OBD-II trouble code
P0337: Crankshaft Position Sensor "A" Circuit Low
SAE J2012: Crankshaft Position Sensor "A" Circuit Low. The signal is below the expected range. Test the connector, the wiring, and the sensor before any deeper engine work. A crank-signal fault can cause a no-start or a stall.
Quick facts
- System
- Powertrain
- Category
- Sensors / Timing
- Severity
- High severity
- Drivable
- No — stop driving until repaired
- Repair cost range
- $200 – $400 (crankshaft position sensor replacement)
- DIY difficulty
- Intermediate DIY
Browse every code in P0300–P0394, or start from the full code library.
What does P0337 mean?
P0337 is the 'circuit low input' member of the crankshaft position sensor 'A' family. The CKP sensor reads a toothed reluctor wheel on the crankshaft and reports engine position and speed — the master reference the PCM uses for spark timing, injector timing, and misfire detection. P0337 sets when the voltage on that circuit stays below the expected range: the signal is too low, too weak, or pulled down. That's an electrical complaint about signal level, in contrast to P0336 (signal present but implausible), P0335 (general circuit fault), and P0338 (signal too high).
Test the circuit and the sensor seating before the reluctor wheel. A short to ground, an open, a corroded connector, a failed sensor, and — on a three-wire sensor — a lost supply or ground can each hold the signal low. The chart says which. A sensor that is not fully seated, a doubled O-ring, a missing spacer, debris under the flange, or an aftermarket body of a different length changes the gap. Where the service information gives no air-gap adjustment, seating is the check. Do not invent a clearance. Because the level is wrong rather than the pattern, circuit testing — shorts, opens, supply and ground — is the productive path.
Before testing the sensor itself, establish which of the two kinds you have, because the right test is different for each and the wrong one produces a confident wrong answer. A two-wire sensor is a variable-reluctance magnetic pickup: it generates its own AC signal, with an amplitude that climbs as the engine turns faster. A three-wire sensor is a Hall-effect device fed a supply and a ground, and it switches a clean square wave between its rails. The two-wire type has a winding you can measure; the three-wire type does not, and its output is a digital pattern rather than a level.
The practical impact is significant: with the crank reference too low to use, the engine often won't start, or starts and stalls, runs roughly, or cuts out unpredictably. The tachometer may read zero or erratically during cranking. This is not a code to drive on casually — the engine can quit without warning and may strand you. Diagnosis starts at the sensor connector: verify supply and ground where applicable, check the signal wire for a short to ground or an open, inspect for corrosion, and confirm the sensor's output level against spec before replacing it.
Common causes
- Short to ground in the CKP signal wire pulling the circuit low
- Open circuit or high resistance collapsing the signal level
- Corroded or loose connector at the sensor
- Failed CKP sensor unable to drive the circuit to normal level
- Loss of supply voltage or bad ground on a powered (three-wire) sensor
- Sensor not fully seated — debris, a doubled-up O-ring, a missing spacer, or an aftermarket sensor of slightly different body length
- Damaged wiring shared with or routed near other circuits
Symptoms
- Check engine light with P0337 stored
- No-start or hard-start condition
- Engine that starts then stalls
- Rough running or unexpected stalling while driving
- Tachometer reading zero or erratically during cranking
- Intermittent loss of spark or fuel
Diagnostic steps
- 1.Inspect the CKP sensor connector first for corrosion, looseness, and backed-out pins — a frequent and quick-to-find cause.
- 2.On a powered sensor, verify supply voltage and ground at the connector before testing the signal.
- 3.Check the signal wire for a short to ground and for opens or high resistance back to the PCM.
- 4.Test the sensor according to its type. On a two-wire magnetic pickup, unplug it and measure the winding against the resistance figure in the service data — an open or a badly out-of-range winding condemns it outright — then scope the output while cranking and judge the waveform's shape and consistency rather than one voltage, because its amplitude legitimately rises and falls with cranking speed. On a three-wire Hall sensor, confirm supply and ground first, then scope for a square wave that swings fully between its rails.
- 5.Be wary of a multimeter here. It cannot confirm a crank signal is 'in spec': on a two-wire sensor it averages an AC pulse train whose level varies with cranking speed, and on a Hall sensor it reports a figure part-way between the two rails because the output is switching. It is useful for proving that something rather than nothing is being produced, and for supply, ground and continuity — the waveform decision belongs to a scope.
- 6.Confirm the sensor is properly seated and its mounting bolt torqued, with the correct single O-ring or spacer, since anything holding the tip away from the teeth weakens the signal.
- 7.Replace the sensor only after wiring, connector, supply, and ground all check out.
Repair cost
$200 – $400 (crankshaft position sensor replacement)
Crankshaft position sensor replacement, parts plus labor. This $200–$400 range is that sensor replacement. RepairPal's national average for the crankshaft position sensor is about $230–$335, with vehicle examples about $205–$375. Wiring, a connector, a short, an open, or a lost supply is not this sensor price and can land under it when the sensor tests good. A reluctor wheel is discussed on this page and is not included in this range.
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DIY vs shop
This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.