VW T5, T6 and Amarok Ignition Switch Failures: Why The Steering Lock Housing Is Usually The Real Fault
Every VW commercial vehicle workshop in the country has seen the same problem. Customer turns the key, dashboard lights up halfway, nothing happens. Or the dash lights normally but the starter does not engage. Or, oddest of all, the van starts and runs fine but the radio and electric windows are dead. The owner thinks the battery is on the way out. The auto-electrician thinks the immobiliser. Most of the time, both are wrong. The fault is the steering lock housing assembly that contains the ignition switch contacts. This guide is the workshop view: how to diagnose it, why it fails on T5, T6 and Amarok specifically, and what to fit when it does.
The architecture, briefly
On the affected VW commercial vehicles, the ignition is not a single switch behind the key. It is a multi-part assembly: a mechanical steering lock barrel, a microswitch sled that tells the BCM where the key is, and a power switching block that distributes 12 V to different circuit groups depending on key position. The part number 6R0905851F (and its variants across model years) is the housing assembly that contains all of this.
The component is shared across a large group of VAG products, but the failure pattern is most prominent on commercial vehicles because they see more thermal cycling, more dirt, and more vibration than passenger cars. A T5 used for daily multi-drop deliveries can put 100,000 cycles on the ignition switch within five years. By 200,000 cycles the internal contacts are noticeably worn.
The three failure modes
The housing fails in three distinct ways, often progressively on the same vehicle:
Mode 1 — worn contacts on one circuit group. The key turns to position 2 (ignition on), most of the dash lights up, but some specific group of accessories (commonly the radio circuit or the heated rear window) stays dead. The customer often does not realise the rest of the vehicle is also affected because the parts they use most are still working.
Mode 2 — intermittent no-start. The key turns to position 3 (crank), the starter does not engage. Try again, it cranks fine. The microswitch sled position is no longer reliable. This is the most common reason these vans turn up on a recovery truck.
Mode 3 — stuck contacts in position 2 after key removed. Key turns to OFF, key comes out, but the van's dashboard is still partially live. Battery flattens overnight. Often misdiagnosed as a parasitic drain from elsewhere when the source is actually a stuck position-2 contact in the ignition assembly.
The diagnostic path
The temptation when faced with a no-crank is to chase the starter circuit. Check the battery, check the cable, check the solenoid feed, check the engine ECU crank-request. On these vans, the better first step is to scope or back-probe the ignition switch output at the BCM. If the key is at position 3 and the switch output is missing the corresponding signal, the switch is the fault and no amount of starter circuit testing will help.
For Mode 1 (specific circuit group dead), use a wiring diagram to identify which circuit is missing, then trace it back to the ignition switch terminal that should be driving it. A meter at the right terminal during key-on tells you whether the switch is delivering the voltage; if not, the contact internal to the switch has worn open. This is rarely diagnosable from outside the housing.
For Mode 3 (key off but accessories live), pull fuses one at a time until the residual current at the battery drops to zero. The fuse that solves it is on the circuit being held live by the failed contact. Confirms ignition switch fault and identifies which contact group has failed.
Coding, immobiliser and the key
The thing that makes this job different from a simple ignition switch on an older vehicle is the immobiliser interaction. The replacement housing assembly contains a new microswitch sled, but the immobiliser system on these vans uses a transponder ring antenna integrated into the housing. Fit a new housing without the right coding step and the engine will crank but not start.
The right procedure involves either programming the new housing's ring antenna to recognise the existing keys (which requires VAS / ODIS dealer-level access on most years) or, in some workshop-friendly cases, swapping the original ring antenna across from the old housing to the new one. The ring antenna part is the bit that holds the immobiliser secret; the rest of the housing is a mechanical and electrical assembly without security implications.
Workshops doing these jobs regularly invest in the coding tool or have a standing arrangement with a coding specialist. The labour to fit the new housing is straightforward; the coding step is the bit that can leave a van off the road for an extra day if not planned.
Why T5, T6 and Amarok specifically
The same housing assembly appears across a much wider VAG fleet, but the failure rate is highest on T5, T6 and Amarok because of usage patterns. These vehicles do daily heavy-duty work: cycling the ignition tens of thousands of times a year, vibrating through rough roads and unsealed surfaces, sitting outdoors in all weather. The same component on a Golf or Polo used for a 20-mile commute fails far less often because it is asked to do less.
The other factor is dust and grit ingress. The lower steering column on a commercial vehicle is closer to the dirty work the driver is doing: boots in and out of the cab with mud, dropped tools, spilled coffee. Over years that ingress works its way into the housing and contributes to the wear.
What to fit
The OE part is part number 6R0905851F (subject to confirmation against the VIN; later model years have superseded part numbers). Our VW T5/T6/Amarok steering lock housing ignition starter switch is the direct replacement and includes the full mechanical and electrical assembly. The fitment requires the standard removal procedure for the steering column shroud, disconnection of the battery, careful handling of the airbag harness routing, and then four bolts and two connectors to drop the assembly out.
One thing to watch on the install: the new assembly's microswitch sled has a specific alignment to the steering column casting. Force it into position without confirming the alignment marks line up and the switch will operate but the key-position feedback to the BCM will be wrong, which produces an entirely new set of intermittent faults. Take the extra two minutes to confirm alignment before tightening down.
The trim clip warning
Getting to the steering lock housing requires removing the steering column shrouds (upper and lower), which on T5, T6 and Amarok involves several plastic trim clips that are notorious for snapping if forced. Workshops that do these jobs regularly keep a small stock of replacement trim clips on the shelf. Our VW Volkswagen-specific 130-piece trim clip assortment kit covers most of the common clip types you will encounter on these vans, including the steering column shroud retention clips, the dashboard end-cap clips, and the underdash trim clips you have to remove to access the ignition area.
The customer conversation
This is a job worth explaining to the customer. The labour cost is meaningful, the coding cost is meaningful, and there is no way to make a worn-out ignition switch cheap. What is worth pointing out is the alternative: a van that keeps stranding the driver, costs in lost work hours, missed deliveries, and (eventually) a recovery bill that adds up to more than the repair. Fixing the ignition switch properly is a one-off cost. Living with the failing one is a recurring tax.
Customers who understand that calculation pay for the proper repair without complaint. Customers who are not given the full picture sometimes look for a cheaper bodge from somewhere else and end up paying twice. The honest conversation is the right one to have.
Closing thought
The VW T5/T6/Amarok steering lock housing failure is one of those quiet jobs that workshops with the experience handle in a half-day and workshops without that experience end up chasing for two weeks. The diagnostic is straightforward once you know the failure modes; the parts are available; the coding is manageable. The vans need this work done as they accumulate miles, and the customer is well-served by a workshop that has seen it before, recognises the symptoms, and quotes the job honestly the first time.
