Damaged, chafed or corroded wiring or connector on the engine mount B control circuit (short to earth or high resistance); Faulty engine mount B solenoid or actuator with an internal short or low resistance; Water ingress or contamination in the mount connector causing a low signal; Wiring damaged where it moves with the engine, for example near the mount, brackets or harness clips; Fault in the control unit output driver for the mount; Outdated control unit software where the manufacturer has issued a correction for this fault.

P0AB7

Engine Mount B Control Circuit Low.

Generic
Powertrain
Generic code
Low severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
A: AreaHybrid propulsion
B7: FaultThe specific fault in that area

What it means

P0AB7 means the control unit has detected a low voltage or signal on the control circuit for engine mount B, an electronically controlled (active or switchable) mount. The unit commands the mount and sees a circuit voltage lower than expected, which points to a short to earth, an open circuit or a fault in the actuator or driver. Which mount is 'B' and how it is controlled depends on the model and engine, so check the manufacturer wiring information.

Symptoms

Engine warning light on, possibly with a stored fault only
Increased vibration or shake at idle, especially in gear with the engine warm
Noticeable engine judder or shuffle when starting, stopping or changing load
More noise or harshness through the body at certain engine speeds
Mount stuck in one damping mode, giving a firmer or rougher feel than usual

Possible causes

Damaged, chafed or corroded wiring or connector on the engine mount B control circuit (short to earth or high resistance)likely
Faulty engine mount B solenoid or actuator with an internal short or low resistancelikely
Water ingress or contamination in the mount connector causing a low signalpossible
Wiring damaged where it moves with the engine, for example near the mount, brackets or harness clipspossible
Fault in the control unit output driver for the mountrare
Outdated control unit software where the manufacturer has issued a correction for this faultrare

How to diagnose

Read all stored codes and freeze frame data, noting engine speed, temperature and battery voltage when the fault set, and check for other circuit or voltage faults
Check battery condition and charging voltage, as low supply voltage can cause circuit faults
Visually inspect the wiring and connector at engine mount B for chafing, heat damage, corrosion, water and loose pins
Check the wiring route and clips near the mount for rubbing against the body, bracket or engine
With the connector unplugged, measure the mount actuator resistance and compare it with the manufacturer specification
Test the control wire for a short to earth and continuity back to the control unit, with the control unit disconnected
Use a bi-directional test to command the mount, then check for a change in the circuit voltage and the mount's response
Check for any manufacturer software updates or bulletins for this code on the specific model

How to fix

Repair or replace damaged wiring, and secure the harness away from rubbing or heat
Clean, dry and repair the connector, or replace it if the terminals are corroded or loose
Replace the engine mount B or its solenoid or actuator if its resistance or operation is out of specification
Replace the control unit only if the driver circuit is proven faulty after wiring and the actuator are cleared
Update the control unit software only if the manufacturer lists it as a fix for this fault

Can I keep driving?

Low severity

The car can normally be driven, but expect more vibration and noise from the engine. Book it in soon, as a worn or poorly controlled mount can put extra strain on other mounts and the drivetrain.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.