U0133: Lost Communication With Active Roll Control Module
What to do
The car will lean more in corners than you are used to, and feel less settled at speed. It is safe to drive; just allow for it.
Your car has anti-roll bars it can stiffen and soften rather than fixed ones, and this code means the computer controlling them has stopped talking to the rest of the car. The system has defaulted to a fixed setting, so the car now handles like an ordinary one.
The reason this page exists is that the change gets blamed on the wrong thing. "The car has gone soft in corners" is normally investigated as worn shock absorbers, tired bushes or sagging springs — and those parts get replaced without fixing anything, because the suspension is fine. If this code is stored, say so before agreeing to any suspension work.
If your vehicle is one that disconnects its bars for off-road use, stop relying on that — it will lift a wheel earlier on uneven ground than you expect.
The usual causes are the wiring and connectors at the axles, which live in the road salt and flex with the suspension, or on hydraulic systems the pump's power supply.
What this code means
The active roll control module has stopped being heard from. The general reasoning is at U0100, and U0434 covers the same module reporting implausibly instead.
Active roll control replaces a fixed anti-roll bar with one the vehicle can stiffen, soften or disconnect — hydraulically on older systems, with 48-volt electric actuators on newer ones. It exists because the two things an anti-roll bar has to do are in conflict: stiff enough to keep a tall vehicle flat through a corner is too stiff to let a wheel drop into a rut, and a controllable bar can be both.
When the module goes quiet the system defaults to a fixed state, and the vehicle reverts to behaving like one with ordinary anti-roll bars.
The consequence is a handling change rather than a failure, and it is worth naming because of how it gets diagnosed. The vehicle leans noticeably more in corners than its driver is used to, and feels less settled on a motorway. That is normally investigated as worn dampers, tired anti-roll bar bushes or dropped springs — parts that get replaced without changing anything, because the suspension is fine and the system that was flattening it has switched off.
So a stored roll control code alongside a "the car has gone soft" complaint is the cheap explanation, and it should be eliminated before anything is unbolted.
On the off-road side the loss runs the other way. A vehicle that decouples its bars for articulation cannot do so, so it lifts wheels earlier on uneven ground. That is a capability to stop relying on rather than a hazard.
Where the fault is: actuators and their wiring live at the axles, in the spray and salt, on harnesses that move with the suspension through their whole travel. Hydraulic systems add a pump and a pressure sensor whose supply is a common single point of failure.
Likely causes
Start here
- Corroded or loose connector · easy
- Damaged wiring harness · moderate
- Water ingress into the module connector · moderate
- Blown fuse or failed supply · easy
Less common
- Failed power or earth supply to the module · moderate
- Damaged data bus wiring · 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
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
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.
- What actually fixed it — or that nothing did, which is worth knowing too.
Sign in or create an account to add what you found about U0133.