Mercedes CLS Turbo Actuator Repair — 320 CDI and 350 CDI (W219)

This page is for the owner of a CLS 320 CDI or 350 CDI that has gone flat, dropped into limp mode, or stored a 2510 boost pressure control fault that a garage has quoted a complete turbocharger to cure. The part that usually causes it unbolts from the side of the turbo and travels in a padded envelope — but only once it has been identified correctly, which on this car is the whole difficulty.

Which CLS Actuator Are You Actually Holding?

The CLS is not a one-reference car, and that is where the money goes astray. Four actuator reference combinations are listed against the same 3.0-litre CLS, split by build period, and two of them share a Hella number with each other. Read the codes off your own unit before you order, search or send anything — they are printed or moulded into the plastic top section, on the face turned away from the turbocharger.

Why 712120 on its own tells you almost nothing

712120 is the number CLS owners most often find and quote, and alone it is close to useless. It is a base reference: it confirms a Hella actuator and no more. The same 712120 is listed against the E220 CDI unit carrying G-107, the E320 3.2 CDI unit carrying G-187 and the 3.0 V6 unit carrying G-219 — three different actuators, for three different turbochargers, sharing one number.

That reach matters most if you are buying second-hand. The 3.0 V6 actuator also turns up under the E280 and E320 CDI, the C320 CDI, the ML320, the R320, the Vito and the Sprinter, so a unit described as “a Mercedes 3.0 actuator” tells you the engine range it came from, not whether it will control your turbo. If the clearest markings on your label are short two- or three-character codes, those are not fitment references — photograph the label and send it with your registration.

What a Failing CLS Actuator Does

When the actuator can no longer put the vanes where the engine control unit asks, the boost the engine receives stops matching the boost it is being fuelled for. Everything the driver notices follows from that mismatch.

Power loss under acceleration. The commonest complaint, and worst where the engine is asked to work — a junction, a motorway gradient, a loaded car. A loss of power that is permanent rather than occasional generally points inside the actuator itself: the motor, the gear train, the position sensor or the circuit board.

Power loss that comes and goes. Full power returns for a while, often after a restart, then the fault comes back. Worth confirming rather than assuming, because a vane mechanism that sticks and frees as it heats and cools produces much the same effect.

Juddering, smoke and the engine management light. Fuelling and boost falling out of step. Smoke under acceleration usually arrives alongside the power loss rather than ahead of it.

Limp mode. The protection, not the fault: the gap between commanded and delivered boost has passed what the control unit will tolerate, so it holds the engine at a fixed, reduced output.

An arm that will not move. The end-stage symptom and the most conclusive on the list. It means either the actuator can no longer drive, or what it drives has seized solid.

Fault Code 2510, and What a Generic Reader Shows Instead

Mercedes-specific equipment usually stores 2510 – Boost Pressure Control, sometimes written 2510-001. Read what it actually says: the control unit did not get the boost it asked for. That describes the system, not the component, and it does not distinguish a failed actuator from a seized nozzle ring or a leak upstream. A generic OBD-II reader often cannot see the Mercedes-side code at all and returns a plain boost code instead — P0299 underboost, P0234 overboost, P2263 boost system performance.

Two details are worth more than the code number itself, so record them before anything is disturbed: whether the fault stays stored or clears on an ignition cycle, and what the car was doing when it appeared — cold, hot, under load, at idle. Send that in with the unit and it gets read against what the bench test finds.

One thing to disregard: any published code list that puts P132A or P132B against a CLS. Those are Ford codes, reused onto Mercedes pages from a single list covering every make, and a CLS will never store either.

Actuator or Turbocharger? The Check That Separates Them

Two entirely different faults produce the same symptoms and the same code, and they are not comparable jobs. One is a small unit that unbolts and goes in the post. The other means the turbocharger comes out of the vee of the engine.

Start with the engine running and watch the actuator’s operating arm as the engine is revved: on a healthy system it moves as the vanes are commanded. If it does not move at all, you have narrowed the fault to two candidates — but not yet separated them.

The check that does separate them is made with the actuator unbolted. Move the operating arm through its full range of travel by hand. If it sweeps freely end to end with no sticking, the nozzle ring is moving as it should and the actuator is your suspect. If it binds, catches part way or will not move, the vane mechanism inside the turbine housing has seized and no work on the actuator will cure the car — that is a job for our turbo repair and rebuild service, or our Garrett GT2052V turbo repairs for the same component-level approach applied to a Garrett variable-geometry unit.

One practical note: on the 3.0 V6 the turbocharger sits in the vee between the cylinder banks, so access is tight and this is not a kerbside job. Any competent independent garage can get the actuator off, and the actuator is all we need.

Why the Quote Is Always for a Complete Turbocharger

Nothing about the engineering makes this an expensive fault. The way the part is supplied does. Mercedes-Benz does not list the electronic actuator as a separate item, so a franchised dealer can only quote a complete turbocharger with an actuator attached, plus the labour to get it in and out of the vee — a serviceable turbocharger scrapped to reach a failed sub-assembly bolted to its side. That leaves three routes, and they are not equal.

A used actuator looks cheapest and is the weakest of the three. It has already travelled some unknown distance down the same road as yours, it has to be matched on the G-code rather than the base number to control your turbo correctly, and used units generally require coding to the vehicle before they will work at all.

A reconditioned exchange unit is quicker, because a rebuilt actuator is already on a shelf. The trade-off is that whatever arrives still has to be matched to your turbocharger, while the one unit you know for certain is correct — the one that came off your car — has gone the other way.

Rebuilding the unit you already own removes the fitment question altogether, because the part going back on is the part that came off. Your turbocharger stays where it is. Repairs start from £100, turnaround is typically one to two working days, nothing needs coding on refit, and every rebuild carries a lifetime, unlimited-mileage warranty. Where a core is genuinely beyond rebuilding, replacement turbochargers live in our shop.

Our Mercedes CLS Actuator Rebuild

A CLS actuator does its work in the vee of the engine, between two cylinder banks — about the least forgiving place on the car to put a small motor and a circuit board. So we rebuild it for that environment rather than merely back into it: the components heat takes out first are renewed rather than refitted, and the unit has to hold a stable, repeating position reading once it is warm before it is signed off.

It is a mail-in service, run from our own workshop at Unit 102 Reaver House, 12 East Street, Epsom, Surrey, KT17 1HX, United Kingdom, by turbo specialists and electronic engineers who work on these units daily. The CLS never leaves your driveway. There is more on the workshop on our about page.

1. Take the actuator off and send it in. It unbolts from the side of the turbocharger and the turbo stays on the vehicle. Complete the online repair form with your registration, whether the car is a 320 CDI or a 350 CDI, the codes stored, every reference off the housing and what the hand check showed.
2. Pack it to survive the journey. Bubble wrap or foam inside a rigid box; paper and cloth offer no real protection to the plastic housing or the connector.
3. We test it before we open it. The unit goes on the bench first, so what we find is what has genuinely failed rather than what was assumed to have failed — and occasionally so we can tell you there is no work here worth paying for.
4. We rebuild it at component level. Motor and brushes, reduction gears, position sensor and seals renewed as required, the circuit board reworked, and components with a known weakness in the original design uprated, so the rebuilt unit meets or exceeds original specification.
5. We calibrate it, prove it and return it. The unit is cycled through its full travel and checked against live boost targets before sign-off, then comes back ready to bolt straight on — no dealer visit, no coding, no setting up on the car.

Units are accepted from anywhere in the UK and internationally; if you are sending from overseas, get in touch before posting and we will confirm the arrangements first. The full range is on our electronic turbo actuator repair service.

Mercedes CLS Turbo Actuator Repair FAQ

Final Thoughts

What goes wrong on a CLS is rarely the diagnosis. It is the identification. The symptoms are consistent, the 2510 code is unambiguous about the system it describes, and the hand check settles the actuator-or-turbocharger question in a couple of minutes. Then the job runs into four reference combinations for one car, a base number that identifies nothing on its own, and a whole family of Mercedes 3.0 diesels wearing similar-looking units.

So do the reading before the spending. Photograph the label, note whether the fault stays stored or clears, and sweep the arm by hand once the unit is off. Those three things cost nothing but a little time, and between them they tell you — and tell us — most of what there is to know about the job in front of you.