What does it mean?
This is a generic diagnostic trouble code (DTC) and applies to many OBD-II vehicles (1996-newer). This may include, but is not limited to, vehicles from Jeep, Chrysler, Dodge, Ram, Cummins, Land Rover, Mazda, etc. Although generic, the exact repair steps may vary depending on the year, make, model, and powertrain configuration.
The OBDII trouble code P063B is associated with the generator voltage sensing circuit. When the Powertrain Control Module (PCM) detects incorrect signals in the generator voltage sensing circuit, the P063B code is set. Depending on the vehicle and the specific malfunction, the battery warning light, the check engine light, or both will be illuminated. Related trouble codes associated with this circuit are P063A, P063B, P063C, and P063D.
The purpose of the generator voltage sensing circuit is to monitor the alternator and battery voltage during vehicle operation. The alternator’s output voltage must be at a level capable of compensating for the electrical load from components, including the starter, lighting, and various other accessories. Additionally, the voltage regulator must adjust the output to provide sufficient voltage to charge the battery.
The P063B code is set by the PCM when it detects an out-of-range condition or a performance issue in the generator (alternator) sensing circuit.
Example of an alternator (generator):
P063B Alternator
How severe is this DTC?
The severity of this code can vary greatly, from a simple check engine light or battery warning light on a vehicle that starts and runs, to an automobile that does not start at all.
What are some of the symptoms of the code?
Symptoms of a P063B trouble code may include:
Battery warning light illuminated
Engine does not start
Engine cranks slower than normal
Check engine light illuminated
What are some common causes of the code?
Causes
of this P063B code may include:
Faulty alternator
Faulty voltage regulator
Loose or damaged serpentine belt
Faulty serpentine belt tensioner
Blown fuse or fusible link (if applicable)
Corroded or damaged connector
Corroded or damaged battery cable
Faulty or damaged wiring
Faulty PCM
Faulty battery
What are the troubleshooting steps for P063B?
The first step in the troubleshooting process for any malfunction is to search for Technical Service Bulletins (TSBs) for the specific vehicle by year, model, and powertrain. In some circumstances, this can save a lot of time in the long run by pointing you in the right direction.
The second step involves a thorough visual inspection to check that the associated wiring does not have obvious defects such as chafing, rubbing, exposed wires, or burn marks. 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, fusible links, and fuses in certain circumstances. The visual inspection should also include the condition of the serpentine belt and belt tensioner. The belt should be tight with some deflection visible, and the tensioner should move freely and apply the appropriate amount of pressure to the serpentine belt. Depending on the vehicle and the charging system configuration, a faulty or damaged voltage regulator will require alternator replacement in most circumstances.
Advanced Steps
Advanced steps become very vehicle-specific and require appropriate advanced equipment to perform accurately. These procedures require a digital multimeter and vehicle-specific technical references. The ideal tool to use in this situation is a charging system diagnostic device, if available. Voltage requirements will be highly dependent on the specific year and model of the vehicle.
Voltage Checks
The battery voltage should be properly at 12 volts, and the alternator output should be higher to compensate for electrical loads and to charge the battery as well. A lack of voltage indicates a faulty alternator, voltage regulator, or a wiring issue. If the alternator’s voltage output is within the appropriate range, this indicates that the battery needs to be replaced or that a wiring problem exists.
If this process identifies a missing power source or ground, continuity tests 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 disconnected from the circuit, and normal readings for wiring and connections should be 0 ohms of resistance, unless otherwise specified by the technical data. Resistance or a lack of continuity is an indication of faulty wiring that is open or shorted and must be repaired or replaced.
What are the common repairs for this code?
Alternator replacement
Replacement of a blown fuse or fusible link