P259D is the turbocharger B version of the closed-loop timing fault. On engines with two separately regulated chargers, the control unit expects the boost regulation of the second unit to switch to feedback operation within a set time, and here it did not. No manufacturer documents P259D publicly with thresholds; the basis is CARB 13 CCR 1968.2, which asks for a malfunction when feedback boost control does not start in time or falls back to default operation. GM's 2018 diesel table illustrates the dependency on the A side: its actuator plausibility checks only run while VGT position feedback is active and no fault is present on the position sensor or the actuator circuit. A stored sensor or actuator fault on charger B is therefore the first thing to repair. P259C covers turbocharger A.
Medium severity. Can I keep driving?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.
Symptoms
- Engine warning lamp on
- Reduced power, especially at higher load
Most likely causes
- Fault on position or pressure sensing for charger B
- Actuator B or its control circuit faulty
- Leak in the charge air path of charger B
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
- It can trigger limp mode.
- It affects emissions.
What each character of P259D means
- P: Powertrain: engine and transmission
- 2: Generic code: same on every make
- 5: Speed and idle
- 9D: Specific fault in that system
Frequently asked questions
Can I keep driving with code P259D?
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 P259D?
The most common causes are: fault on position or pressure sensing for charger B; actuator B or its control circuit faulty; leak in the charge air path of charger B.
Related codes
- P259CExcessive Time To Enter Closed Loop Turbocharger A Boost Control
- P2587Turbocharger Boost Control Position Sensor B Circuit Range/Performance
- P2586Turbocharger Boost Control Position Sensor B Circuit
Sources
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.