P0337
Crankshaft Position Sensor A Circuit Low InputP0337 is a generic OBD-II powertrain diagnostic trouble code: Crankshaft Position Sensor A Circuit Low Input. It is logged by the engine control unit when the ckp/cmp monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P0337 means
P0337 indicates the powertrain control module (PCM) has detected a signal voltage from Crankshaft Position Sensor "A" that is persistently below the acceptable lower threshold. The CKP sensor monitors the rotational position and speed of the crankshaft via a toothed reluctor wheel, and the PCM relies on this signal every engine cycle to calculate fuel injection timing and ignition spark events.
On Hall-effect sensor designs, a circuit open or short to ground will pull the output line low and hold it there, starving the PCM of any RPM signal. On variable-reluctance (VR) coil sensors, an open coil winding produces a severely attenuated AC waveform that reads below threshold. The most common hardware failures are: internal sensor coil collapse, corrosion or water intrusion at the sensor connector that shorts the signal wire to chassis ground, and chafed harness sections near hot or vibrating components. Because the PCM cannot fire injectors without a valid CKP signal, a continuous P0337 typically results in a no-start; even when the fault is borderline, driveability suffers badly with misfires, stalling, and loss of tachometer signal.
Common causes
Most-frequently reported root causes when P0337 is logged.
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1
Faulty CKP sensor with failed internal coil or Hall-effect element producing sub-threshold voltage
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2
Harness short to ground — chafed insulation or pinched wire between sensor and PCM
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3
Corroded, loose, or water-contaminated sensor connector reducing signal voltage
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4
Damaged or missing reluctor wheel teeth preventing normal waveform generation
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5
Open circuit in the sensor signal or ground return wire
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6
Low system voltage (weak battery or alternator) dropping sensor reference supply below operating range
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7
Failed PCM input stage misreading a valid signal as low
Symptoms drivers notice
How to diagnose P0337
A typical diagnostic flow when this code is present.
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1
Scan for all stored codes and freeze-frame data; note whether RPM reads zero during cranking on the scan tool live data
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2
Perform a thorough visual inspection of the CKP sensor connector and harness for chafing, oil contamination, corrosion, or melted insulation
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3
With the connector unplugged, measure sensor resistance (VR type: typically 800–2000 Ω) or check supply and ground at the connector (Hall type: 5 V reference, clean ground, signal wire)
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4
Inspect the reluctor wheel through the sensor bore for bent, missing, or debris-coated teeth
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5
Using an oscilloscope, crank the engine and verify the sensor waveform amplitude and pattern — low or flat waveform confirms sensor or harness fault
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6
Check battery voltage and charging system before condemning the sensor; voltage below 10 V during cranking can trigger false CKP codes
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7
Replace sensor if waveform is absent or severely attenuated and wiring checks pass; clear codes and confirm repair with a test drive
Related powertrain codes
- P000A — A Camshaft Position Slow Response Bank 1
- P000B — B Camshaft Position Slow Response Bank 1
- P000C — A Camshaft Position Slow Response Bank 2
- P000D — B Camshaft Position Slow Response Bank 2
- P0010 — A Camshaft Position Actuator Circuit (Bank 1)
- P0011 — A Camshaft Position - Timing Over-Advanced or System Performance (Bank 1)
Frequently asked questions
Can I drive with P0337 active?
Generally no. If the PCM has lost the CKP signal entirely, the engine will not start or will stall immediately. Even with a borderline low signal the risk of a sudden no-start while moving makes driving unsafe until the fault is repaired.
Will a weak battery cause P0337?
Yes. If cranking voltage drops below roughly 9–10 V, the CKP sensor reference supply may sag enough that the signal falls below the PCM's low threshold. Always verify battery and charging system health before replacing the sensor.
How do I tell if it is the sensor or the wiring?
Unplug the sensor and measure resistance across the signal terminals (VR type) or check for clean 5 V reference and ground (Hall type). Then back-probe the harness at the PCM connector to confirm continuity and verify no short to ground exists on the signal wire.
Is P0337 the same as P0335?
They are closely related. P0335 is a general CKP A circuit malfunction (any fault type), while P0337 specifically indicates the signal is stuck or consistently low. P0338 is the complementary high-input code.
Disabling P0337 in software
RaceTune can permanently disable P0337 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
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