication is lost again until the wiring or module is repaired.
Related codes
Often seen with P0860
Read & clear P0860 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX