P2594: Turbocharger Speed Sensor B Circuit Range/Performance

P2594 means the second turbocharger speed sensor produces a signal, but its reported speed does not agree with what the engine computer predicts for that turbo. Bentley documents it on the W12 in the Continental GT/GTC, Flying Spur and Bentayga (bulletin 2053348, versions 5 and 10): after a smoke test of intake and exhaust, a detached divider inside the air filter box on Continental and Flying Spur turned out to be one cause; with symptom code 23179 alone the code is cleared and retested without parts, while symptom code 32790 leads to a new speed sensor. P2593 and P2595-P2597 are circuit faults of the same sensor, P2579 the matching fault on sensor A. The warning lamp comes on.

Symptoms

• Malfunction indicator lamp on
• Fault often appears only under particular load or gradient conditions
• Turbo speeds of both banks differ noticeably in live data

Most likely causes

• Speed sensor B delivering an implausible signal
• Detached divider in the air filter box disturbing the flow to one turbo
• Intake or exhaust leak on the bank of the second turbo

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the hoses, clamps, and intercooler
2. Compare the reading with other engine data while varying the engine speed.
3. Compare commanded and actual pressure in live data
4. Check the actuator's movement
5. Check the vacuum hoses and the solenoid valve
6. Check the oil and the turbo shaft play before replacing it

Good to know

• Repair difficulty: hard
• It can trigger limp mode.
• It affects emissions.

What each character of P2594 means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• 5: Speed and idle
• 94: Specific fault in that system

Frequently asked questions

Can I keep driving with code P2594?

Drive without demanding power and go to a repair shop soon. If you see a lot of blue smoke or hear a metallic noise, shut off the engine.

What causes code P2594?

The most common causes are: speed sensor B delivering an implausible signal; detached divider in the air filter box disturbing the flow to one turbo; intake or exhaust leak on the bank of the second turbo.

Related codes

• P2593Turbocharger Speed Sensor B Circuit
• P2595Turbocharger Speed Sensor B Circuit Low
• P2596Turbocharger Speed Sensor B Circuit High
• P2597Turbocharger Speed Sensor B Circuit Intermittent
• P2579Turbocharger/Supercharger Speed Sensor A Circuit Range/Performance

Sources

• static.nhtsa.gov: MC 10203225 0001
• static.nhtsa.gov: MC 10228850 0001
• law.cornell.edu: 13 CCR 1968.2

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.