Technical Description of OBD-II Trouble Code
The range/performance of the Generator Voltage Sense Circuit
What does that signify?
This is a generic diagnostic trouble code (DTC) that is applicable to many OBD-II vehicles (1996-newer). This includes 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.
The P063B OBDII trouble code is associated with the generator voltage sense circuit. When the Powertrain Control Module (PCM) detects improper signals within the generator voltage sense circuit, code P063B will be set. Depending on the vehicle and the specific malfunction, the battery warning light, check engine light, or both will be illuminated. Related codes associated with this circuit are P063A, P063B, P063C, and P063D.
The purpose of the generator voltage sense circuit is to monitor the alternator and battery voltage during vehicle operation. The output voltage of the alternator must be at a level that can compensate for battery draws from electrical components such as the starter, lighting, and various other accessories. Additionally, the voltage regulator must adjust the output to provide sufficient voltage to charge the battery.
Code P063B is set by the PCM when it detects an out-of-range situation or performance problem within 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, ranging 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 P063B trouble code may include:
What are some of the common causes of the code?
Causes for this P063B code may include:
What are some P063B 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. In some circumstances, this can save a lot of time in the long run by pointing you in the right direction.
The second step is 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 must include all wiring connectors and connections to the battery, alternator, PCM, and the voltage regulator. Some charging system configurations may be more complex, including relays, fuse-able links, and fuses in some circumstances. The visual inspection should also include 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. Based on the vehicle and the charging system configuration, a defective or damaged voltage regulator will require an alternator replacement in most circumstances.
Advanced Steps
The advanced steps become very vehicle specific and require the appropriate advanced equipment to perform accurately. These procedures require a digital multimeter and the specific technical references for the vehicle. The ideal tool to use in this situation is a charging system diagnostic device, 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 as well. The lack of voltage indicates a faulty alternator, voltage regulator, or a wiring issue. If the alternator voltage output is within the appropriate range, this is an indication 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 is an indication of 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:
Hopefully, the information in this article has been helpful in pointing you in the right direction to correct the problem with your generator voltage sense circuit fault code. This article is strictly informational, and the specific technical data and service bulletins for your vehicle should always take priority.
