P085C
Gear Shift Control Module B Communication Circuit High
Transmission / module communication
Generic OBD-II
Medium
What it means
P085C means a high-voltage fault on the communication circuit to gear shift control module "B", so the transmission controller can't reliably talk to the shift module. The engine starts and runs, but the transmission may drop into a fail-safe mode with limited gear selection until the wiring or module is repaired. Corroded or wet connectors are a common trigger.
Medium
Can I keep driving? The engine runs, but the transmission may lose communication with the shift module and enter limp mode, limiting gear selection — get it diagnosed soon.
Common symptoms
What you'll notice
- Check-engine light on
- Transmission stuck in a fail-safe gear or won't shift normally
- Erratic or delayed gear changes
- Warning message about the transmission/shifter
Common causes
Most likely first
- Open or short-to-power on the shift-module communication wiringLikely
- Loose, corroded, or moisture-contaminated shift-module connectorCommon
- Faulty gear shift control module (B)Common
- Incompatible or incorrectly programmed replacement moduleLess often
How to diagnose & fix
Work through it in order
- Read freeze-frame and check for other communication (U-series) codes.
- Inspect the shift control module connector for corrosion or moisture and the wiring for opens/shorts.
- Verify supply voltage and ground to the module.
- Repair the communication circuit, then reflash or replace the shift module if it still won't communicate. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P085C?+
Only short-term. Losing shift-module communication can force limp mode with limited gears — have it checked before longer drives.
Can I just clear P085C?+
It returns until the wiring or module is repaired. Clearing does not restore the communication link.
Related codes
Often seen with P085C
Read & clear P085C 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