Technical Description of OBD-II Trouble Code
Performance Issue with Internal Control Module Vehicle Speed
What does that signify?
This is a generic diagnostic trouble code (DTC) that pertains to OBD-II vehicles. This includes various vehicles such as , etc. Although it is a generic code, the specific repair steps may differ depending on the year, make, model, and powertrain configuration.
When the code P062C is stored, it indicates that the powertrain control module (PCM) has detected an internal performance error with the vehicle speed sensor (VSS) signal. Other controllers may also detect an internal PCM performance error related to the VSS signal, resulting in the storage of code P062C.
The internal control module monitoring processors are responsible for performing various self-tests on the controllers and ensuring overall accountability of the internal control module. The PCM and other related controllers constantly monitor the VSS signal input and output. The transmission control module (TCM), traction control module (TCSM), and other controllers interact with the VSS signal.
The VSS is typically an electromagnetic sensor that interacts with a toothed reluctor ring, wheel, or gear that is mechanically attached to an axle, transmission/transfer case output shaft, or driveshaft. As the axle rotates, the reluctor ring also rotates. The notches in the reluctor ring create interruptions in the electromagnetic sensor circuit as they pass by the sensor in close proximity. The PCM (and other controllers) receive these interruptions as waveform patterns. The faster the waveform patterns are input into the controller, the higher the estimated vehicle speed. As the input of waveform patterns slows down, the controller perceives a decrease in vehicle speed. These input signals are compared between modules via the controller area network (CAN).
Whenever the ignition is on and the PCM is powered, self-tests are initiated for the VSS signal. In addition to running internal controller self-tests, the controller area network (CAN) also compares signals from each individual module to ensure proper functioning of each controller. These tests are performed simultaneously.
If the PCM detects discrepancies in VSS inputs/outputs, it stores the code P062C and may illuminate the malfunction indicator lamp (MIL). Additionally, if the PCM detects a discrepancy between any of the on-board controllers, indicating an internal VSS error, it stores the code P062C and may illuminate the MIL. Depending on the perceived severity of the malfunction, multiple failure cycles may be required for MIL illumination.
Photo of a PCM with the cover removed:
What is the severity of this DTC?
Codes related to internal control module processors should be considered severe. A stored code P062C can result in erratic automatic transmission shift patterns and erratic speedometer/odometer operation.
What are some of the symptoms of the code?
Symptoms of a P062C trouble code may include:
What are some of the common causes of the code?
Causes for this P062C DTC code may include:
What are some P062C troubleshooting steps?
Diagnosing a code P062C can be challenging even for experienced technicians. Reprogramming may also be necessary for controller replacement, which requires the appropriate equipment.
If there are ECM/PCM power supply codes present, they should be addressed before diagnosing a P062C. VSS codes, if present, should also be diagnosed and repaired first.
Prior to declaring an individual controller defective, several preliminary tests can be performed. These tests require a diagnostic scanner, a digital volt/ohmmeter (DVOM), and reliable vehicle information. An oscilloscope can also be helpful for testing the VSS and VSS circuits.
Connect the scanner to the vehicle diagnostic port and retrieve all stored codes and freeze frame data. Record this information in case the code is intermittent. After recording the information, clear the codes and test drive the vehicle until the code is reset or the PCM enters readiness mode. If the PCM enters readiness mode, the code is intermittent and more difficult to diagnose. In some cases, the condition that caused the P062C to be stored may need to worsen before a diagnosis can be made. If the code is reset, continue with the following preliminary tests.
When diagnosing a P062C, information is crucial. Search for technical service bulletins (TSB) that match the stored code, vehicle (year, make, model, and engine), and symptoms. A relevant TSB may provide diagnostic information that can greatly assist in the diagnosis.
Use the vehicle information source to obtain connector face views, connector pin-out charts, component locators, wiring diagrams, and diagnostic flow charts related to the code and vehicle in question.
The VSS output can be tested with either the scanner (data stream) or the oscilloscope while the drivetrain is engaged. Narrowing the data stream to display only pertinent fields increases the accuracy of the displayed data when using the scanner. Look for inconsistent or erratic readings from the VSS.
The oscilloscope provides a more accurate data sample. Use the positive test lead to test the VSS signal circuit, with the negative test lead grounded to the battery. Watch for glitches or voltage spikes in the VSS signal circuit waveform pattern.
If necessary, the DVOM can be used to perform a resistance test on the VSS sensor (and VSS circuits). Replace sensors that do not comply with the manufacturer’s specifications.
Use the DVOM to test controller power supply fuses and relays. Test and replace blown fuses as required. Fuses should be tested with the circuit loaded.
If all fuses and relays appear to be functioning properly, visually inspect the controller-related wiring and harnesses. Also check the chassis and engine ground junctions. Use the vehicle information source to obtain ground locations for related circuits. Use the DVOM to test ground integrity.
Visually inspect system controllers for signs of water, heat, or collision damage. Any damaged controller, especially due to water, should be considered defective.
If the controller power and ground circuits are intact, suspect a defective controller or a controller programming error. Controller replacement will require reprogramming. Aftermarket sources may offer reprogrammed controllers for some vehicles. Other vehicles/controllers may require on-board reprogramming that can only be done through a dealership or qualified source.
