U0552 Low Generic / SAE

U0552: Invalid Data Received From Running Board Control Module B

Network and Communication Invalid Data Received (continued)

What to do

The car drives normally. The powered step may not come out, may be slow, or may come out only sometimes.

Treat it as not working, and tell your passengers. These are tall vehicles, and a step that appears unreliably is more dangerous than one that never appears — somebody steps down expecting it to be there.

The usual cause is corrosion and grit, not electronics. The mechanism lives under the sill in the path of everything the front wheel throws up. Washing that area out and mentioning any grinding or slowness will help — a step that has been getting stiff for months is telling the same story as this code.

If the vehicle is used on salted roads or off-road, say so. It changes how quickly this comes back after a repair, and whether the mechanism is worth protecting.

What this code means

Running board control module B is broadcasting data that cannot be accepted as true. See U0400 for what an invalid-data code is and why the module it names is usually the messenger rather than the culprit.

Before anything is diagnosed, establish that the vehicle actually has this equipment.

This is optional kit, and the commonest cause of a code naming it is a car that was told it has one when it does not. A body control module or gateway coded to a higher specification, a second-hand module carrying its donor vehicle's configuration, or a retrofit that was wired in but never coded — all three report equipment that is not there, and none of them is a fault in the vehicle.

Nothing is broken in that case and nothing needs replacing. The repair is a coding correction, and it is quick when somebody asks the question first.

A powered running board is the step that swings out when a door opens on a large SUV or pickup, and it is mounted in the worst place on the vehicle for electronics.

It lives under the sill, below the door, ahead of the rear wheel — in the direct path of everything the front tyre throws up. Salt, grit, mud and standing water reach it constantly, and the mechanism is expected to move through all of it.

So corrosion is not a failure mode here, it is the default one. A seized or stiff mechanism makes the motor draw current the module cannot reconcile with the travel it measures, and the module rejects the data. A step that has become slow, noisy or partial is describing the same fault this code names.

The safety consequence is worth stating plainly, because these vehicles are tall. A step that deploys unreliably is worse than one that does not deploy at all, since a passenger stepping down expects it to be there. Assume it will not appear until it is repaired.

Where the letter is B, the vehicle has steps on both sides — and a fault on only one is useful information, because everything the two share is proven good.

Likely causes

Start here

Module not coded to the vehicle · specialist
Second hand module locked to another vehicle · specialist
Corroded or loose connector · easy
Corroded earth connection · moderate
Water ingress into connector · moderate

Less common

Damaged data bus wiring · moderate
Incorrect module configuration after replacement · specialist
Physical damage from road debris · moderate

Symptoms

Components involved

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.

Community experience

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The car — make, model, year and engine. The same fault behaves differently on each.
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