P259E: Turbocharger A Boost Control Position At Low Limit

P259E means the boost control of turbocharger A has run out of range at the low end: the actuator is at its limit, yet boost stays well under the target. Ford's 2023 diesel OBD summary places it in the underboost monitor. With closed-loop boost control active, at least 50 Nm (6.7 L) or 135 Nm (3.0 L) and 800 or 1300 rpm, it sets when desired boost exceeds actual boost by more than 120 kPa (6.7 L) or 80 kPa (3.0 L) for roughly 10-11 s. Ford's special service message 50564 for 2020-2022 Super Duty 6.7 L lists P259E among turbo-related codes and makes the variable vane actuator available on its own, so the whole turbocharger need not be replaced. P259F is the opposite limit, P2263 the slower general boost performance check, P0299 plain underboost.

Symptoms

• Engine warning lamp on
• Clear loss of power under load
• Whistling or hissing from the charge air side

Most likely causes

• Leak in charge air pipes, intercooler or clamps
• Variable vane actuator or vane mechanism not reaching the commanded position
• Exhaust leak upstream of the turbine
• Boost pressure sensor reading too low

What to check, in order

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

1. Check the hoses, clamps, and intercooler
2. With the connector unplugged, check whether the signal wire is making contact with ground.
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: medium
• It can trigger limp mode.
• It affects emissions.

What each character of P259E means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• 5: Speed and idle
• 9E: Specific fault in that system

Frequently asked questions

Can I keep driving with code P259E?

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 P259E?

The most common causes are: leak in charge air pipes, intercooler or clamps; variable vane actuator or vane mechanism not reaching the commanded position; exhaust leak upstream of the turbine.

Related codes

• P259FTurbocharger A Boost Control Position At High Limit
• P25A0Turbocharger B Boost Control Position At Low Limit
• P2263Turbocharger/Supercharger A Boost System Performance
• P0299Turbocharger/Supercharger A Underboost Condition
• P2598Turbocharger Boost Control Position Sensor A Performance - Stuck Low

Sources

• fordservicecontent.com: obd summary diesel 2023
• static.nhtsa.gov: MC 10208834 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.