Fault code P0A5B – generator current sensor circuit low

Fault code P0A5B is called “Generator Current Sensor Circuit Low” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.

Technical description and explained code P0A5B

The P0A5B fault code is intended to be displayed only on hybrid vehicles. Indicates that the powertrain control module (PCM) has detected a low signal level in the alternator voltage sensor circuit.

Fault code P0A5B – generator current sensor circuit low

The cause of this malfunction may be the resolver, which is a sensor. It is used to determine the magnetic pole positions of the rotor, which is necessary to ensure precise control of the electric motor (MG2).

Each resolver contains a stator that has an excitation coil and 2 detection coils (S, C). As the rotor rotates, the gap between stator and rotor changes because the rotor is oval shaped. A current with a given frequency flows through the excitation winding and the output AC current of the detection windings S and C changes according to the rotor position of the sensor.

The MG ECU installed in the inverter-inverter assembly determines the absolute rotor position based on the phases and amplitudes of the S and C field winding signals. In addition, the processor calculates the change in position over a certain time interval, resulting in the resolver being used as a speed sensor.

The MG ECU monitors the output signal of the alternator resolver. If the MG ECU detects that the output signals do not match the reference characteristics, it registers an alternator resolver fault.

The hybrid system’s PCM then turns on the MIL indicator lamp and displays fault code P0A5B.

Symptoms of vehicle malfunctions

The main signal that an error P0A5B has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.

It can also be warning signs such as:

  1. The “Check engine” control lamp on the control panel will light up (the code will be stored as a fault).
  2. Other related fault codes may also be present.
  3. The internal combustion engine cannot be started.

The severity of fault P0A5B is high, you should eliminate the cause as soon as possible. Because its occurrence can lead to more serious consequences.

Factors that can cause this error code

The error code P0A5B can mean that one or more of the following problems have occurred:

  • Problem with the resolver of the generator.
  • Inverter inverter assembly.
  • Electric motor of hybrid system.
  • Hybrid system alternator.
  • Rear traction motor with transmission assembly.
  • Wiring harness or connectors (inverter, generator, electric motor, rear electric motor).

How to fix or reset OBD-2 code P0A5B

Some suggested steps for troubleshooting and fix the error code P0A5B:

  1. Read all stored data and error codes with an OBD-II scan tool.
  2. Clear the error codes from the computer memory.
  3. Test-drive the vehicle to find out if error P0A5B appears again.
  4. Visually inspect the wires and connectors going to the inverter, generator, electric motor, rear electric motor.
  5. Check the inverter-inverter assembly, hybrid system motor, hybrid system generator, and rear traction motor with drivetrain assembly.

Diagnose and repair of problems

The first step in the P0A5B troubleshooting process is to review the maintenance bulletins (TSB). In some cases, this can save you a lot of time in the long run by pointing you in the right direction.

A common cause of this error is moisture entering damaged or poorly snapped connectors. So you need to check the inverter, generator and motor resolver connector on the box, as well as the connector on the rear electric motor.

It is also worth checking all the wiring harnesses related to the electrical equipment described above. It is worth paying attention to scuffs, meltings and other damage, and if necessary, repair or replace the wires.

After repairing the defective connector or damaged wiring, the P0A5B error is likely to be eliminated. If not, there may be an inter-phase short in the circuit caused by water ingress.

Therefore, it is better to entrust the next steps of troubleshooting to professionals, as they involve testing of expensive equipment. If defects are detected, they must be eliminated or replaced by a specialist.

If an inter-phase short circuit has occurred, the hybrid transmission assembly may have to be replaced to clear the P0A5B code.

On which vehicles does this problem occur most frequently

Fault code P0A5B can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:

  • Ford
  • Jeep

Fault code P0A5B can sometimes be found with other errors. The most common are the following: P0A59, P0A5A, P0A5C.


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