OBD-II trouble code
P0337: Crankshaft Position Sensor "A" Circuit Low Input
The crankshaft position sensor circuit is reading too low — the voltage the PCM sees has fallen below the expected window, often pointing at a short to ground, an open circuit, or a failed sensor. Because the crank signal is the engine's primary timing reference, a low-input fault frequently means a no-start or stall, and the fix usually lives in the sensor, its connector, or the wiring rather than deep in the engine.
Quick facts
- System
- Powertrain
- Category
- Sensors / Timing
- Severity
- High severity
- Drivable
- No — stop driving until repaired
- Repair cost range
- $130 – $700
- DIY difficulty
- Intermediate DIY
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).
A low-input reading usually traces to a circuit problem rather than a mechanical wheel issue. The common causes are a short to ground in the signal wire, an open circuit that collapses the signal, a connector that's corroded or loose, or a sensor that has failed and can no longer drive the circuit to its normal level. On three-wire (powered) crank sensors, a loss of supply voltage or a bad ground will also drag the output low. A poor air gap or a sensor mounted too far from the reluctor wheel can weaken the signal enough to read low as well. Because the level is wrong rather than the pattern, scope and meter testing of the circuit — checking for shorts, opens, supply, and ground — is the productive path.
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
- Excessive air gap or a sensor mounted too far from the reluctor wheel
- 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.Scope or meter the sensor output during cranking; a level that stays below spec confirms the low-input condition.
- 5.Check the air gap and mounting in case an excessive gap is weakening the signal.
- 6.Replace the sensor only after wiring, connector, supply, and ground all check out.
Repair cost
$130 – $700
A crankshaft position sensor replacement typically runs $150-$400 with labor, higher where access is poor. Repairing a shorted or open wire, or cleaning and re-pinning a connector, can be less. If a powered sensor's supply or ground circuit is at fault, the repair is wiring labor rather than a part. Because a low-input crank fault commonly causes a no-start, expect some diagnostic time to isolate circuit vs. sensor.
Estimate your repair
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Open the Repair Cost Estimator with crankshaft position sensor replacement preselected. Adjust labor rate and vehicle category to fit your situation.
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.