P2586: Turbocharger Boost Control Position Sensor B Circuit
What to do
Expect the engine to feel flat, possibly with a reduced power warning. It is not usually damaging, so driving gently to a workshop is reasonable.
The important thing to establish is which turbocharger this code is about, because your car has two and the labour to reach them differs enormously. On a V engine, B is normally the one on the bank that does not contain cylinder 1 — worth confirming for your specific engine before anything is taken apart, since guessing wrong means dismantling the wrong side.
If your car has a small turbo and a large one working in sequence, describe when the problem shows up. A fault on the second unit often appears only at higher speeds — fine around town, flat on the motorway. That detail identifies the code quickly and is worth volunteering.
And as at P2562: this code names the turbocharger, but the sensor, the actuator and carbon binding the vanes are all far commoner and far cheaper than a turbocharger. Ask what has been ruled out before agreeing to a replacement.
What this code means
A fault in the circuit of the position sensor on the second turbocharger's boost control mechanism.
The letter is the whole story of this code. What the sensor is, what the vanes do and why their position must be measured are all set out at P2562, and none of it differs here. What differs is that this code only exists on a vehicle with two turbochargers — so before anything is measured, the question is which one B refers to.
There are two arrangements and they fail differently.
Parallel twin-turbo is the usual arrangement on a V engine: one turbocharger per cylinder bank, both doing the same job at the same time. Here B is normally the unit on bank 2 — and bank 2 is defined as the bank that does not contain cylinder 1, which is not reliably the same as "the far side" or "the passenger side" across manufacturers. Getting that wrong means dismantling access to the wrong turbocharger, which on a V engine is most of the labour in the job. Confirm the bank convention for the specific engine before anything is removed.
Sequential twin-turbo puts a small turbocharger and a large one in series, staged: the small one supplies boost from low engine speed, and the large one takes over as flow rises. The two are switched between by control valves. Here B is usually the larger, higher-speed unit — and because it only works hard at higher engine speeds, a fault on it can be invisible in town driving and appear only on a motorway. A complaint of "fine around town, flat above 3,000 rpm" fits this code far better than a general lack of power does.
That staging also adds a failure mode with no equivalent on the A side: the changeover valves themselves. A vane position code on the second turbo of a sequential system is worth checking against the changeover control before the turbo is blamed, because a unit that is never properly brought online will not respond to position commands in the way the module expects.
The electrical causes are identical to P2562 — heat-damaged wiring, a chafed conductor against a red-hot housing, a corroded plug — and the module's response is the same: without trustworthy feedback it defaults the vanes and accepts low boost.
Likely causes
Start here
- Corroded or loose connector · easy
- Faulty turbocharger vane position sensor · moderate
- Damaged wiring harness · moderate
- Heat damage to sensor or wiring · moderate
Less common
- Faulty turbocharger vane actuator · specialist
- Failed sensor reference voltage supply · moderate
Symptoms
Components involved
Information, not instruction
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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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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
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