Error Code P0631 is defined as VIN Not Programmed or Incompatible – TCM. This code is a generic trouble code, which means it applies to all vehicles equipped with OBD-II system, especially those made since 1996 up to present. It’s particularly common among Chrysler, Dodge, Ford, Hyundai, and Toyota models. Specifications on the definition, troubleshooting, and repairs, of course, vary from one make and model to another.
When Error Code P0631 is stored, that means the TCM (transmission control module) doesn’t recognize the 17-character VIN (Vehicle Identification Number).
Each vehicle produced in North America is assigned with a VIN, which is a combination of numbers and letters that denote the manufacturer’s country, year, make, and model, including special equipment and energized size/type. The last 6 digit at the end of the VIN provides the sequence where each vehicle is produced. A VIN is unique, and no two vehicles are assigned to a specific number.
Since the inception of the OBD-II diagnostic system, VIN has been programmed into the PCM (after being installed to the vehicle). Other controllers can also be programmed to recognize the VIN, but the federal mandate says that PCM is programmed as such.
The primary reason for the VIN is to discourage vehicle theft and prevent tampering with the odometer. This is because system controllers can’t be swapped from one vehicle to another without the program to match the vehicle. Vehicle mileage is also programmed to the PCM. If a controller is swapped between vehicles, digits in the odometer would be far less accurate and unreliable. When PCM is replaced, it must be programmed with the odometer reading and its corresponding VIN (among other things). The TCM is programmed the same way for the same reason.
If the PCM is unable to recognize the VIN, then it will trigger the Check Engine light and register the Error Code P0631. The PTM searches for the VIN as soon as the key is turned on and the self-test run. In most cases, TCM will not function without the VIN recognition.
- Engine shutdown (especially when rolling to a stop)
- Erratic or harsh transmission shift patterns
- Vehicle security may be activated
Other error codes may be present as well.
- TCM programming error
- TCM swapped between vehicles or replaced without proper reprogramming
- Failed TCM
How to Check
Unlike most error codes, P0361 is related to TCM failure or programming error in the TCM. Due to the delicate nature of certain parameters that must be programmed to the PCM (mileage, VIN), reprogramming equipment access is limited only to qualified personnel. Thus, without the tool to reprogram the troubled controller, successful repair for this problem is highly unlikely.
For proper diagnosis of this code, you will need a diagnostic scanner and a reliable source of vehicle information. Use the vehicle information source for the applicable TSB (Technical Service Bulletin). Find a TSB that matches with the vehicle make and model, symptoms of the problem, and code stored, as this will help you to point to the right direction.
Check all connectors and wirings. Repair or replace damaged, disconnected, corroded, shorted connectors, components, and wirings as necessary.
Retest the system after doing any repair. If all wirings and components (including fuses) are in good condition, then connect the scanner to the vehicle diagnostic port and read the VIN as shown in the PCM. Record all stored codes and their freeze frame data. This information can be helpful in diagnosing an intermittent condition.
Clear the code and then try to operate the vehicle to see if the code returns. This will determine whether the malfunction is intermittent or not. If the code proves to be intermittent after a test drive, then you may have to wait it out and allow the problem to get worse before you can successfully diagnose the condition.
If the problem is NOT intermittent, then compare VIN on the diagnostic scanner to the actual VIN (found in the lower driver side of the windshield). If the VIN displayed on your scanner does NOT match the etched VIN tag, then suspect that the PCM has been swapped from another vehicle.
If the VIN is not shown in the scanner, then you can suspect a replaced PCM without programming it to match the vehicle. If this is not the case, then you can suspect a programming error or failed PCM.
In many cases, aftermarket replacement PCM (programmed to match the vehicle) may be purchased. If this is possible, then you will need to provide the parts vendor with the mileage and VIN of the vehicle, including other pertinent data required.
Unfortunately, though, there is no foolproof method for testing PCM. Nevertheless, it’s usually safe to assume that barring any controller replacement without proper programming, some type of controller failure took place.
How to Fix
- Reprogramming of TCM and PCM
- All connectors and wirings related to the TCM must be checked, repaired, or replaced as necessary
Note that any OBD-II controller replacement will require reprogramming.