U0300

Internal Control Module Software Incompatibility

Car Fault Codes Network

Can you still drive? With care, short trips only

Who can fix it? Needs a specialist or dealer

Typical repair time 1 hour – 4 hours

Typical cost SAR 200 to 3,000

What it means

A control module has detected that its software or configuration (coding) does not match the vehicle or the other modules on the network. It usually appears after a module is replaced or reprogrammed, for example when a used module from another vehicle is installed or an update is interrupted before it finishes.

Symptoms4

Check engine or other warning lights on after a module replacement or programming.
Some functions work incorrectly or not at all, depending on the affected module.
Invalid data or lost communication codes in other modules.
In some cases a no-start because the immobilizer rejects the module.

Possible causes5

A module with a part number or software version that does not suit the vehicle.
Coding or setup not performed after installing a new or used module.
Update or programming interrupted before completion, often by low battery voltage.
One module updated without updating related modules that need a matching version.
Corrupted internal module software.

How to diagnose5

Read codes from all modules and identify which module stored the code.
Check the repair history: was a module replaced or reprogrammed recently?
Compare the module part number and software version with what the manufacturer specifies for the VIN.
Check the battery and make sure voltage is stable before any programming.
Look for manufacturer service bulletins or known updates for this code.

How to fix5

Complete the required coding or setup for the module with a suitable scan tool.
Reprogram the module with the correct version, with a stable battery charger connected during programming.
Update related modules if the manufacturer requires matching versions.
Replace an unsuitable module with the correct part number, then program it.
Clear codes in all modules and confirm the code does not return.

Repair cost

0–500

500–2,000

2,000–5,000

5,000+

In Saudi riyals; the highlighted part is the expected range for this fault.

The cost is usually limited to programming or coding fees, and rises if the installed module is the wrong one and must be replaced and programmed again.

Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.
Prices last updated: September 2026

Frequently asked questions

Why did the code appear after replacing a computer?

A new or used module usually needs programming and coding for your vehicle. If that was not done, or the version is different, the module detects the mismatch.

Is clearing the code enough?

No. The code will return because the mismatch is still there. The real fix is correct programming or coding with the right version.

This guide is for information only and does not replace an inspection by a qualified technician. If the fault involves brakes, steering, engine temperature, electrics or refrigerant, do not attempt the repair yourself.

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