What it means
The active engine mount B control circuit reports a control circuit low condition. Vibration damping cannot be modulated.
At a glance
- Usually lights the check-engine light
How it works
Active engine mount B has an actuator that lets the control module adjust vibration damping. P0AB7 sets when the module detects the mount B control signal below its expected range, commonly from a wire shorted to ground, an internally shorted actuator, or resistance at a corroded connector.
Common causes
Most likely first.
- Control wire shorted to ground
- Actuator internal short
- Connector pins corroded - high contact resistance
Symptoms
- Check-engine light may illuminate
- Increased engine vibration, especially at idle
- Clunk or thump when starting, stopping, or shifting
How to diagnose it
- Use a scan tool to record freeze-frame data and see whether the code returns at idle or during changes in engine load.
- Inspect mount B's connector and harness for corrosion, damaged insulation, or a wire contacting ground.
- Check connector pins for corrosion or poor contact that could add resistance to the mount B circuit.
- With the wiring diagram, test the mount B signal circuit for a short to ground and compare readings with the manufacturer's specification.
- If the harness and connector pass, test the mount B actuator and module output using the specified procedure.
Common fixes
- Clean and secure corroded mount B connector terminals if they can be serviced.
- Repair a mount B control wire shorted to ground.
- Replace damaged connector terminals or the connector.
- Replace the mount B actuator if it has an internal short.
Can I keep driving?
A gentle trip to a repair location may be possible if vibration and clunking are mild; avoid hard acceleration and abrupt shifts. Severe engine movement or worsening impacts can damage nearby components.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.