P0366 Code: Camshaft Position Sensor B Range/Performance (Bank 1)
Bank 1 exhaust cam signal is out of position: chain stretch, a sticky exhaust phaser or a slipped sprocket.
At a glance
Severity: Moderate
- Meaning
- Camshaft Position Sensor B Range/Performance (Bank 1)
- System
- Ignition & Misfire · Powertrain
- Safe to drive?
- With caution
- Typical repair cost
- $50–$3,000
- DIY difficulty
- Hard
P0366 means the bank 1 exhaust cam sensor (sensor B on most makes) is sending edges, but they arrive at the wrong crank angle or in the wrong number. The computer compares each exhaust cam edge with the crank tooth count and with where it has commanded the exhaust phaser to be; when the gap between expected and measured grows beyond a few degrees, it sets this code and usually parks exhaust cam timing. On a timing chain engine, a stretched chain shifts each camshaft by an amount that grows with how far along the chain's tight side its sprocket sits. That is why, on some engines, the exhaust cam shows chain wear first as P0366 while the intake cam still looks acceptable, and on others the reverse happens with P0341.
Can I keep driving? Usually drivable, but don't ignore it. If a stretched chain or loose sprocket is the cause, the timing can slip further and, on interference engines, damage valves. Avoid high rpm and get the timing checked soon.
How to read P0366
- P Powertrain
- 0 Generic (SAE)
- 3 Ignition / misfire
- 66 Specific fault
Symptoms
- Check-engine light, often together with an exhaust cam timing code
- Rough or lumpy idle, especially when warm
- Short rattle at cold start that fades after a few seconds
- Less low-end torque and slightly higher fuel use
- Code returns quickly after clearing, even with a new sensor
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- Timing chain stretch or worn guides and tensioner
- Exhaust cam phaser sticking, or its oil control valve or screen clogged
- Exhaust cam sprocket or phaser timed wrong, or slipped on a keyless camshaft after timing work
- Low oil level, old oil or incorrect viscosity
- Damaged or loose target wheel on the exhaust cam
- Sludge or metal on the sensor tip, or an erratic sensor
- Incorrect replacement sensor
Diagnosis step by step
Check the oil and service history
Top up and change the oil if it's low or overdue, using the specified viscosity. Ask whether timing work was done recently; a P0366 that appeared right after a belt or chain job is almost always a timing installation issue.
Tools: Flashlight
Compare intake and exhaust cam deviation
On a scan tool at warm idle, look at the actual angle or deviation for both camshafts. If both are shifted in the same direction, the chain has likely stretched. If only the exhaust cam is off while the intake is correct, suspect the exhaust phaser, its sprocket or its target wheel.
Tools: OBD-II scanner
Test the exhaust oil control valve
Measure the valve's coil resistance against the spec (often somewhere around 6 to 13 ohms). Then command the exhaust phaser with a bi-directional scan tool and watch whether the actual angle follows. A valve that clicks but produces no angle change often has a blocked screen or a stuck phaser.
Tools: Multimeter, OBD-II scanner
Inspect the sensor and target wheel
Remove the exhaust cam sensor, clean the tip and check for rub marks, which mean the target wheel is loose or wobbling. With the sensor out, turn the engine by hand and look at the wheel through the opening if the design allows.
Tools: Screwdriver, Flashlight
Lock the engine and check timing
If the data point to a mechanical offset, set the engine to its timing position with the manufacturer's locking tools or marks. On engines whose cam sprockets are not keyed to the shaft, a sprocket that has slipped will be obvious. Replace chain, guides and tensioner if stretch exceeds the limit, and torque sprocket bolts exactly to spec.
Tools: Torque wrench, Flashlight
Where the parts are
- 1Ignition coil
- 2Spark plug
- 3Fuel injector
- 4Camshaft sensor
- 5Crankshaft sensor
- 6Engine computer (ECM)
- 7Intake manifold
Repair options & costs
| Repair | DIY? | Estimated cost |
|---|---|---|
| Oil change with correct viscosity | Yes | $50–$120 |
| Replace exhaust oil control valve | Yes | $150–$450 |
| Replace exhaust cam phaser | No | $500–$1,400 |
| Re-time slipped exhaust cam sprocket | No | $350–$900 |
| Replace timing chain kit | No | $1,000–$3,000 |
Rough US estimates for parts and labor; shop rates vary by region. Not a quote.
Notes by brand
Field data
| Hyundai | 2 | Elantra, Kona |
|---|
Source: NHTSA Complaints API (US government open data), analyzed by DTC mention.
Emissions / smog test impact
Will fail
A stored P0366 with the check-engine light on fails a state OBD emissions test. If the root cause is mechanical, the code will return after clearing, so fix the timing issue before the retest.
Frequently asked questions
Why does a worn chain show up on the exhaust cam first?
A stretched chain moves each camshaft by an amount that depends on how many links sit between it and the crank on the chain's pulling side. On engines where the exhaust sprocket is further along that run, the exhaust cam drifts more and trips P0366 before anything else. On other layouts, the intake cam and P0341 go first.
What's the difference between P0365 and P0366?
P0365 is an electrical problem: the exhaust cam signal is missing or unusable. P0366 means the signal is fine electrically but arrives in the wrong place, which points to mechanical timing, the phaser, or the target wheel.
Can a timing job done elsewhere cause P0366?
Yes, and it's common. On engines with keyless cam sprockets, the exhaust cam can be locked a few degrees off, or the sprocket can slip if the bolt wasn't torqued correctly. The engine may run, but the computer sees the exhaust cam out of position.
Will clearing the code and driving fix it?
Only if the cause was temporary, such as a low oil level that has since been corrected. If the chain, phaser or sprocket is really out of position, the code will return within one or two drives.