What Does P085C Mean?
The gear shift control module "B" communication circuit is reading a high voltage condition. This elevated voltage typically indicates a short to battery power in the wiring, an open ground in the circuit, or the module has failed in a way that drives the communication line high. Communication with the shift control module is compromised.
Common Causes
30%
Short to battery voltage in the communication circuit
25%
Open ground circuit for the gear shift control module "B"
25%
Faulty gear shift control module "B"
12%
Disconnected or corroded connector causing open circuit
8%
TCM communication line driver failure
Diagnostic Steps
1
Measure the communication circuit voltage at the module connector and at the TCM connector — verify the high-voltage condition exists.
2
Disconnect the gear shift control module "B" — if voltage drops, the module is driving the line high. If voltage remains high, the wiring has a short to power.
3
Verify the ground circuit for the module has proper continuity to chassis ground — an open ground can cause the communication line to float high.
4
Check for wiring damage near the shifter mechanism, center console, or underdash area where the communication harness routes.
5
If the module is confirmed faulty, replace and reprogram per manufacturer procedures.
Estimated Repair Cost
$200 - $900
Parts + labor, varies by vehicle and location
The gear shift control module "B" communication circuit is reading a high voltage condition. This elevated voltage typically indicates a short to battery power in the wiring, an open ground in the circuit, or the module has failed in a way that drives the communication line high. Communication with ...
The most common cause of P085C (Gear Shift Control Module "B" Communication Circuit High) is: Short to battery voltage in the communication circuit
Typical repair costs for P085C range from $200 to $900, depending on the vehicle, location, and whether you do it yourself or go to a shop.
The electronic shift system may be disabled or in a fail-safe mode. The vehicle may be unable to shift or stuck in a single gear. If the vehicle cannot shift safely, have it towed to a repair facility.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P085C to identify the root cause.
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Quick Info
Category
Powertrain
System
Transmission / Electronic Shift Control
Difficulty
Type
Generic (SAE)
Recommended Tools
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