Technical Description of OBD-II Trouble Code
The circuit that senses generator voltage is registering a high reading.
What does that mean?
This is a generic diagnostic trouble code (DTC) that applies to many OBD-II vehicles (1996-newer), including vehicles from Jeep, Chrysler, Dodge, Ram, Cummins, Land Rover, Mazda, etc. Although it is a generic code, the exact repair steps may vary depending on the year, make, model, and powertrain configuration of the vehicle.
The P063D OBDII trouble code is associated with the circuit that senses generator voltage. When the Powertrain Control Module (PCM) detects improper signals within this circuit, it will set the P063D code. Depending on the vehicle and the specific malfunction, the battery warning light, check engine light, or both may illuminate. Other related codes associated with this circuit are P063A, P063B, P063C, and P063D.
The purpose of the generator voltage sense circuit is to monitor the voltage of the alternator and battery during vehicle operation. The alternator’s output voltage must be at a level that can compensate for battery draws from electrical components such as the starter, lighting, and various accessories. Additionally, the voltage regulator must adjust the output to provide sufficient voltage to charge the battery.
Code P063D is set by the PCM when it detects a high electrical condition in the generator (alternator) sense circuit.
Example of an alternator (generator):
What is the severity of this DTC?
The severity of this code can vary greatly. It can range from just an illuminated check engine light or battery warning light on a vehicle that starts and runs, to an automobile that will not start at all.
What are some of the symptoms of the code?
Symptoms of a P063D trouble code may include:
What are some of the common causes of the code?
Causes for this P063D code may include:
What are some P063D troubleshooting steps?
The first step in the troubleshooting process for any malfunction is to research the Technical Service Bulletins (TSB’s) for the specific vehicle by year, model, and power plant. This can save a lot of time in the long run by providing guidance in the right direction.
The second step is to conduct a thorough visual inspection to check the associated wiring for obvious defects such as scraping, rubbing, bare wires, or burn spots. Next, check the connectors and connections for security, corrosion, and damaged pins. This process should include all wiring connectors and connections to the battery, alternator, PCM, and voltage regulator. Some charging system configurations may be more complex, including relays, fuse-able links, and fuses in some cases. The visual inspection should also assess the condition of the serpentine belt and the belt tensioner. The belt should be tight with a slight amount of flexibility, and the tensioner must move freely and apply the appropriate amount of pressure on the serpentine belt. Depending on the vehicle and charging system configuration, a defective or damaged voltage regulator may require an alternator replacement in most cases.
Advanced Steps
The advanced steps are highly vehicle-specific and require the appropriate advanced equipment for accurate performance. These procedures necessitate a digital multimeter and the specific technical references for the vehicle. Ideally, a charging system diagnostic device should be used if available. Voltage requirements will vary based on the specific year and model of the vehicle.
Voltage Checks
The battery voltage should be approximately 12 volts, and the alternator output must be higher to compensate for electrical draws and charge the battery. The absence of voltage indicates a faulty alternator, voltage regulator, or a wiring issue. If the alternator voltage output falls within the appropriate range, it suggests that the battery requires replacement or a wiring issue exists.
If this process identifies the absence of a power source or ground, continuity testing may be required to check the integrity of the wiring, alternator, voltage regulator, and other components. Continuity tests should always be performed with the power removed from the circuit, and the normal readings for wiring and connections should be 0 ohms of resistance unless otherwise specified by the technical data. Resistance or no continuity indicates faulty wiring that is open or shorted and must be repaired or replaced.
What are some common repairs for this code?
Common mistakes may include:
We always recommend seeking professional service to address this issue. However, if that is not possible, we offer the option to permanently delete this specific DTC while keeping all other codes intact. If you are interested in this option, please upload your ECU file to our portal.
