What Does P0C08 Mean?
This code indicates an open circuit condition or general circuit fault in the Drive Motor B three-phase power circuit (Phase U, V, and W collectively). The motor controller has detected that one or more phases of Motor B cannot conduct current, preventing the motor from generating torque. In a dual-motor vehicle, this completely disables the secondary drive unit, significantly impacting vehicle performance and AWD capability.
Safety Warning
An open phase circuit completely disables Motor B. In AWD configurations, loss of Motor B eliminates rear (or front) axle drive and regenerative braking, drastically altering vehicle dynamics, especially in adverse conditions. The vehicle should be towed for service by a qualified EV technician.
Common Causes
30%
Loose or corroded high-voltage phase conductor connection at Motor B or its inverter
25%
Motor B stator winding open circuit in one or more phases
20%
Motor B inverter power stage open-circuit failure (IGBT/MOSFET)
15%
High-voltage phase cable damage or disconnection in the Motor B circuit
10%
High-voltage interlock loop (HVIL) fault on the Motor B circuit disconnecting power
Diagnostic Steps
1
Review freeze-frame data to determine if the open circuit was detected during a startup diagnostic check or during active motor operation.
2
With the high-voltage system properly de-energized and locked out, visually inspect all Motor B phase connections at both the motor terminal box and the inverter output terminals.
3
Measure continuity through each of the three phase conductors from the inverter output to the Motor B terminals to identify the open circuit location.
4
Measure Motor B phase winding resistances at the motor terminal box — an open reading on any phase indicates an internal motor winding failure.
5
If cables and motor windings show continuity, test the Motor B inverter power stage for open-circuit IGBT/MOSFET failures.
6
Check all HVIL connectors in the Motor B high-voltage circuit for proper engagement and continuity.
Estimated Repair Cost
$500 - $5,000
Parts + labor, varies by vehicle and location
This code indicates an open circuit condition or general circuit fault in the Drive Motor B three-phase power circuit (Phase U, V, and W collectively). The motor controller has detected that one or more phases of Motor B cannot conduct current, preventing the motor from generating torque. In a dual-...
The most common cause of P0C08 (Drive Motor "B" Phase U-V-W Circuit/Open) is: Loose or corroded high-voltage phase conductor connection at Motor B or its inverter
Typical repair costs for P0C08 range from $500 to $5,000, depending on the vehicle, location, and whether you do it yourself or go to a shop.
An open phase circuit completely disables Motor B. In AWD configurations, loss of Motor B eliminates rear (or front) axle drive and regenerative braking, drastically altering vehicle dynamics, especially in adverse conditions. The vehicle should be towed for service by a qualified EV technician.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0C08 to identify the root cause.
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Quick Info
Category
Powertrain
System
Hybrid/EV Drive Motor System
Difficulty
Type
Generic (SAE)
Recommended Tools
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