P0335

00:00What this code means

Code P0335. Crankshaft Position Sensor A Circuit Malfunction.

In plain English: the engine computer lost the crankshaft speed-and-position signal it needs to control ignition and injection; P0335 identifies the signal circuit, not automatically a failed sensor.

A missing crank signal can stall the engine or prevent the next restart. If the engine has stalled, cranks without starting, or the tachometer and scan-tool RPM drop out, arrange a tow. Even if it currently runs normally, an intermittent P0335 should be diagnosed before routine driving.

00:40How the test actually works

Here's what your engine computer is actually measuring.

A toothed reluctor rotates with the crankshaft. As each tooth passes the crankshaft position sensor, the sensor creates a voltage or digital pulse. The engine computer counts those pulses to calculate cranking and running speed, recognize crank position, and schedule spark and fuel injection at the correct time.

P0335 sets when the expected primary crankshaft signal is absent or electrically invalid while the computer believes the engine is cranking or running. Depending on the vehicle, the monitor can detect no pulses, an open circuit, a short to ground or voltage, or a signal that never switches. The code covers the entire circuit and cannot convict the sensor by itself.

So the code is not a part failure report. It's a performance measurement that came back under spec.

01:35Symptoms

What you'll usually notice, beyond the light itself.

Engine cranks but will not start. Without crank position, many controllers will not command normal spark or injector operation.

Sudden stall followed by a difficult or impossible restart. Heat can open an internally failing sensor or connection and let it work again after cooling.

Tachometer or scan-tool RPM remains at zero while cranking. That is a strong direction toward the crank signal, but a scope test is the proof.

Intermittent hesitation, cut-out or extended cranking. A loose terminal, damaged wire or marginal air gap may lose only an occasional pulse.

Check-engine light with P0336 or cam/crank correlation codes. Companion codes help separate a dead circuit from an incorrect or out-of-sync pattern.

02:32Most likely causes, ranked

Now the part you came for: what actually causes this, ranked by how often it turns out to be the culprit.

30 percent of the time, it's this: Failed crankshaft position sensor. Internal windings or electronics can fail permanently or open only when hot. Test the signal before replacing it.

25 percent of the time, it's this: Chafed wiring or a loose, oil-contaminated connector. The circuit lives near heat, vibration and moving engine parts; inspect the entire routed harness.

14 percent of the time, it's this: Missing sensor power, ground or circuit bias. Powered Hall-effect sensors need a clean supply and ground, while two-wire sensors require their own factory test method.

13 percent of the time, it's this: Damaged reluctor wheel, wrong air gap or loose sensor mounting. A good sensor cannot create the correct pattern if teeth are damaged or it sits too far from the target.

10 percent of the time, it's this: Low cranking voltage, slow starter speed or electrical noise. Weak voltage can reduce signal quality and can also make a no-start look like a sensor failure.

8 percent of the time, it's this: Control-module calibration or PCM input fault. Check application-specific service information only after the signal has been verified at the controller.

Notice that the most expensive repair is not the most likely one. That matters, because the cheap checks come first.

04:07The measurement that decides it

This is the single measurement that tells you whether you need the expensive part or the cheap one.

Connect the scan tool, keep the battery supported, and graph engine speed while cranking for several seconds. Confirm that the starter is actually turning the engine at a normal, even speed.

A known-good signal rises promptly to a steady cranking speed. That proves the computer is receiving enough crank information to calculate RPM at this moment, although an intermittent dropout may still need heat and harness testing.

A flat zero-RPM trace while the crankshaft is physically turning points toward a missing crank signal, its power or ground, the wiring, or the reluctor and air gap. Do not order a sensor from this clue alone.

Scan RPM is the fast screening test; a waveform measured at the sensor and then at the computer is the decisive test. If the waveform leaves the sensor but never reaches the PCM, the sensor is not the failed part.

05:08Diagnostic order

So here is the order to actually test this, cheapest and most likely first.

Step 1. Does the engine crank at normal speed with stable battery voltage? Start with the physical crank and electrical supply. A weak battery, dragging starter or damaged engine ground can lower signal amplitude and prevent a valid test. Use the vehicle's cranking-voltage and speed specifications.

Step 2. Does the scan tool show steady engine RPM while the engine is cranking? Graph RPM rather than watching one slowly updating number. A stable value means the PCM sees a crank signal now. Zero or repeated dropouts tell you to move from code reading to circuit measurement.

Step 3. Do required power, ground and circuit-bias checks match factory specification? Identify whether the vehicle uses a powered three-wire Hall sensor or a two-wire variable-reluctance sensor before testing. Never apply a generic voltage rule to the wrong sensor design.

Step 4. Is the correct CKP waveform present directly at the sensor while cranking? Use the specified meter or oscilloscope connection and compare amplitude, switching and tooth pattern with service information. Back-probe safely so the test does not spread or damage terminals.

Step 5. Are sensor mounting, air gap and reluctor teeth mechanically correct? Inspect for a loose sensor, debris on a magnetic tip, impact damage and a shifted or broken tone wheel. Some reluctors require a borescope or substantial disassembly to inspect.

Follow the signal from the rotating crankshaft to the computer. The point where it disappears identifies the branch to repair.

07:03Repair costs

What this costs to put right, in US dollars, parts and labor.

Connector or accessible wiring repair: 10 to 250 dollars in parts, plus about 1.5 hours of labor. Cost rises when the damaged section is buried behind covers or the transmission.

Crankshaft position sensor: 25 to 250 dollars in parts, plus about 1.0 hours of labor. Access ranges from one exposed bolt to removal of other components.

Battery, cable or starter correction: 20 to 500 dollars in parts, plus about 1.0 hours of labor. Only belongs here when cranking voltage or speed fails its test.

Reluctor wheel, air-gap or mounting repair: 50 to 600 dollars in parts, plus about 5.0 hours of labor. Some tone wheels are internal and require transmission or engine disassembly.

PCM calibration, input repair or module: 0 to 1500 dollars in parts, plus about 1.5 hours of labor. The rare final branch after a correct waveform has been proven at the PCM pins.

P0335 may be an inexpensive terminal repair or an internal reluctor job. The waveform path prevents a good sensor from being replaced when the signal is lost in the harness.

08:27Recap and related codes

Quick recap. P0335 means the computer lost the primary crankshaft position signal; it does not automatically mean the sensor failed. Confirm cranking voltage and speed, graph scan-tool RPM, identify the sensor type, test its supplies and waveform, then follow that waveform to the PCM before buying parts.

If your scan tool showed a related code alongside this one, check those too: P0336, P0339, P0340, P0341.

Codes are on screen and linked below.