Cause
Software updated on one module only
Two modules that used to agree no longer do, because one of them was reprogrammed and the other was not.
Modules do not simply exchange numbers; they exchange numbers in a format both ends have to understand, and manufacturers change those formats between software versions — a value gains a bit of resolution, a message is split in two, a field means something slightly different. A module updated to a newer version speaks the newer dialect to a partner still expecting the old one, and the receiver rejects what it gets as impossible rather than misreading it.
That is why this shows up as invalid data rather than as lost communication. Everything is arriving, on time and correctly formed. Only the content is unacceptable.
The diagnostic signature is timing, and it is decisive: this appears immediately after work rather than out of nowhere. A dealer visit, a recall action, a module replaced, an over-the-air update, a retrofit. A fault that started the day the car came back from somewhere is this until shown otherwise, and the question worth asking is not what broke but what changed.
The fix is a software level, not a part. Bringing every module on the affected network to the manufacturer's current released set is the repair, and replacing hardware in the meantime achieves nothing — a new module arrives with whatever version the supplier shipped, which may be neither of the two already fitted.
One practical warning. Reprogramming needs stable voltage for the whole session, and a battery that sags part-way through leaves a module worse off than before — see the calibration integrity argument at U0441.
Typically specialist work. Needs equipment or training most home workshops do not have.
Some of these codes mean you should stop driving
1 of the 79 codes this can cause indicate a fault where continuing to drive risks damage or is unsafe. Which one you have matters more than the cause does — read the code's own page before deciding.
Codes this can cause (79)
Codes where this is a likely explanation first, rather than merely a possible one.
- U0301 Software Incompatibility With Engine Control Module Likely for this code High
- U0302 Software Incompatibility With Transmission Control Module Likely for this code High
- U0303 Software Incompatibility With Transfer Case Control Module Likely for this code Moderate
- U0304 Software Incompatibility With Gear Shift Control Module A Likely for this code High
- U0305 Software Incompatibility With Cruise Control Module Likely for this code Moderate
- U0306 Software Incompatibility With Fuel Injector Control Module Likely for this code High
- U0307 Software Incompatibility With Glow Plug Control Module 1 Likely for this code Moderate
- U0308 Software Incompatibility With Throttle Actuator Control Module Likely for this code High
- U0309 Software Incompatibility With Alternative Fuel Control Module Likely for this code Moderate
- U0310 Software Incompatibility With Fuel Pump Control Module Likely for this code Moderate
- U0311 Software Incompatibility With Drive Motor Control Module Likely for this code High
- U0312 Software Incompatibility With Battery Energy Control Module A Likely for this code High
- U0313 Software Incompatibility With Battery Energy Control Module B Likely for this code High
- U0314 Software Incompatibility With Four-Wheel Drive Clutch Control Module Likely for this code Moderate
- U0315 Software Incompatibility With Anti-Lock Brake System (ABS) Control Module Likely for this code High
- U0316 Software Incompatibility With Vehicle Dynamics Control Module Likely for this code High
- U0317 Software Incompatibility With Park Brake Control Module Likely for this code Moderate
- U0318 Software Incompatibility With Brake System Control Module A Likely for this code High
- U0319 Software Incompatibility With Steering Effort Control Module Likely for this code Moderate
- U0320 Software Incompatibility With Power Steering Control Module Likely for this code Moderate
- U0321 Software Incompatibility With Suspension Control Module A Likely for this code Moderate
- U0322 Software Incompatibility With Body Control Module Likely for this code Moderate
- U0323 Software Incompatibility With Instrument Panel Control Module Likely for this code High
- U0324 Software Incompatibility With HVAC Control Module Likely for this code Moderate
- U0325 Software Incompatibility With Auxiliary Heater Control Module Likely for this code Moderate
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
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