P2593: Turbocharger Speed Sensor B Circuit
What to do
Expect the engine to feel down on power, and that limiting is deliberate — without a speed signal the module has no way of knowing whether the turbocharger is approaching a speed that would destroy it, so it holds boost back. Driving gently to a workshop is fine.
Describe when the power disappears, because it identifies which turbocharger this is about. If the car pulls normally from low speed and then simply stops gaining higher up, that points at the second unit of a sequential pair and saves diagnostic time.
The fault is usually wiring or a connector rather than the sensor — this loom runs against a housing full of exhaust gas, and on a twin-turbo engine there are two of them in a crowded bay. A code here says nothing about the condition of the turbocharger itself, so ask what has actually been tested before agreeing to one.
What this code means
A fault in the circuit of the speed sensor on the second turbocharger.
What a turbocharger speed sensor is, why only some engines have one, and why it is a protective instrument before it is a control input are all set out at P2578. The distinction here is the letter, and it means the vehicle has two turbochargers.
Which one is B follows the same convention as the position sensors at P2586: on a parallel installation, normally the unit on the bank that does not contain cylinder 1; on a sequential installation, normally the larger, higher-speed unit that takes over as flow rises.
On a sequential system that makes this the more important of the two sensors, not the less. The staged arrangement exists so that a small turbocharger can handle low engine speeds and hand over to a large one — and the unit doing the high-speed work is the one operating nearest its mechanical limit. Losing speed feedback there removes the protection where the margin is thinnest.
With no usable signal the module caps boost, so the engine feels flat. On a sequential system that flatness may be confined to the upper half of the rev range, because the second turbocharger is barely involved below it — a car that pulls normally from low speed and then simply stops gaining is a much better description of this code than a general lack of power.
The electrical causes are identical to P2578, and on a twin-turbo engine the heat problem is worse: two turbine housings glowing in one bay leave less air and less room around the looms routed past them.
Likely causes
Start here
- Corroded or loose connector · easy
- Heat damage to sensor or wiring · moderate
- Faulty turbocharger speed sensor · moderate
- Damaged wiring harness · moderate
Less common
- Failed sensor reference voltage supply · moderate
Symptoms
Components involved
Information, not instruction
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Community experience
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