Can a bad ground cause a circuit-high code?

Yes, and on these solenoids it is the cause most often missed. Wastegate solenoids are typically ground-side switched, meaning the coil has battery voltage on one side continuously and the module turns it on by pulling the other side to ground. When the module commands the solenoid on, the control-wire voltage should drop. If the ground has corroded or picked up resistance, the module cannot pull that voltage down, so the wire stays high and the module reports a circuit-high fault with a perfectly good solenoid. Test the ground for low resistance under a small load, because a corroded ground will pass a simple continuity check and still fail once current flows.

How is P0250 different from P0249?

They are opposite directions on the same circuit. P0250 means the module found voltage on the circuit when there should not have been any, which points at a short to voltage, a poor ground on a ground-side-switched solenoid, or an internally shorted coil. P0249 means the module found no voltage where it expected some, which points at a short to ground, an open circuit, a blown fuse, a bad connector, or an open coil. The two lists barely overlap, so the single most efficient thing you can do is confirm which code you actually have before you pick up a meter.

Should I swap the "A" and "B" solenoids to see if the fault moves?

It is tempting, and on many circuits it would be sensible, but here it carries a real risk. Some platforms fit different valves in the "A" and "B" positions, and installing the wrong one gives you an induced fault stacked on top of the original one with no clean way to separate them. You can get the same information without that risk: measure both solenoids' coil resistance, compare connector condition and pin fit, and command each one with a scan tool while watching control-wire voltage. If you do decide to swap them, confirm the part numbers match first.

Is a short to voltage hard to find?

It takes patience but it is tractable, because the fault is physical. A wire cannot short to voltage without touching something energized, so there is damage to locate. Follow the harness the whole way from the module connector to the solenoid, looking for shiny or flattened areas where it has rubbed against a bracket, pinch points under clamps, and melted or discoloured insulation where it has rested against the turbo or exhaust manifold. Then wiggle-test the run while watching control-wire voltage with a meter. Intermittent shorts usually reveal themselves the moment you move the section that is failing.

OBD-II trouble code

P0250: Turbocharger/Supercharger Wastegate Solenoid "B" High

The module found voltage on the second wastegate solenoid circuit when there should have been none. A short to voltage will do it — but so will a corroded ground on a solenoid that is switched on the ground side, which is the cause most often missed.

Medium severityPowertrainFuel & AirDrivable short-term

Quick facts

System: Powertrain
Category: Fuel & Air
Severity: Medium severity
Drivable: Usually safe to drive short-term
Repair cost range: $110 – $1,000
DIY difficulty: Intermediate DIY

What does P0250 mean?

P0250 is the circuit-high member of the wastegate solenoid "B" family and the exact mirror of P0249. Where P0249 sets because the module found no voltage on the circuit when it expected some, P0250 sets because the module found voltage already applied to the circuit when there should not have been any. Reading which of the two you actually have before you start testing is the difference between a short diagnosis and a wasted afternoon, because the suspect lists barely overlap.

The first cause is a short to voltage. If the control wire touches an ignition feed, a battery feed, or another energized circuit anywhere along its run, the module sees that voltage sitting on its output and reports it. The useful thing about this cause is that it is physical and therefore findable. A wire cannot short to voltage without contacting something energized, so there is damage somewhere: chafed insulation where the harness crosses a bracket edge, a flattened section that has been pinched under a clamp, a spot melted where it rested against something hot, or a connector where two circuits have shorted through corrosion or water. Follow the harness, look for shiny, flat, or discoloured areas, and wiggle-test the run while watching for the fault to appear.

The second cause is the one that catches people out. These solenoids are typically ground-side switched: the coil sees battery voltage on one side all the time, and the module completes the circuit by pulling the other side to ground. That means when the module commands the solenoid on, the voltage on the control wire should DROP. If the ground path has corroded or developed resistance, the module cannot pull that voltage down — the wire stays high, and the module reports a circuit-high fault even though the solenoid itself is in perfect condition. Test the ground for low resistance under a small load rather than trusting a continuity beep, because a corroded ground will pass a continuity test and still fail the moment current flows through it.

Because this is the "B" circuit, two contextual facts shape the job. First, if both P0250 and its "A" counterpart P0246 are stored, look at what the two circuits share before condemning either solenoid — a common power feed, a relay, or a shared ground will code both sides at once, and one repair clears both. Second, the "B" solenoid is usually the physically harder one to reach, typically serving the rear turbo on a transverse engine or the far bank on a longitudinal one. That does not change the electrical diagnosis, but it does change the labor estimate substantially, and it is worth establishing which valve is "B" before anyone quotes the job.

One shortcut to avoid: swapping the "A" and "B" solenoids to see whether the fault follows. It sounds efficient, and on a code like this it is tempting. But some platforms fit different valves in the two positions, and installing the wrong one creates a second problem stacked on top of the first — now you have a real fault and an induced one, and no clean way to tell them apart. Compare the two solenoids by measurement instead: coil resistance, connector condition, and commanded behaviour on a scan tool all give you the same information without disturbing a working component.

The driver experience is the familiar one for this family. Without trustworthy boost control the module defaults to a safe state — wastegate open, minimal boost, reduced power — so the car drives but feels as though the turbo has stopped contributing. On a twin-turbo engine that may present as an imbalance rather than uniform flatness. It is protection, not mechanical failure, and full power returns once the circuit is repaired.

Common causes

Control wire shorted to voltage — to an ignition feed, battery feed, or another energized circuit
Corroded or high-resistance ground on a ground-side-switched solenoid, so commanded voltage never drops
Chafed insulation where the harness crosses a bracket edge or bulkhead
Harness section flattened or pinched under a clamp
Insulation melted where the harness has rested against the turbo, exhaust manifold, or another hot surface
Corroded or water-intruded connector allowing two circuits to short together
Failed "B" wastegate solenoid with an internally shorted coil
Wrong solenoid fitted in the "B" position from a previous repair or a swap attempt
Shared power feed or relay fault — normally sets the "A" code alongside this one
PCM solenoid driver fault, rare and diagnosed only after everything else checks out

Symptoms

Check engine light with P0250 stored
Noticeable loss of power — the engine feels like the turbo is not contributing
Reduced-power or limp mode
Uneven boost between the two turbochargers or banks in live data
Boost target and actual boost diverging in live data
Poor acceleration and slow throttle response
Hesitation or a rough handover on sequential-turbo systems
Reduced fuel economy
Abnormal exhaust smoke on some diesel applications
Additional codes at the same time if a shared ground or power feed has failed

Diagnostic steps

1.Confirm which code you have. P0250 is circuit high and P0249 is circuit low, and they call for almost entirely different tests.
2.Record all stored codes. P0246 (the "A" solenoid high code) alongside this one points at a shared power feed, relay, or ground rather than at two failed solenoids.
3.Identify which physical solenoid your engine calls "B" from service data, since it determines both the test point and the labor.
4.Determine whether the solenoid is ground-side switched, which most are. If so, the control-wire voltage should drop when the module commands the solenoid on.
5.Watch control-wire voltage with a meter while commanding the solenoid on and off with a scan tool. Voltage that will not drop on command points at the ground path or the module driver, not at the solenoid.
6.Measure the solenoid's ground for low resistance under a small load. A continuity beep is not sufficient — corroded grounds pass continuity and still fail in service.
7.Disconnect the solenoid and check the control wire for voltage with the key on. Voltage present with the solenoid unplugged and the circuit not commanded confirms a short to voltage in the harness.
8.Inspect the "B" solenoid connector for corrosion, water intrusion, and any sign that adjacent circuits have shorted together through the connector body.
9.Follow the harness run looking for shiny or flattened spots where it has rubbed, pinch points under clamps, and melted or discoloured insulation near the turbo and exhaust manifold.
10.Wiggle-test the harness while watching control-wire voltage, since a short to voltage is frequently intermittent and position-dependent.
11.Measure the "B" solenoid's coil resistance and compare it against the healthy "A" solenoid on the same engine to rule out an internally shorted coil.
12.Confirm the correct part is fitted in the "B" position if the vehicle has a repair history there, since the two positions do not always use the same valve.
13.Suspect the module driver only after the ground, the control wire, the connector, and the solenoid coil have all been verified good.

Repair cost

$110 – $1,000

A ground repair is often the cheapest real fix on this code at $80-$220, since it may amount to cleaning and re-torquing a corroded connection. The solenoid runs $50-$220 in parts, with 0.3-2 hours of labor on the "B" position because it is frequently the buried one, putting a solenoid replacement between $110 and $500. Connector and terminal repairs commonly land at $120-$300. Tracing and repairing a short to voltage generally runs $180-$550 — the cost is in finding it, not in the wire, and heat-damaged sections near a turbo usually need replacing rather than splicing. Diagnosis commonly runs $110-$200. The upper end covers harness work on engines where reaching the second turbo means removing intake plumbing or other components first.

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DIY vs shop

This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.