P004A

Turbocharger/Supercharger Boost Control B Circuit/Open

Q: Is it safe to drive with P004A?

Briefly and gently. The engine will limit boost, so it's down on power — get the boost-control circuit repaired before driving normally.

Q: Can I just clear P004A?

It comes straight back while the circuit is open. The broken wire, connector, or solenoid has to be fixed first.

Turbocharger / boost control Generic OBD-II High

What it means

P004A means the ECM has detected an open (broken) electrical connection in the "B" turbocharger/supercharger boost-control circuit. With the circuit open the ECM can't command the boost-control solenoid, so it defaults to minimum boost or limp mode to protect the engine. The usual causes are a broken wire, a bad connector, or a failed solenoid coil — so you'll notice reduced power rather than a no-start.

High

Can I keep driving? Reduced — with the boost-control circuit open the ECM usually forces minimum boost or limp mode; you can limp home but power will be well down.

Real-world scan data

Seen in

scans in the past year

Found in

<0.1%

of scans

<0.1%

of scans that found faults

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

Common symptoms

What you'll notice

Check-engine light on
Noticeable loss of power / limp mode
Little or no boost from the turbo/supercharger
No boost response when you press the pedal

Common causes

Most likely first

Open (broken) wire in the 'B' boost-control circuitLikely
Disconnected, corroded, or damaged boost-control solenoid connectorCommon
Failed boost-control solenoid with an open coil windingCommon
Chafed or cut harness between the solenoid and the ECMLess often
Faulty ECM boost-control driver (rare — rule out wiring first)Less often

How to diagnose & fix

Work through it in order

Read freeze-frame data to confirm when the open is detected (usually as soon as boost is commanded).
Inspect the boost-control solenoid connector for backed-out pins, corrosion, or a loose fit.
Measure the solenoid coil resistance — an open (infinite) reading means the solenoid is bad.
Check continuity of the control and feed wires back to the ECM; repair any open or chafed section.
If wiring and solenoid are good, suspect the ECM driver; clear the code and re-test after any repair.

FAQ

Quick answers

Is it safe to drive with P004A?+

Briefly and gently. The engine will limit boost, so it's down on power — get the boost-control circuit repaired before driving normally.

Can I just clear P004A?+

It comes straight back while the circuit is open. The broken wire, connector, or solenoid has to be fixed first.

Read & clear P004A yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX