Error Code P062C is defined as Internal Control Module Vehicle Speed Performance. This is a generic trouble code, meaning it applies to all vehicles equipped with the OBD-II system. Specifications on the definition, troubleshooting, and repairs, of course, vary from one make and model to another.
When Error Code P062C is stored, that means the PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes) has determined an internal performance error in the VSS (vehicle speed sensor) signal. Other controllers can also detect an internal PCM performance error (in fuel injection control system) and cause this code to be stored.
The Internal Control Module monitoring processors are responsible for different controller self-test duties and overall internal control module accountability. Both input and output signals of the VSS are subject to self-test and are constantly being monitored by the PCM and other related controllers. The TCM (transmission control module), TCSM (traction control module), and other controllers are subject to the interaction of the fuel injection control system.
The VSS is an electromagnetic sensor that interacts with some type of toothed reluctor, gear, or wheel, which is affixed mechanically to an axle, driveshaft, or transmission/transfer case output shaft. The reluctor ring spins as the axle spins. As the reluctor passes closely through the sensor, the notches in the reluctor ring make interruptions in the electromagnetic sensor circuit. These interruptions are seen by the PCM (and other controllers) as waveform patterns. The faster patterns being input to the controller, the higher the estimated vehicle speed. When the input of the wave pattern slows down, the vehicle speed estimation (as perceived by the controller) also decreases. These input signals are compared (between modules) through the CAN (controller area network)
Every time the ignition is turned On, and the PCM is energized, the self-test for VSS will initiate. Simultaneously, CAN (controller area network) will also compare signals from each module to ensure each controller is working properly.
If the PCM sees discrepancies in inputs/outputs of VSS, then it Error Code P062C will appear, and simultaneously trigger the Check Engine light. Additionally, if the PCM sees a discrepancy between any of onboard controller, which would indicate internal VSS error, P062C will be stored as well.
In some cases, depending on the perceived severity of the problem, multiple failure cycles may be needed for the Check Engine light to activate.
- Erratic odometer or speedometer operation
- Irregular shift patterns in transmission
- Activation of Check Engine lamp, Traction Control lamp, or Antilock Brake lamp
- ABS and Traction Control codes may be stored
- Unexpected activation of antilock braking to the traction control system (if equipped)
- ABS system stored, making the vehicle inoperable
- Defective controller programming
- Defective VSS
- Excessive debris buildup on VSS
- Damaged or worn teeth on the reluctor ring
- Blown fuse
- Bad controller power relay
- Open or shorted circuit or connectors in CAN harness
- Open or shorted circuit between PCM and VSS
- Insufficient control module ground
How to Check
This code is quite a challenging problem to diagnose, and many times, it involves reprogramming issues. Thus, without the right tools and reprogramming equipment, it will be impossible to replace a defective controller and complete the repair.
If the PCM power supply codes are present, then obviously, they don’t need to be rectified before attempting to diagnose this code.
There are many preliminary tests that can be performed prior to make sure a controller is defective. A diagnostic scanner, DVOM (digital volt/ohmmeter), and reliable vehicle information is needed for diagnosis of this code. An oscilloscope can also be helpful when testing the VSS and VSS circuits.
The first step is to connect the scanner to the vehicle diagnostic port and retrieve all stored codes, including their freeze frame data. You need to write down this information, just in case the problem proves to be intermittent. After writing down all pertinent information, clear the codes and then take the vehicle for a test drive to see if the code resets, or if the PCM enters readiness mode. If the PCM does the latter, then you have an intermittent problem, which is more difficult to diagnose, as it means you would have to wait for the problem to develop more before you can successfully diagnose.
If the code resets, however, then continue with your preliminary diagnosis.
When trying to diagnose this code, refer to your information source or TSB (technical service bulletin); looks for signs and symptoms parallel to the stored code. Search for the year, make, model, and engine of your vehicle. If you are able to find the right TSB, then you may get the best diagnostic information for your problem.
Use vehicle information source to obtain component locations, connector face views, connector pin-out charts, wiring diagram, and diagnostic flow chart related to your vehicle’s error code.
To test the VSS output, you can use either the scanner (data stream) or the oscilloscope, with the drivetrain engaged. If you opt to use the scanner, narrow the data (so it will show only pertinent fields) to increase accuracy. Watch out for inconsistent or erratic readings from the VSS.
The oscilloscope provides more accurate data sample. Use positive test lead to test the VSS signal circuit (negative test lead grounded to the battery). Watch for glitches or voltage spikes in the VSS signal circuit waveform pattern.
The DVOM may be used to perform a resistance test on the VSS sensor (and VSS circuits) if necessary. Replace sensors that do not comply with the manufacturer’s specifications.
If all fuses and relays are running well, check whether the controller related wiring and harness are in order. You may also want to check chassis and engine ground junctions. Again, use your vehicle information source to obtain ground locations as related circuits. Test ground integrity using the DVOM.
Then, check the system controllers for any signs of water, heat, or collision damage. Any controller that is damaged, especially by water, is considered defective and must be replaced.
If controller power and ground circuits are intact, then there’s a good chance the controller is defective, or there’s a programming error in the controller. Thus, controller replacement requires reprogramming. In some cases, you may want to get aftermarket reprogrammed controllers. Some vehicles and controllers require on-board reprogramming that may be done only through the dealership or a qualified shop.
How to Fix
Depending on your diagnosis, possible repairs include:
- Replacement of blown fuses
- Replacement and reprogramming of defective controller
Unlike most codes, this code is likely caused by a defective controller or a programming error in the controller.
Test the integrity of the system ground by connecting the negative test lead of DVOM to the ground, and the positive test leads to battery voltage.