P0084 fault code: Exhaust Valve Control Solenoid Circuit

P0084 means “Exhaust Valve Control Solenoid Circuit” — a fuel and air metering fault in the powertrain.

Can I DIY?

Professional-only boundary. Do not remove a second exhaust cam solenoid; take the scan to a garage.

Do not DIYReviewed page boundary
ToolsSpecialist equipment

This is the conservative boundary from the reviewed code record. This page has no frozen site-wide safety grade, so it does not publish a repair route.

What to tell the garage about P0084

Do not drive. A further exhaust-valve control solenoid circuit is faulty. On engines with two exhaust actuators, that second circuit can freeze exhaust timing on one cam while the first exhaust solenoid still works.

Take these reviewed, code-specific details with you. They help the garage confirm the fault without turning this page into a repair procedure.

  • Exhaust Valve Control Solenoid Circuit: Registration number
  • Exhaust Valve Control Solenoid Circuit: Exact code P0084 and any companion codes
  • Exhaust Valve Control Solenoid Circuit: Whether the engine management light is steady or flashing
  • Exhaust Valve Control Solenoid Circuit: Whether P0078 was stored with P0084
P00xxFuel and air metering
MOT fail riskif the warning light stays on

What does P0084 mean?

P0084 is a generic (SAE standard) powertrain code reported by your car’s engine control unit. It sits in the P00xx block, which covers fuel and air metering. The stored description is “Exhaust Valve Control Solenoid Circuit”. The code itself tells you which circuit or system tripped the fault — not always the exact part that failed.

Will P0084 fail an MOT?

A lit engine management light is a Major MOT defect. A second exhaust-valve solenoid circuit is not a MOT named heading.

Before booking your test, check what usually fails on your car: see our MOT pass rates by make and model, built from 33.1 million DVSA tests.

Related guides

Car diagnostic test cost: compare the scopeUK booking marketplaces currently publish diagnostic averages of about £52–£65. Engine management light on: steady or flashing?A steady engine management light means the computer has stored a fault. Drive with caution and get the code read. A flashing light is different — stop when it is safe.
P0001Fuel Volume Regulator Control Circuit/Open P0002Fuel Volume Regulator Control Circuit Range/Performance P0003Fuel Volume Regulator Control Circuit Low P0004Fuel Volume Regulator Control Circuit High P0005Fuel Shutoff Valve 'A' Control Circuit/Open P0006Fuel Shutoff Valve 'A' Control Circuit Low P0007Fuel Shutoff Valve 'A' Control Circuit High P0008Engine Position System Performance

P0084 — quick answers

Is it safe to drive with P0084?

Do not drive. P0084 has no verified driving guidance. Do not drive until checked. A second exhaust-cam solenoid circuit is not a milder copy of P0078.

Will P0084 fail my MOT?

A lit engine management light is a Major MOT defect. A second exhaust-valve solenoid circuit is not a MOT named heading.

Fault-code identifiers are standard diagnostic facts. Their explanations and diagnostic guidance on this site are original editorial summaries, not reproduced SAE wording. MOT defect rules reflect the DVSA MOT inspection manual (2026). This page is general guidance for UK drivers, not a substitute for a professional diagnosis.