U0134: Lost Communication With Power Steering Control Module — Rear
What to do
Drive gently and pay attention to whether the car feels straight.
Your car steers with its rear wheels as well as its front ones — a few degrees, opposite to the fronts at low speed to tighten the turning circle, and with them at speed for stability. This code means the computer doing that has stopped talking to the rest of the car.
Normally the car centres the rear wheels and locks them, and then behaves like an ordinary car. Two things follow.
The first is only surprising: your turning circle has just got much bigger. If you are used to how tightly this car turns, you will misjudge the first car park or three-point turn. Allow for it.
The second matters. If the rear wheels did not centre properly, the car will track slightly sideways, pull under braking, and scrub its rear tyres out within a few hundred miles. If the car does not feel like it is going straight, or is not following the line you are steering, stop and have it recovered rather than driving it home.
One thing to insist on when it is repaired: a four-wheel-steering car needs its rear axle aligned with the proper procedure and equipment. A workshop that treats it like an ordinary alignment can hand it back driving worse than it arrived.
What this code means
The rear steering module has stopped being heard from. The general reasoning is at U0100, and U0435 covers the same module reporting implausibly instead.
This is rear-wheel steering, and the first thing worth establishing is that it is not a minor convenience. The rear wheels turn by a few degrees — opposite to the fronts below about 40 km/h, which shortens the turning circle dramatically, and with the fronts above it, which is what makes a long vehicle change lane calmly at speed.
When the module goes silent the system must centre the rear wheels and lock them there, and a correctly working failsafe does exactly that. The vehicle then behaves like a conventional one.
Two consequences follow, and they are opposite in character.
The harmless one is the turning circle, which becomes suddenly and markedly larger. A driver who has learned the car's tight manoeuvring will misjudge a car park or a three-point turn on the first attempt — surprising rather than dangerous, but worth knowing before reversing into something.
The one to take seriously is a rear axle that has not centred. If the wheels were turned when communication was lost and the failsafe did not bring them back, the vehicle crabs: it tracks slightly sideways, pulls under braking, and wears its rear tyres visibly within a few hundred miles. If the car does not feel straight, is not behaving predictably, or is following a line other than the one the wheel asks for, stop and have it recovered rather than driving it home.
One thing to insist on afterwards. A four-wheel-steering vehicle cannot be aligned like a conventional one — the rear axle has its own geometry and its own procedure, and a workshop without the equipment for it can leave a car that drives worse than it did.
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
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Community experience
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