U0442 High Generic / SAE

U0442: Invalid Data Received From Engine Control Module B

Network and Communication Invalid Data Received Emissions related

What to do

Expect reduced power, possibly a rough-running engine, and several warnings at once.

Some engines are managed by two computers rather than one — a large V engine may run one per bank, and some diesels split the work between two units. They constantly check each other's figures, and this code means they have stopped agreeing.

That is worth knowing because neither computer has to be faulty for it to happen. A single sensor that both of them read, giving a slightly different answer to each, is enough.

Do not let either module be replaced on the strength of this code alone. They are among the most expensive parts on the car and normally have to be programmed to the vehicle. Ask for the other stored codes to be read and dealt with first — a fault naming a specific sensor is almost certainly the real problem.

What this code means

A second engine control module is broadcasting data that cannot be accepted as true. See U0400 for the family's framing and U0401 for the first module.

The useful question is which vehicles have a second engine module at all, because the answer changes what this code means.

Large V-configuration engines sometimes run a module per bank, each managing its own cylinders while the pair agree about the engine as a whole.
Some heavy diesels split engine control from fuel-injection control across two units.
Several manufacturers designate a supervisory module as B — the unit that arbitrates between engine, transmission and, on a hybrid, the electric drive.

On a vehicle with only one engine module, this is a configuration problem rather than a fault — software expecting a partner that does not exist, which is what happens when a calibration for a different variant is loaded or a second-hand unit is fitted.

Where two modules genuinely exist, the important point is that they check each other. Each publishes values the other can verify, and the code sets on disagreement — which means neither module need be faulty for it to appear. A sensor read by both, or a figure each computes from a shared input, is enough: one arrives at a slightly different number, the pair stop agreeing, and the check fails.

So the sequence is the family's usual one: read the other stored codes first. A specific sensor fault alongside this is very likely why the two modules stopped agreeing, and replacing either module is an expensive way to discover that.

Likely causes

Start here

Faulty receiving module input · specialist
Corroded or loose connector · easy
Damaged data bus wiring · moderate
Software updated on one module only · specialist

Less common

Module not coded to the vehicle · specialist
Faulty engine control module · specialist

Symptoms

Components involved

Information, not instruction

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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.

Community experience

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