Fault code P0A8B – 14 volt power module system voltage malfunction

Fault code P0A8B is called “14 Volt Power Module System Voltage Malfunction” 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 P0A8B

This diagnostic trouble code (DTC) is a generic code. Error P0A8B is considered a general code because it applies to all makes and models of vehicles. Although the specific repair steps may vary slightly depending on the model.

Fault code P0A8B – 14 volt power module system voltage malfunction

This error code is defined as a “low voltage system fault”. It is set when the Powertrain Control Module (PCM) detects an abnormal 14 V power module voltage value.

The current in the low voltage system is closely monitored by the 14 V power module. Which is also known as the auxiliary DC power module. An error code will be stored in the system by the 14 volt power module and the low voltage system will be deactivated.

This problem is an electrical malfunction. And readings that are below or above the programmed range will cause the warning light on the instrument panel to go off. Also error code P0A8B will be stored and recorded as a fault.

Symptoms of vehicle malfunctions

The main signal that an error P0A8B has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.

It can also be warning signs such as:

  1. Check engine control lamp on the control panel will light up (the code will be recorded in the memory as a fault).
  2. The low voltage system is not working properly.

The P0A8B error is quite serious, as it may cause problems in the electrical system. It may also affect the functioning of other vehicle systems. Therefore, it is advisable to correct the error as soon as possible when the fault is detected.

Factors that can cause this error code

The error code P0A8B can mean that one or more of the following problems have occurred:

  • Damaged 14-volt power module.
  • Open or short circuit in 14-volt power module harness.
  • Weak electrical connection in 14-volt power module circuit.
  • Power Module software is executing erratically and needs to be updated.
  • Sometimes faulty PCM is the cause.

How to fix or reset OBD-2 code P0A8B

Some suggested steps for troubleshooting and fix the error code P0A8B:

  1. Make sure that the battery is fully charged and in working order.
  2. Inspect the wiring and wiring connectors for damage.
  3. Replace the 14-volt power module if defective.
  4. Update the 14-volt power module software.
  5. If the error persists, check the PCM module.

Diagnose and repair of problems

The first step in the P0A8B troubleshooting process is to review the Technical Service Bulletins (TSB). For known problems with your particular vehicle.

It is a good idea to start troubleshooting by visually inspecting the wires for possible damage or malfunctions. Any possible damage should be repaired immediately.

The 14-volt power module should then be carefully inspected for damage or defects. If a problem is found, it should be corrected immediately. Sometimes an error code is stored in the vehicle if the 14 volt power module software is not updated. Therefore, this should be checked and the software should be updated.

Checking the battery

Make sure the battery is fully charged, check for signs of acid buildup on the terminals. Also, check that the terminal connections are secure and clean, repair or replace the terminals if necessary.

Make sure all electrical consumers are turned off or disconnected and check the system to make sure the battery is not running low. If a leak is found, isolate all circuits one at a time to determine the culprit, and repair if necessary.

Check the battery under load and replace it if a defect is found. Clear all codes and retest the system to make sure the fault does not return. If the battery is operating according to the specifications in the manual. No fault is found in the wiring, proceed to the alternator test.

Testing the alternator

Make sure all wiring is connected, connect the OBD-2 scanner, and check the alternator output with the engine running. If the alternator output reading is 14 volts or less, the alternator may be faulty, but you need to check the wiring.

Check all primary and secondary ground connections to make sure all connections are good. Poor grounding often leads to overheating at the connection points. Therefore, check all cable lugs for signs of burning, scorching or sparking. Repair if necessary.

Note that the alternator output should be within 14.2V when the engine is running at idle. And about 14.6 V when the engine speed increases.

If the code holds and there is no fault in the wiring, but the charge rate is not as specified, the alternator is faulty. However, this must be confirmed with a scan tool. If a scanner is not available, a multimeter should be used to confirm the alternator malfunction.

Intermittent malfunction or PCM failure

The actions described above apply to most vehicles and should clear the P0A8B code. However, if the code returns, it is likely that an intermittent fault may be present. In this case, you will have to allow the problem to worsen before accurate diagnosis and final repair can be made.

There is also the possibility that abnormal system voltage could damage the PCM if the PCM is controlling the alternator output. If this is the case, the PCM should be replaced, reprogrammed, and the vehicle checked. To see if any codes come back.

On which vehicles does this problem occur most frequently

Fault code P0A8B can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:

  • Chevrolet
  • Ford
  • Hyundai
  • Mazda

Fault code P0A8B can sometimes be found with other errors. The most common are the following: P0A8C, P0A8D, P0A8E, P0A8F.


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