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DTC codes / P0Axx · Hybrid propulsion / P0AB8

P0AB8Engine Mount B Control Circuit High

P0AB8 indicates that the powertrain control module (PCM) has detected an abnormally high voltage on the control circuit for engine mount B, which is typically an active or electronic engine mount used to reduce vibration. The PCM commands the mount to change stiffness or damping, and a high voltage reading on the control circuit usually points to an open circuit, a short to voltage, or a failed mount actuator.

SystemPowertrain
Code typeGeneric (all makes)
SeverityLow
Fix difficultyIntermediate
AreaHybrid propulsion

Symptoms you may notice

  • Illumination of the check engine light, often with no other noticeable symptoms.
  • Increased vibration or harshness felt through the steering wheel, seat, or floorboards, especially at idle or during certain engine speeds.
  • A noticeable clunk or thud from the engine bay when accelerating or decelerating, if the mount fails to adjust properly.
  • Rough idle quality or excessive engine movement that may be felt as a shudder.
  • In some cases, the vehicle may enter a reduced-performance mode or set related codes for other systems.

Common causes, most likely first

  1. Open circuit in the control wire between the PCM and the engine mount actuator, such as a broken wire or disconnected connector.
  2. Short to voltage on the control circuit, often caused by chafed wiring contacting a power source.
  3. Failed engine mount actuator (solenoid or electronic valve) that has an open internal coil or is stuck in one position.
  4. Corroded or damaged electrical connector at the engine mount or PCM, leading to high resistance or intermittent connection.
  5. PCM internal fault, though this is less common and should only be considered after other causes are ruled out.
  6. Aftermarket or improper electrical modifications that interfere with the mount control circuit.

How to diagnose and fix it

  1. Inspect the engine mount actuator connector and wiring for visible damage, corrosion, or loose pins, and repair as needed.
  2. Disconnect the mount actuator and measure the resistance of the actuator coil; compare to the manufacturer's specification to check for an open or shorted coil.
  3. With the actuator disconnected and the key on, measure voltage on the control circuit at the PCM side to verify whether the high voltage is present due to a short to power or a PCM issue.
  4. Perform a wiggle test on the wiring harness while monitoring the circuit with a multimeter or scan tool to detect intermittent opens or shorts.
  5. If the circuit tests good, command the mount actuator with a scan tool to verify operation and listen for clicking or observe movement if applicable.
  6. Replace the engine mount actuator if it fails electrical or functional testing, and clear the code to verify the repair.
  7. If all else fails, check for technical service bulletins (TSBs) or software updates for the PCM that may address false setting of this code.

What a high voltage mount code really means

  • A high voltage code on an actuator control circuit often indicates an open circuit rather than a short, because the PCM pulls the circuit high when it detects no current flow through the actuator.
  • Many electronic engine mounts are vacuum-operated or electrically controlled, and a failed vacuum supply or a cracked mount can cause similar symptoms without setting this specific code, so always verify the mount's mechanical condition.
  • The engine mount control circuit may share a ground or power with other sensors or actuators, so a fault elsewhere in the shared circuit can trigger this code as a secondary effect.
  • On some vehicles, the engine mount is only active during certain driving conditions, such as idle or low-speed driving, so a fault may not be noticeable during a test drive.
  • A scan tool that can read live data for the mount command and actual position (if available) is invaluable for confirming whether the PCM is commanding the mount and whether the mount is responding.

Can I keep driving with P0AB8?

The vehicle is generally safe to drive with this code because the engine mount is a comfort feature and does not affect engine operation or safety directly. However, prolonged driving with a failed mount can lead to increased vibration and potential wear on other components, so have it inspected at your earliest convenience.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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