P0249
Turbo/Supercharger Wastegate Solenoid B Low
The appearance of the standard OBD2 trouble fault code P0249 is an indicator that your vehicle ECU triggered a threshold alert for "Turbo/Supercharger Wastegate Solenoid B Low". Understanding the root component breakdown helps avoid expensive diagnostic fees.
Driver's Summary
Code P0249 means your vehicle detected a problem with the turbo/supercharger wastegate solenoid b low system. On the road, this usually shows up as constant underboost, limp mode. This is not a code to ignore — the underlying fault can rapidly worsen and lead to costly repairs if driving continues.
Symptoms
Constant underboost, limp mode
Common Causes
- Short to ground in solenoid B circuit
- Failed solenoid B
- Wiring harness short
- Failed PCM
How to Fix
- 1 Repair short to ground
- 2 Replace wastegate solenoid B
- 3 Repair wiring harness
- 4 Replace PCM
Technical Explanation
The PCM triggers P0249 after its internal monitoring routine detects that a specific circuit or sensor has exceeded its acceptable operating range. The PCM monitors crankshaft rotational velocity via the CKP sensor at a resolution of individual tooth gaps on the reluctor ring. A combustion event in each cylinder produces a measurable acceleration spike; its absence or weakness is flagged as a misfire event within a 200-revolution or 1000-revolution test window. After two failed drive cycles, the code transitions from a pending to a confirmed DTC, and the PCM activates the MIL. Clearing the code without repairing the fault will result in re-illumination within one to two complete drive cycles.
Is It Safe to Drive?
This fault carries real mechanical risk. The root causes — including short to ground in solenoid b circuit — can trigger a chain reaction of component failures if the vehicle continues to be driven. Have it towed or drive directly to a shop without delay.
Mechanic's Pro Tip
Before replacing any component on P0249, spend 5 minutes inspecting the wiring harness and connector first — corrosion, chafed insulation, and backed-out pins cause the majority of these faults and cost nothing to fix. Use a multimeter to measure voltage drop across the connector pins under load; anything above 0.1V indicates excessive resistance that will cause intermittent failures even after replacing the sensor.
Solenoid: 80 - 200