Drivable short-term; check oil and fix soon. P0027 means the exhaust camshaft's oil control valve on bank 1 is failing a range/performance check: the solenoid is electrically fine, but the exhaust cam is not reaching or holding the camshaft phasing the engine computer commanded. Because the phaser is oil-driven, the trouble is usually low or dirty oil, a clogged control-valve screen, or a worn phaser rather than the electrical circuit.
What P0027 means
Modern engines vary exhaust valve timing with a camshaft phaser mounted on the end of the exhaust cam. The phaser is a hydraulic vane actuator: pressurized engine oil, metered by an oil control valve (OCV) - also called the exhaust valve control or variable valve timing solenoid - is routed into advance or retard chambers to rotate the cam relative to the crankshaft. The engine computer drives that OCV with a variable duty-cycle (PWM) signal, then watches the exhaust camshaft position sensor to confirm the cam actually moved to the commanded angle. P0027 is the range/performance outcome of that closed-loop check on bank 1: the OCV circuit is electrically intact, but the measured cam phase does not track the commanded phase within the calibrated tolerance and time window, or the cam sticks away from its commanded position. Because the phaser is oil-actuated, the root cause is usually hydraulic rather than electrical - low or degraded oil, wrong viscosity, a clogged OCV filter screen, a valve stuck by varnish, worn phaser vanes, or restricted oil galleries all keep the cam from reaching its target even when the solenoid is being commanded correctly. The computer flags that commanded-versus-actual discrepancy, lights the check-engine lamp, and may limit how far it trusts the exhaust cam.
Symptoms
- Rough, unstable, or fluctuating idle, sometimes with a slight surge
- Reduced power and sluggish, flat acceleration under load
- Poorer fuel economy as timing sits away from its optimal point
- A brief rattle or tick from the front of the engine, most noticeable on cold start-up
- Check-engine light on, occasionally with hard starting or a light hesitation
Common causes
- Low, dirty, sludged, or wrong-viscosity engine oil starving or slowing the phaser
- A clogged oil control valve filter screen or a valve spool stuck by varnish so oil cannot be metered correctly
- A worn exhaust camshaft phaser - loose vanes or a failed locking pin - that cannot hold the commanded angle
- A failing or sticking oil control (VVT) solenoid that responds electrically but meters oil poorly
- Damaged wiring or a poor connector to the solenoid, or a restriction in the oil galleries feeding the phaser
Severity & driving advice
Severity: Moderate — Usually drivable, but incorrect exhaust cam timing hurts power and economy and, if oil-related, can lead to phaser and timing-chain wear.
Can I drive? Drivable short-term; check oil and fix soon.
Diagnostic approach
- Confirm the code and check oil first — Read P0027 with its freeze-frame data and note any companion camshaft-position or correlation codes. Recognize this is a range/performance fault, not a simple open or short, so start with the hydraulics: verify the oil level, condition, and correct viscosity. Old, sludged, or overdue oil is the single most common trigger and should be corrected before deeper testing.
- Compare commanded versus actual cam angle on a scan tool — With live data, watch the desired and actual exhaust camshaft angle in degrees. A healthy phaser follows the command within a few degrees and settles quickly. Use bidirectional control to sweep the OCV and confirm the exhaust cam moves and then holds; if the computer commands a change but the actual angle barely responds, the fault is hydraulic or mechanical rather than in the sensor.
- Test the oil control valve and its filter screen — With the solenoid connector off, measure OCV winding resistance - typically in the rough range of 6.5 to 8 ohms at about 20 C (68 F), confirmed against the specific OEM value - and reject an open or shorted reading. Remove the valve and inspect the fine filter screen and spool for varnish or debris; a partially blocked screen lets the solenoid pass its electrical test while still failing to meter oil, which is exactly what a range/performance code describes.
- Verify oil pressure and phaser mechanical health — Confirm engine oil pressure meets specification, since a weak pump or worn bearings can leave the phaser under-pressurized only under load. If pressure and the OCV are good but the cam still will not track its command, suspect a worn phaser or a stretched timing chain; check camshaft-to-crankshaft correlation and inspect the phaser and chain guides.
- Inspect wiring, then clear and road-test — Check the solenoid connector, harness, and ground for corrosion, chafing, or spread terminals that could intermittently disturb control. After any repair - oil service, OCV, phaser, or wiring - clear the code and drive through a full range of load and rpm so the monitor reruns, then confirm P0027 does not return and commanded and actual cam angles now match.
Make & model notes
Toyota: Toyota's dual VVT-i engines phase the exhaust cam with an oil-fed actuator and a camshaft timing oil control valve. Because Toyota's phaser control is highly oil-sensitive, technicians check oil level, condition, and the OCV filter screen first; a sludged screen or overdue oil commonly keeps the exhaust cam from reaching its commanded angle even when the solenoid passes its resistance test. Verify commanded versus actual cam angle in the data list before condemning the phaser.
Jeep: Jeep and Chrysler engines such as the Pentastar V6 use oil-pressure-actuated cam phasers governed by an oil control valve; poor oil condition and clogged control-valve screens are a well-known cause of cam-phasing performance faults. Inspect the OCV screen and confirm oil pressure and quality before replacing the phaser, since a worn phaser and a starved one produce the same commanded-versus-actual mismatch.
Hyundai: Hyundai and Kia continuously variable valve timing (CVVT) systems set exhaust valve control range/performance codes when the OCV meters oil poorly or the phaser sticks. These engines are sensitive to oil viscosity and level, so a correct oil-and-filter service with the specified grade often clears the fault; if it persists, test the OCV and inspect the phaser screen and cam timing.
FAQ
What is the difference between P0027 and an exhaust valve control circuit code?
P0027 is a range/performance code, which means the oil control valve is electrically working but the exhaust cam is not reaching or holding the timing the computer commanded. Pure circuit codes instead flag an open, short, or wiring problem in the solenoid's electrical path. In practice, P0027 shifts attention away from the wiring and toward oil condition, the control valve's oil metering, and the phaser itself.
Can low or dirty oil really cause P0027?
Yes - it is the most common cause. The cam phaser is moved entirely by pressurized engine oil, so low level, the wrong viscosity, or sludged and overdue oil can stop the cam from reaching its commanded angle even with a healthy solenoid. Many P0027 cases clear after a correct oil-and-filter change and cleaning or replacing the oil control valve's filter screen, so that is the sensible first step.
Is it safe to drive with P0027?
It is usually drivable in the short term, since the engine still runs, but you will likely notice reduced power, a rougher idle, and worse fuel economy while the exhaust timing sits away from its ideal point. The bigger concern is that an oil-related fault can accelerate wear on the phaser and timing chain. Check and correct the oil promptly and have the cause diagnosed rather than ignoring it.
Do I need to replace the camshaft phaser to fix P0027?
Not usually. Start with the cheaper, more common causes - engine oil, the oil control valve, and its filter screen - because a starved or poorly metered phaser behaves the same as a worn one. Only after oil, oil pressure, and the control valve all check good, and the cam still will not track its commanded angle, should the phaser or timing chain be replaced.