P0016
- Powertrain
- Generic (SAE)
- Emissions
Get it looked at now
The most common mechanical cause, a chain that has jumped or is about to, can allow pistons and valves to meet on an interference engine, which is a several-thousand-dollar failure from a single further start. Even when the cause turns out to be a sensor, the possibility of a jumped chain is serious enough to change how the car should be driven until it is ruled out.
- Safe to drive
- Treat as serious. Keep driving to a minimum until the cause is identified - a chain can be a tooth off, or about to skip, with no noise and no symptoms at all. Any startup rattle, rough running or hard starting means stop and have it towed. On an interference engine the tow is far cheaper than the gamble.
Crankshaft Position - Camshaft Position Correlation (Bank 1 Sensor A)
The computer compared where the crankshaft is to where the camshaft is and found the two out of step with each other. That means either the mechanical timing has shifted, or one of the sensors reporting position is lying. Treat it as a serious code until proven otherwise.
The ECM knows crank position from a toothed reluctor wheel and cam position from a cam sensor reading a lobed target. It learns the expected angular offset between them. If the cam sensor edge arrives at a crank position outside the calibrated window, P0016 sets. That offset can move for mechanical reasons, a stretched chain, a worn or failed tensioner, a slipped or damaged reluctor, a phaser stuck off its home position, or for signal reasons, a failing sensor, wiring fault, or reference voltage problem.
How the car detected itOn most calibrations the ECM samples the crank angle at which each cam sensor edge occurs, averages it over several revolutions, and compares it to the stored expected value. Exceeding the tolerance window, which on many engines corresponds to roughly one chain tooth of movement, sets the code. Many vehicles run this test at startup and again during steady-state running, which is why the code often accompanies a long crank or a hard start.
A trouble code records what a control module measured. It does not identify which part failed. Test before replacing anything.
- Safe to drive
- Treat as serious. Keep driving to a minimum until the cause is identified - a chain can be a tooth off, or about to skip, with no noise and no symptoms at all. Any startup rattle, rough running or hard starting means stop and have it towed. On an interference engine the tow is far cheaper than the gamble.
- Urgency
- Get it looked at now
- Will it pass emissions
- No
- If ignored
- If a chain, guide or tensioner is the cause, continued driving lets the chain skip further. On an interference engine that means bent valves, damaged pistons and possibly a scrapped cylinder head, turning a 1200 dollar timing job into a 4000 dollar rebuild. If the cause is a phaser starving for oil, ignoring it also means ignoring an oil supply problem that reaches the bearings. Even in the benign sensor case the engine may stall without warning in traffic.
- 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 | Timing chain stretched | Very common | — |
| 2 | Chain tensioner worn or stuck | Common | — |
| 3 | Cam phaser internally failed | 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.
Any noise from the front or rear of the engine, especially a rattle in the first seconds after a cold start
A brief startup rattle that fades is the classic sound of a chain tensioner not holding pressure. Hearing it moves the diagnosis to mechanical immediately and argues against driving the car. Hearing nothing does not clear the chain - a tooth of movement is often completely silent.
Oil level, oil condition and the oil change history
Chain tensioners are hydraulic and chain wear accelerates dramatically on neglected oil. Sludge is both a cause and a symptom here.
The full code set, not just P0016
Companion codes matter. Cam or crank sensor circuit codes point toward electrical; P0011 or P0014 alongside it points toward the phaser; multiple correlation codes on different banks point toward the chain or a shared drive.
Recent repair history
If the engine was recently apart for a timing job, water pump, head gasket or cam sensor, an assembly error is far more likely than a random failure.
Cam and crank sensor connectors and harness routing
A loose connector, chafed wire or a harness resting against a hot or moving part produces an identical correlation error and costs nothing to inspect.
Read freeze frame and note whether the fault set at startup or under load
Tools Scan tool
A code that sets during cranking or the first seconds of run time leans toward a tensioner that bled down overnight. One that sets at steady cruise leans toward a sensor or a phaser holding an angle.
ExpectedA recorded set of conditions placing the fault either in the first seconds of run time or at steady operating conditions. Capture and write this down before clearing anything - it is the only record of the failure conditions and it directs every step that follows.
Inspect and electrically verify both position sensors
Tools Digital multimeter, scan tool
Check power, ground and signal at the cam and crank sensors, and look for damage, oil contamination on the sensor tip and metal debris stuck to the magnet. Wiggle-test the harness while monitoring the signal.
ExpectedStable reference voltage, clean grounds, no interruption during the wiggle test.
Capture cam and crank waveforms together on a scope
Tools Two-channel oscilloscope
This is the decisive electrical test. Overlay the crank signal and the cam signal and look at their relationship across several revolutions. A clean but shifted relationship indicates a real mechanical offset. Dropouts, noise, or an intermittent extra or missing pulse indicate a sensor or reluctor problem.
ExpectedBoth signals clean and repeatable, with a consistent phase relationship revolution to revolution.
Check the crank reluctor and cam target for damage
Tools Borescope, inspection light, service information
A cracked or slipped reluctor ring, or a target wheel that has spun on the cam, mimics a timing fault exactly. Look for a machined key or dowel that has sheared, and for debris in the sensor gap.
ExpectedA trigger wheel that is intact, correctly located on its key or dowel, and free of debris in the sensor gap. Cracking, movement on the shaft, or a sheared key is a confirmed cause and explains the correlation error without any chain wear.
Verify oil pressure and phaser behavior
Tools Mechanical oil pressure gauge, bidirectional scan tool
Measure oil pressure against specification and, with a bidirectional tool, check whether the phaser is sitting at its home position at idle. A phaser whose lock pin has failed will not park at home and will throw the correlation off without any chain wear at all.
ExpectedOil pressure meeting the manufacturer's specification, and the phaser parked at its home position at idle. A phaser that will not park home with pressure verified good points at a failed lock pin rather than the chain.
Physically verify mechanical timing
Tools Timing tools for the specific engine, torque wrench, service information
Bring the engine to the manufacturer's reference position and compare the actual cam and crank marks. On many engines this requires removing a cover or an access plug; on some it can be judged with a borescope. Do not rotate the engine backward and follow the make's procedure, because timing marks, tools and reference positions vary entirely by engine.
ExpectedCam and crank marks aligned exactly as the manufacturer's procedure shows at the reference position. An offset of a tooth or more is a confirmed mechanical fault, and on an interference engine the engine should not be run again until it is corrected.
Assess chain stretch and guide condition directly
Tools Service information, straight edge, magnet and inspection light
With the cover open, measure chain slack against specification and inspect guides and the tensioner for grooving, plastic debris in the pan, and a tensioner that will not hold extension. Plastic fragments in the oil pan confirm guide failure.
ExpectedChain slack within the published specification, guides unworn, and a tensioner that holds extension without bleeding down. Grooved guides, plastic fragments in the pan, or slack beyond specification confirms the chain assembly as the cause.
Confirm the repair with a relearn and a full drive cycle
Tools Scan tool supporting the relearn procedure
Many vehicles require a cam and crank variation relearn after sensor or timing work. Skipping it can leave the code returning on a correctly repaired engine.
ExpectedRelearn completes and the code does not return after a full drive cycle.
| Repair | Only after you confirm | Typical cost | Who |
|---|---|---|---|
| Replace the camshaft or crankshaft position sensor | Scope showing dropouts, noise or missing pulses from that sensor while mechanical timing verifies correct | $150–$480 | DIY |
| Repair sensor wiring or connector fault | Signal interruption on a wiggle test, or a failed voltage-drop test on power or ground | $100–$400 | DIY |
| Replace the timing chain, tensioner, guides and seals | Measured chain slack beyond specification, damaged guides, a tensioner that will not hold, or marks physically out of alignment | $900–$3,200 | Shop |
| Replace the camshaft phaser | Phaser failing to park at its home position at idle with good oil pressure, or a failed lock pin found on inspection | $800–$2,600 | Shop |
| Replace a damaged or slipped reluctor or cam target wheel | Cracked, loose or debris-fouled trigger wheel found on inspection, matching an irregular scope pattern | $300–$1,600 | Shop |
| Correct low oil pressure or remove sludge, including oil pump or pickup service | Measured oil pressure below specification, or a restricted pickup screen found on inspection | $600–$3,000 | Shop |
| Re-time the engine correctly after a previous repair error | Timing marks found out of alignment by a tooth with all components otherwise serviceable | $400–$1,800 | Shop |
US independent-shop ranges, parts plus labor. Timing chain work is dominated by labor and access. A single-chain inline four is at the low end; a transverse V6 or a V8 with multiple chains, phasers and a cover buried behind accessories runs to the high end and beyond. Get a written estimate that includes guides, tensioner and cover seals, not just the chain. Diagnosis on this code often runs 150 to 300 dollars because it justifies scope time, and that is money well spent given what the wrong guess costs.
- Replacing the camshaft position sensor because the code names it. The sensor is the messenger; scope it before condemning it.
- Treating a quiet, normal-running engine as evidence the chain is fine. A chain a tooth off, or a tensioner about to let it skip, is frequently silent and produces no driveability symptom at all.
- Continuing to drive an interference engine that rattles on startup, hoping it is only a sensor. That gamble costs valves.
- Doing a timing chain without the guides, tensioner and, where applicable, the phasers. The worn parts that stretched the chain will chew the new one.
- Forgetting the cam and crank variation relearn after replacing a sensor or reassembling timing, then chasing a code that is only a missing calibration.
- Blaming the chain on a well-maintained low-mileage engine before checking the reluctor wheel and connectors.
- Ignoring the oil supply. If sludge or low pressure let the tensioner collapse, replacing the chain alone repeats the failure.
- Camshaft Position Sensor
- Crankshaft Position Sensor
- Timing Chain
- Timing Chain Tensioner
- 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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