Fault code P065C is called “Generator Mechanical Performance” 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 P065C
OBD-II fault code P065C is a generic fault code defined as “alternator mechanical performance”. It is set when the Powertrain Control Module (PCM) detects low performance of the alternator system.
The alternator is designed to generate the current needed by the vehicle at a given time. This is accomplished by a circuit in the control module that evaluates the total power consumption.
If any alternator control circuit fails or malfunctions, some modules may not have enough power to function. The fuel and ignition control modules, though, may operate until the battery runs out of power.
Therefore, if poor system performance is detected when checking the alternator control circuit, code P065C will be stored and the malfunction indicator lamp (MIL) may illuminate. Depending on the perceived severity of the fault, it may take several failure cycles for the MIL to illuminate.
Symptoms of vehicle malfunctions
The main signal that an error P065C has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.
It can also be warning signs such as:
- The “Check engine” control lamp on the control panel will light up (the code will be stored as a fault).
- Other related fault codes may also be present.
- The vehicle system voltage may be either abnormally high or abnormally low.
- Some gauges or gauges on the dashboard may be inactive.
- The engine stalls or starts poorly.
- Decreased engine power.
A stored fault code P065C can cause various driving problems, including no starting or a low battery. Therefore, internal control module errors should always be taken seriously.
Factors that can cause this error code
The error code P065C can mean that one or more of the following problems have occurred:
- Faulty alternator.
- Faulty alternator control module.
- Open or short circuit in wiring harness.
- Loose or damaged connectors.
- Poor grounding is a common cause.
- Low charge level or full discharge of the battery pack.
- Voltage surges caused by improper starting procedures from an external source.
- Sometimes the cause is a faulty PCM module or programming error.
How to fix or reset OBD-2 code P065C
Some suggested steps for troubleshooting and fix the error code P065C:
- Read all stored data and error codes with an OBD-II scan tool. To find out when and under what circumstances error P065C appeared.
- Clear the error codes from the computer memory and test-drive the vehicle to find out if the malfunction appears again.
- If the error code appears again, visually inspect the electrical wiring and control module connector.
- Visually inspect and test the alternator.
- If necessary, repair or replace the alternator and any defective wires.
- Check the voltage regulator and battery pack.
- If there are no defects, check the PCM module itself and its software part.
Diagnose and repair of problems
Fault code P065C is rarely found without other codes. Associated codes usually refer to abnormal system voltages (high or low). And also to performance range mismatch codes, which may refer to different sensors.
If there are no additional codes, the first thing to do is to check the battery to determine its state of charge and overall performance. If the battery is discharged or damaged, recharge or replace it.
Checking the wiring
After checking the battery, visually inspect all wiring associated with the alternator. If necessary, repair or replace to ensure effective load transfer.
If no visible signs of shorts or other damage are found, use a voltmeter to check the resistance and ground. Replace if necessary to ensure that all electrical values are within the limits specified by the manufacturer.
Also locate any fuses that are in any way connected to the charging system. After checking, replace any damaged or suspect fuses.
Testing the alternator
If all the wiring is checked, you need to test the alternator itself with a multimeter. In most cases, a faulty alternator is the cause of error P065C.
If the defect in the alternator is confirmed, replace it with a new or rebuilt alternator, as this is almost always more cost-effective than a repair. However, make sure that the unit being replaced is identical to the original in all respects, including mounting brackets and specifications.
After replacement, start the engine and watch the indicator light on the dashboard to make sure the alternator is working properly. The warning light should go out within a few seconds.
You can also measure the system voltage, it should be between 14.2 and 14.8 volts. Allow the vehicle to run at least one full drive cycle before rescanning the system. Most likely there will be no P065C error, but sometimes additional clearing with the scan tool is necessary.
On which vehicles does this problem occur most frequently
Fault code P065C can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:
- Chrysler
- Dodge
- Ford (Fiesta, Focus, Mondeo)
- GMC
- Land Rover (Range Rover)
- Mazda
- Nissan
Fault code P065C can sometimes be found with other errors. The most common are the following: P065A, P065B.
