U010C: Lost Communication With Turbocharger/Supercharger Control Module A
What to do
Expect reduced power, and possibly limp mode. The engine is protecting itself: without confirmed control of the turbocharger it will not risk boost, so what you have is a deliberately weakened engine rather than a damaged one. It is drivable, gently, to somewhere it can be looked at.
Ask for the wiring, the connector and the module's supply to be checked before the actuator or the turbocharger is quoted for. On most engines the part this code names sits on the turbocharger itself — the hottest place under the bonnet — and its connector and wiring fail far more often than the electronics inside it. The part is expensive and is sometimes only sold with the turbocharger attached.
If it is replaced, ask whether it has been calibrated to this turbocharger. A new actuator that has not learned its own limits reports meaningless positions, and the fault looks like it survived the repair.
What this code means
The module controlling boost has stopped being heard from on the data network. What a lost communication code does and does not mean is at U0100 and applies here unchanged.
The surprise in this code is that many vehicles carrying it have no separate boost computer at all, and it still applies to them. The turbocharger's vane actuator on most modern diesels is itself a module — a small sealed unit with its own processor, addressed over a LIN or CAN line, which receives a target position as a message and reports back where it actually is. It is not a motor taking a voltage. That is why losing the conversation with it produces a communication code rather than a circuit code.
An electric supercharger or an electrically assisted turbocharger is the other case, and there the module is a genuinely substantial one, running a motor on the 48 volt system.
What the engine does next is the safe thing, and it is why this reads as a serious fault from the driver's seat. With no confirmed control of boost, the module has no way to prevent an overboost, so it commands the fail-safe position and limits torque: reduced power, no meaningful boost, and usually limp mode.
The diagnostic point is the one this corpus makes about every module a code names. The actuator is expensive, frequently sold only as part of the turbocharger, and is usually innocent — its supply, its earth, its connector and the single wire carrying the conversation account for most of these. The connector's position is against the argument for the actuator too: it lives on the turbocharger, which is the hottest thing on the engine, and heat is what ages a connector.
If the actuator genuinely is replaced, it must be calibrated to the turbocharger it is fitted to. A new one that has not learned its own end stops reports positions that mean nothing, and the fault appears to persist through the repair.
Likely causes
Start here
- Corroded or loose connector · easy
- Damaged data bus wiring · moderate
- Failed power or earth supply to the module · moderate
Less common
- Damaged wiring harness · moderate
- Actuator not calibrated after repair · specialist
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
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