Symptoms of a Bad Camshaft Position Sensor: What Reports Show

The camshaft position sensor tells the engine computer where the camshaft is, so the computer can time the spark and fuel. When it fails, the engine loses the thread — it stalls, or it cranks and will not start — often intermittently, which makes it maddening to catch. It is also rarely named by owners: of 165,897 complaints we pulled across model years 2010 to 2020, only 139 name a cam sensor, because drivers report the stall and the workshop names the part. That makes this a small set, treated as such: the symptom rates are directional, and the findings we lean on are the ratios against the large control.

The signature: a car that stalls

If a cam-sensor complaint has a defining symptom, it is stalling: it appears in 51.1% of them — half — against 25.4% of the control, twice as often. The mechanism is direct: without a reliable camshaft signal the computer cannot time combustion, so the engine simply quits, sometimes at idle, sometimes at speed. Loss of power and limp mode (18.7% against 10.5%) belong to the same story — a computer getting a bad or missing signal often pulls the engine back to protect it before it dies outright. A car that stalls and restarts, especially warm, with no obvious fuel or ignition cause, should put the cam and crank sensors near the top of the list.

The other classic: an intermittent no-start

The cam sensor’s second signature is a car that cranks but will not fire, in 10.8% of reports against 4.8% of the control. What makes it distinctive is the pattern: it is frequently intermittent and heat-related — the car starts fine cold, refuses when hot, then starts again once it cools, as a marginal sensor drops out at temperature. That “it wouldn’t start, waited, then it did” account is the cam sensor’s calling card, and it is why the fault so often survives a first trip to the shop where the car starts perfectly on the lift. Our guide to why a car won’t start covers the wider no-start tree.

Its twin: the crankshaft position sensor

The clearest thing in the data is not a symptom but a companion. A cam-sensor narrative names the crankshaft position sensor in 15.8% of cases against just 0.4% of the control — roughly forty times as often — because the two sensors do the same kind of job at different shafts, throw related codes, and are the classic pair a shop tests and often replaces together. A timing chain or belt appears in 9.4% against 1.7%, since a stretched chain throws the cam and crank out of sync and lights the same family of codes. The practical reading: a cam-sensor code and a crank-sensor code are close cousins, and diagnosing one means considering the other and the timing components that drive both.

Why the file is thin on the cam sensor

The 139 is worth being explicit about. The cam sensor is not a rare failure — it is a rarely-named one. An owner experiences a stall or a no-start and files a complaint about that; the camshaft position sensor is identified later, by a scan tool and a workshop. So the federal complaint file, which records owners’ own words, under-counts it exactly as it under-counts the mass air flow sensor and anything else found only after a diagnosis. That is the honest limit here, and the reason the strongest evidence on this page is the association with the crankshaft sensor rather than the raw symptom counts.

What to do when you suspect it

Start with the code. A cam-sensor fault typically stores a P0340 or P0341, and a crank-sensor fault a P0335 or P0336 — reading them beats guessing from an intermittent stall. Because the two sensors are cousins, a good diagnosis considers both, along with the wiring to them, which is a common real cause of an “intermittent sensor.” A cam sensor is an inexpensive part, but replacing it on a guess is how people end up having replaced the sensor, the crank sensor and the coil while the fault was a chafed wire. If a warm restart makes the fault vanish, that intermittency is itself the clue — and a reason to catch the code while it is stored.

On a used car you are about to buy

An intermittent stall or no-start is the easiest serious fault to miss on a test drive, because the car may behave perfectly for the twenty minutes you have it. Scan for stored and pending codes rather than trusting a car that started fine, and take any history of “it stalls sometimes” seriously. Checking the model and year in the complaint lookup and its open recalls is worth the minute, since stalling faults draw both complaints and campaigns.

Common questions

What are the symptoms of a bad camshaft position sensor?

In 139 owner reports, the signature is stalling — present in 51.1%, twice the control rate — because the sensor supplies the timing signal the engine needs to run. The other classic is an intermittent no-start (10.8%), often heat-related. A check-engine light is near-universal (59%). Its clearest fingerprint, though, is being named alongside the crankshaft position sensor about forty times as often as other engine complaints are.

Is it the camshaft or crankshaft position sensor?

They are cousins and hard to separate by feel — which is why cam-sensor complaints name the crank sensor forty times as often as the control does. Read the codes: a P0340/P0341 points at the cam sensor, a P0335/P0336 at the crank sensor. A good shop tests both and checks the wiring, because an intermittent “sensor” fault is often a chafed wire feeding one of them.

Can a bad cam sensor cause a car to stall?

Yes — stalling is its most common symptom, in 51.1% of these reports against 25.4% of other engine complaints. Without a reliable camshaft signal the computer can’t time combustion, so the engine quits, at idle or at speed, and often restarts. A car that stalls and restarts with no obvious fuel or ignition cause is a strong cam-or-crank-sensor candidate.

Why does my car start when cold but not when hot?

That heat-related, intermittent no-start is a classic cam or crank position sensor pattern: a marginal sensor works cold but drops out as it warms, so the car cranks without firing until it cools. It appears in the cam-sensor reports at more than twice the control rate. Catch the stored code while the fault is present, and have the sensor and its wiring tested rather than replaced on a guess.