U0135: Lost Communication With Differential Control Module — Front
What to do
Two minutes in a car park will tell you which version of this you have, and it changes how much it matters.
Your car has a front differential it can lock or bias electronically for traction, and this code means the computer controlling it has stopped talking to the rest of the car.
Usually it simply releases, and the car drives entirely normally on the road while losing traction on mud, snow or a slippery slope. Nothing is at risk; just do not rely on it in bad conditions.
The test: drive slowly in a full-lock circle on dry tarmac. If the car binds, judders or skips its front tyres on tight lock, and is fine when you straighten up, the differential has stayed locked. That one is worth taking seriously — it loads the driveline and scrubs the tyres — so drive as little as possible until it is fixed.
Mention that test result to the garage. Binding on full lock is routinely investigated as a CV joint, a gearbox fault or a sticking brake, and it is none of those. Saying "it only does it on full lock and there is a differential code stored" saves a great deal of money.
What this code means
The front differential control module has stopped being heard from. The general reasoning is at U0100, and U0436 covers the same module reporting implausibly instead.
A controllable front differential is either a locker — clutches or a dog clutch that tie the two front wheels together for traction — or a torque-vectoring unit that biases drive toward the outer wheel in a corner. Both are electronically commanded, and both revert to something when the command stops.
Which way they revert is the whole diagnosis, and a driver can establish it in a car park in two minutes.
Defaulting open is the normal, safe outcome. The differential behaves like an ordinary one: traction is lost on loose or slippery ground, the vehicle drives entirely normally on tarmac, and nothing is at risk. That is most cases.
Defaulting engaged is the case worth knowing about, because it is uncomfortable and gets misdiagnosed. A front differential that stays locked makes the vehicle bind, judder and skip its front tyres through a tight turn — the two front wheels are being forced to the same speed while geometry demands different ones. That is routinely investigated as a constant velocity joint, a gearbox fault or a seized brake, and it is none of them.
So the free test is a full-lock circle at walking pace on dry tarmac. Binding and hopping that appears only on tight lock and disappears when the wheel is straightened is a differential that has not released.
If it does bind, drive it as little as possible — the tyres and the driveline both take the load — and mention it, because it changes what should be looked at first.
Likely causes
Start here
- Corroded or loose connector · easy
- Damaged wiring harness · moderate
- Water ingress into the module connector · moderate
- Physical damage from road debris · moderate
Less common
- Blown fuse or failed supply · easy
- 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 U0135.