P0012
- Powertrain
- Generic (SAE)
- Emissions
Diagnose soon
Cam timing stuck retarded costs power and fuel economy and will fail emissions, but the engine still runs and is not destroying itself in the short term. It escalates if the underlying cause is low oil pressure or oil starvation, because the same oil that moves the phaser lubricates the bearings.
- Safe to drive
- Usually drivable short term with reduced power. If oil pressure is low, oil level is down, or the engine rattles, stop driving.
"A" Camshaft Position - Timing Over-Retarded (Bank 1)
The computer commanded the bank 1 intake camshaft to shift its timing and the camshaft stayed too far retarded. It is a detection that the cam did not go where it was told, not proof that any single part has failed.
Variable valve timing phasers are hydraulic actuators driven by engine oil, metered by an oil control valve that the module pulse-width modulates. The module derives actual cam phase from the camshaft position sensor relative to the crankshaft signal and compares it against the commanded target. P0012 sets when actual phase remains retarded of the target by more than a calibrated amount for a calibrated time. The letter A refers to the intake camshaft on most dual-overhead-cam engines, or to the single camshaft on single-cam and pushrod designs.
How the car detected itThe module runs this test only when its enabling conditions are met, which almost always includes oil at operating temperature and engine speed and load inside a defined band, because cold thick oil cannot move a phaser quickly. It commands a phase change, waits, and measures the resulting position error. Persistent error in the retard direction sets the code. Because the whole system is oil-powered, oil condition and pressure influence the result as directly as any electrical part does.
A trouble code records what a control module measured. It does not identify which part failed. Test before replacing anything.
- Safe to drive
- Usually drivable short term with reduced power. If oil pressure is low, oil level is down, or the engine rattles, stop driving.
- Urgency
- Diagnose soon
- Will it pass emissions
- No
- If ignored
- Continued driving with reduced power and higher fuel consumption, and a failed emissions test. If the cause is degraded oil or clogged passages, the sludge that blocks the phaser feed is also restricting the timing chain tensioner and the bearings, which turns a solenoid job into a chain or engine job over time.
- Check engine light
- Solid
- Clearing the light
- A completed drive cycle is normally required before the monitor re-runs and the light can clear.
- Power loss especially in mid-rpm range
- Possible rough idle or stalling
- Increased fuel consumption
Many vehicles show no symptom at all beyond the warning light. The absence of a symptom does not mean the fault is not real.
These are the causes this code can have. For the order to work through them in, see what to check first.
| # | Cause | How often | Component |
|---|---|---|---|
| 1 | Oil control valve stuck (retard position) | Very common | — |
| 2 | Cam phaser internally worn | Common | — |
Ordering reflects how often each cause is responsible in general, not a probability for your vehicle. Confirm by testing.
In order. Each of these is cheaper or faster than what follows it, and each one can make the rest unnecessary.
Engine oil level, condition, and viscosity
The phaser is powered by oil pressure through very small passages. Low oil, overdue oil, or the wrong viscosity is a common and inexpensive cause of this code, and it must be ruled out before any part is bought because it costs less than anything you could buy.
Whether a circuit code such as P0010 is also stored
A circuit code means the solenoid or its wiring is electrically faulty, which changes the diagnosis completely. Fix the electrical fault first and retest.
Whether a crank-to-cam correlation code such as P0016 is stored alongside it
A correlation code points at mechanical timing, chain stretch, or a slipped sprocket rather than the phaser control system. That is a much bigger repair and you need to know before ordering parts.
Commanded versus actual cam angle on live data
This shows in seconds whether the phaser responds at all, responds sluggishly, or is completely stuck. It costs nothing and directs everything that follows.
The oil control valve connector and harness
These solenoids sit in oil and their connectors frequently fill with oil that wicks up the wiring, causing intermittent control. It is a visual check that takes minutes.
Verify oil level, condition, and the correct viscosity for the engine
Tools Basic hand tools, owner manual or service data
Check level on level ground with the engine off and settled. Look for sludge on the filler cap and dipstick. Confirm the viscosity in the engine matches what the manufacturer specifies, which varies by engine and cannot be assumed from what the last shop poured in.
ExpectedOil at full, clean, correct specified viscosity, within its service interval
Record freeze frame and all stored codes
Tools Scan tool
Note coolant temperature, rpm, load, and run time at the moment the code set. Codes that set at cold start behave differently from codes that set at cruise, and companion codes reshape the whole diagnosis.
ExpectedA recorded snapshot of the conditions at the fault and a full companion code list, captured before anything is cleared
Graph commanded versus actual cam position at idle and under load
Tools Scan tool with graphing
With the engine fully warm, watch the two values together. A healthy system tracks the command closely with only a small lag. A trace where actual stays flat at the fully retarded end while commanded moves is the fault the code describes.
ExpectedActual cam angle follows commanded angle within a few degrees
Command the oil control valve with the scan tool and watch the response
Tools Scan tool with bidirectional control
Use bidirectional control to sweep the solenoid duty cycle and observe whether the cam angle moves at all. No movement with a good electrical circuit points at the valve, the oil feed, or the phaser. Partial or sluggish movement points at oil supply or a worn phaser.
ExpectedCam angle moves smoothly and repeatably as the solenoid is commanded
Test the solenoid circuit electrically
Tools Multimeter, factory wiring diagram
Check for a good power feed and a working module driver, and measure the solenoid winding resistance with the connector unplugged. The correct resistance value varies by engine and must come from service data, though comparing against the same solenoid on the other bank is a useful sanity check when the engine has one.
ExpectedA stable resistance reading matching the service-data figure, or closely matching the same solenoid on the other bank. An open or near-zero reading condemns the winding; anything between needs the service-data number to judge.
Remove the oil control valve and inspect it
Tools Hand tools, fused jumper leads, clean solvent
Check the inlet screen for sludge, varnish, or metal debris. Confirm the spool slides freely by hand and returns under spring force. Energize it off the vehicle with a fused supply and watch the spool move fully. A screen packed with sludge tells you the oil, not the valve, is the underlying story.
ExpectedClean screen, free-moving spool, full travel when energized
Measure actual engine oil pressure hot
Tools Mechanical oil pressure gauge and adapter
Do not rely on the dashboard light or gauge. Fit a mechanical gauge and measure at idle and at raised rpm with the oil at operating temperature. Both the port location and the specification vary by engine, so use service data. Low pressure explains a phaser that will not move and demands its own diagnosis.
ExpectedMeasured pressure meeting the engine's specified figure at both idle and raised rpm, hot
Clear the code and confirm with a drive cycle
Tools Scan tool with data logging
Verify the cam angle now tracks the command through a full warm-up and a range of loads, and that the code does not return after the monitor has run. Do not judge the repair on a clean dash alone.
ExpectedCam angle tracks command, no codes return, monitor completes
| Repair | Only after you confirm | Typical cost | Who |
|---|---|---|---|
| Oil and filter change with the correct specified viscosity | Oil found low, degraded, sludged, overdue, or the wrong viscosity, with the cam responding correctly after the change | $60–$180 | DIY |
| Replace or clean the bank 1 intake oil control valve | Solenoid screen blocked, spool stuck, or no spool movement when energized on the bench, with a good electrical circuit | $150–$500 | DIY |
| Repair the solenoid wiring or an oil-contaminated connector | Circuit testing finds an open, a short, high resistance, or oil wicked into the connector body | $120–$450 | DIY |
| Engine cleaning service and correction of the cause of sludge | Heavy varnish or sludge found in the valve screen and on internal surfaces, with oil pressure still adequate | $200–$700 | DIY |
| Replace the bank 1 intake camshaft phaser | Verified good oil pressure and a proven-good solenoid, with the cam still failing to reach commanded position | $900–$2,500 | Shop |
| Diagnose and repair low oil pressure | Mechanical gauge reading below the engine's specification at operating temperature | $400–$3,500 | Shop |
Solenoid cost depends heavily on access. Some sit exposed on the front of the head; others require intake or timing cover removal. Phaser jobs usually mean opening the timing cover, so a shop will often replace chain, guides, and tensioner at the same time because the labor is already spent. Ranges are US independent-shop, parts plus labor.
- Buying a phaser or a chain kit before checking the oil. Old, low, or wrong-viscosity oil causes this code often enough that it should always be ruled out first.
- Replacing the oil control valve without inspecting its screen, which hides the sludge problem that will kill the new valve too.
- Confusing P0012 with P0011. Both are the same actuator on the same bank, but they describe opposite directions of failure and lead to different tests.
- Ignoring a simultaneous crank-to-cam correlation code, which points at the timing chain and makes phaser parts the wrong purchase entirely.
- Assuming bank 1 is the side nearest the front of the car. Bank 1 contains cylinder 1, and its physical location varies by engine layout.
- Testing at idle only. Some phaser faults appear only under load and heat, so a static test can pass a failing system.
- Camshaft Position Actuator
- Oil Control Valve
- Cam Phaser
- Definition
- Generic code set (SAE J2012 / ISO 15031-6) via the OBDexopen database, dedicated to the public domain under CC0-1.0.
- Diagnostic guidance
- Written and reviewed in-house. See our editorial policy.
- Review status
- Reviewed
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