What it means
The ECU detects that the exhaust camshaft oil control valve on bank 1 does not respond to commanded duty cycle within expected limits. Camshaft phase deviates from target during phaser actuation tests.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The Bank 1 exhaust valve control solenoid directs oil to the exhaust cam phaser so the module can adjust exhaust valve timing. P0027 sets when the Bank 1 exhaust cam’s response to the commanded adjustment falls outside the expected range or performance.
Common causes
Most likely first.
- Oil control valve clogged with sludge
- Low oil pressure or wrong oil viscosity
- Camshaft phaser worn
Symptoms
- Check engine light on
- Rough idle or engine hesitation
- Reduced power or acceleration
- Poor fuel economy
How to diagnose it
- Record freeze-frame data and compare commanded and actual Bank 1 exhaust cam timing in live data to establish when the response deviates.
- Check oil level, condition, and viscosity against the specified requirements before suspecting the actuator, since oil supply affects exhaust phaser movement.
- Inspect the Bank 1 exhaust oil control solenoid, connector, and nearby wiring for sludge, damage, corrosion, or poor connections.
- Test the solenoid and its circuit and verify its response to commands using the wiring diagram and manufacturer’s specification.
- If those checks are satisfactory, investigate restricted exhaust cam oil passages or a worn or sticking Bank 1 exhaust phaser.
Common fixes
- Top up or replace incorrect or degraded oil and filter with the specified type.
- Clean the Bank 1 exhaust oil control solenoid and oil passages where the manufacturer’s procedure allows.
- Repair loose, corroded, or damaged wiring and connector terminals at the Bank 1 exhaust solenoid.
- Replace a solenoid or exhaust cam phaser confirmed to be sticking or worn.
Can I keep driving?
A short, gentle trip may be possible if the light is steady and the engine remains smooth, but avoid hard acceleration because power and fuel economy may worsen. Stop if the engine stalls, becomes very rough, or develops abnormal mechanical noise.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.