P0631Generic code

P0631 Code: VIN Not Programmed or Mismatch - TCM

The P0631 code means the transmission computer does not have the VIN stored, or the number does not match. It is normally solved by programming or configuring the module with the right equipment.

Severity
Medium
Can I keep driving?
Yes, but with caution
Estimated cost
$0 to $1,500
Difficulty
Hard
System
Computer and Outputs
Applies to
All OBD2 vehicles

Updated Reviewed by Renzo Chacca

On this page

What the P0631 code means

This works the same way as P0630, but in the transmission computer. The P0631 code shows up when a new transmission computer, or one from another vehicle, is installed without being programmed.

Before you condemn the computer, always check its power supply and grounds. Low voltage, a loose battery terminal or a corroded ground can cause internal errors that disappear as soon as the connection is fixed. It is also worth looking for manufacturer software updates, because many of these codes are cleared by reflashing the computer without replacing it.

If the computer does have to be replaced, keep in mind that it almost always needs to be programmed: VIN, immobilizer, option configuration and, on many vehicles, relearn procedures afterward. A used computer that has not been programmed can leave the vehicle unable to start.

P0631 code symptoms

  • Check engine light on.
  • The engine may not start or may run in limp mode.
  • Other codes stored at the same time in several systems.

Likely causes of the P0631 code

  1. Computer not programmed or set up wrong after a replacement.
  2. Programming interrupted by a loss of voltage during the process.
  3. Wrong computer from another vehicle or another version.

How to diagnose the P0631 code step by step

  1. Clear the code and see whether it comes back. Some are caused by a one-time event, such as a discharged battery.
  2. Measure the voltage at the computer power pins and compare it with the battery voltage.
  3. Measure the voltage drop across the grounds. It should be under 0.1 volts under load.
  4. Look for technical service bulletins and software updates for your vehicle.
  5. Inspect the computer connector for moisture, corrosion or bent pins.

How to fix the P0631 code

  • Correct the power supply and ground problems.
  • Reprogram or update the computer.
  • Set up or program the VIN, options and keys if needed.
  • Clear the codes and verify the repair.

Technical reference data

  • Supply voltage: battery voltage, with less than 0.2 volts of drop.
  • Programming needs stable voltage, so connect a battery maintainer first.
  • Reference values: check the manufacturer data for your vehicle.

Brand-specific notes

Manufacturers publish software updates that fix many of these internal computer codes. Ask the dealer before you buy a replacement computer.

P0631 on Ford

Ford has released updates for similar internal computer codes such as P0606. Ask the dealer whether one applies to your vehicle.

P0631 on Chrysler

Chrysler has also published updates for similar internal computer codes such as P0606. Check with the dealer before replacing the module.

P0631 on Hyundai

Hyundai is another brand that has released updates for similar internal computer codes such as P0606. Check with the dealer before replacing the module.

Frequently asked questions about P0631

What does the P0631 code mean?
It is a generic OBD2 code that means the transmission computer has no VIN stored, or the VIN does not match the vehicle. It usually appears after a computer was replaced.
Can I drive with a P0631 code?
With caution. It depends on the symptoms: if the vehicle shifts normally you can drive carefully to a shop, but if it goes into limp mode, have it taken to a mechanic.
Does the computer have to be replaced?
Not always. Many times the cause is the power supply, a ground or the software, and programming the module solves it.
Can I use a used computer?
Only if it is programmed correctly for your vehicle. An unprogrammed used unit can leave the vehicle unable to start.
How much does it cost to fix P0631?
It can cost $0 if the cause was just the battery or a loose ground. If the computer has to be replaced and programmed, the cost can reach $1,500.
What is the most common cause of P0631?
For a P0631 code, the usual culprit is a transmission computer that was replaced and never programmed for the vehicle. An interrupted programming session caused by low voltage is the next most common reason.

Related codes

Questions about the P0631 code

There are no questions about this code yet. Tell us about your case: vehicle, symptoms and what you have already checked.