P0337 – Crankshaft Position Sensor “A” Circuit Low

System: Powertrain | Standard: ISO/SAE Controlled | Fault type: Circuit Low | Location: Designator A

Definition source: SAE J2012/J2012DA (industry standard)

P0337 indicates the powertrain control module has detected a low electrical condition in the Crankshaft Position Sensor “A” circuit. In practical terms, the module is seeing a signal or circuit level that is lower than expected for that sensor circuit during conditions when it should be providing a valid crankshaft position input. The exact monitor strategy, enabling conditions, and how quickly the code sets can vary by vehicle, so always confirm wiring diagrams, connector views, and test procedures in the correct service information. Because crankshaft position information is foundational for ignition and fuel control, a circuit-low fault can range from an occasional stumble to a no-start, depending on how severe or continuous the low condition is.

What Does P0337 Mean?

P0337 – Crankshaft Position Sensor “A” Circuit Low means the control module has identified a “low input” electrical fault on the crankshaft position sensor “A” circuit. Per standardized DTC structure conventions (SAE J2012), this is not a mechanical diagnosis by itself; it is an electrical/signal determination that the circuit is being pulled low, lacks proper feed, or is experiencing excessive voltage drop/high resistance that results in an abnormally low signal level. The fault points you toward the sensor circuit and its supporting wiring, power/ground (as applicable), and signal path to the module, rather than confirming a failed sensor without testing.

Quick Reference

• Subsystem: Crankshaft position sensor “A” signal circuit (and related power/ground or reference circuits, as applicable).
• Common triggers: Signal pulled toward ground, missing sensor feed, poor ground integrity, high resistance/voltage drop in wiring, or intermittent connection causing a persistently low signal.
• Likely root-cause buckets: Wiring/connector faults, sensor internal electrical fault, power/feed or ground issue, signal circuit short-to-ground, module input/circuit issue (less common).
• Severity: Often high; may cause hard starting, stalling, reduced power, or no-start depending on failure persistence.
• First checks: Visual inspection of harness routing and connector condition, verify secure seating/pin fit, check for rubbed-through wiring to ground, confirm power/ground integrity where applicable.
• Common mistakes: Replacing the sensor immediately without confirming a circuit-low condition, skipping voltage-drop checks, ignoring intermittent connector/pin issues, or overlooking harness chafing near the engine.

Theory of Operation

The crankshaft position sensor produces an electrical signal that represents crankshaft speed and position. Depending on vehicle design, the sensor may be a variable-reluctance type that generates an AC waveform, or a Hall-effect/magnetoresistive type that uses a power and ground to switch a digital signal. The control module monitors this input to determine engine timing and to confirm the engine is rotating.

For a “circuit low” fault, the module detects that the crankshaft position sensor “A” circuit remains at an unexpectedly low level, or the signal amplitude is too low to be interpreted reliably, during conditions when a valid signal should be present. Typical electrical reasons include a short-to-ground on the signal circuit, loss of sensor supply (where used), poor ground, or excessive resistance causing a low signal level at the module.

Symptoms

• No-start condition if the module cannot recognize crankshaft rotation.
• Stalling at idle or during deceleration if the signal drops low intermittently.
• Hard start or extended cranking time, especially when the fault is intermittent.
• Misfire or rough running due to unstable timing input.
• Reduced power or limited performance mode depending on control strategy.
• Tachometer erratic operation or dropping to zero if it relies on crank signal data.
• Warning light illumination with stored P0337 and possibly related crank signal codes.

Common Causes

• Short-to-ground on the crankshaft position sensor “A” signal circuit (damaged insulation, rubbed-through harness)
• High resistance in the signal circuit causing a pulled-low or weak signal (corrosion, moisture intrusion, poor terminal tension)
• Low sensor power/feed to the crankshaft position sensor (open in feed circuit, excessive resistance, shared feed issue)
• Sensor ground circuit problem creating low signal output (ground point corrosion, loose fastener, partially broken ground wire)
• Connector issues at the sensor or control module (backed-out pins, bent pins, contamination, poor pin fit)
• Crankshaft position sensor “A” internal fault producing a consistently low output
• Wiring damage near heat/moving components leading to intermittent low input during vibration or engine movement
• Control module input circuit issue (less common; consider after circuit and sensor tests verify good)

Diagnosis Steps

Tools that help: a scan tool that can read codes, freeze-frame, and live data; a digital multimeter for continuity and voltage-drop checks; and service information for connector pinouts and circuit routing (exact specifications vary by vehicle). Back-probing leads and basic hand tools for connector inspection are also useful. If available, a lab scope can help evaluate signal quality without relying on manufacturer-specific numeric thresholds.

1. Confirm the DTC and capture data: Retrieve all stored and pending codes and record freeze-frame data. Note whether the fault sets during cranking, idle, or while driving, since that helps focus on power/ground vs vibration-related wiring issues.
2. Check for related electrical DTCs: If there are additional powertrain sensor circuit low codes or module voltage codes, address shared power/ground or harness problems first to avoid chasing a symptom.
3. Perform a visual inspection (engine off): Inspect the crankshaft position sensor “A” connector, harness routing, and nearby looms. Look for chafing, oil saturation, contact with exhaust/heat, pin damage, corrosion, and signs of prior repairs. Correct obvious issues before further testing.
4. Connector integrity checks: With connectors accessible, verify terminals are fully seated and have proper retention. Inspect for spread terminals and contamination. Reseat connectors and ensure locking tabs are secure. Poor pin fit can create a low-input condition under vibration.
5. Clear codes and attempt to reproduce: Clear the DTC and attempt a controlled restart/road test while monitoring live data for engine speed/crank signal-related parameters (naming varies by vehicle). If the code resets immediately during cranking, prioritize feed/ground and hard shorts.
6. Wiggle test with live logging: With the engine idling (if possible) or during cranking, gently wiggle the harness at the sensor, at intermediate clips, and near the control module. Log live data and watch for sudden dropouts or changes that coincide with movement, indicating an intermittent short-to-ground or high resistance.
7. Check for short-to-ground on the signal circuit: Using the service wiring diagram, identify the signal circuit pin. With the sensor disconnected and the module connector accessed as needed (varies by vehicle), test the signal wire for continuity to ground. A short-to-ground strongly supports a circuit low fault and should be isolated by separating harness sections.
8. Verify sensor feed and ground integrity: Key on (and/or cranking as required by design), check that the sensor feed is present and that the ground path is intact. Use voltage-drop testing on the ground circuit under load (cranking if applicable) to find resistance at splices, connectors, or ground points. Do not rely on visual ground checks alone.
9. Check signal circuit for excessive resistance: With power off and connectors unplugged as appropriate, measure continuity end-to-end on the signal circuit and perform a drag/terminal tension check if service procedures allow. High resistance from corrosion or broken strands can bias the input low.
10. Evaluate the sensor as the suspect only after circuit checks: If power/feed, ground, and signal wiring tests pass (including wiggle testing), test per service information to determine whether the crankshaft position sensor “A” output is being pulled low by an internal fault. Replace the sensor only when circuit integrity is verified.
11. Last-check the control module input path: If all external wiring and the sensor are verified good, consider a module-side input issue or connector/pin damage at the module. Confirm pin fit and connector condition first. Module replacement or programming should be a final step and only after following service procedures.

Professional tip: A “circuit low” code is often caused by voltage drop or an unintended path to ground rather than a failed sensor. Prioritize loaded testing: perform voltage-drop checks on the sensor ground and feed while the circuit is operating (cranking/idle, as applicable), and repeat tests while manipulating the harness. This approach is more likely to reveal hidden resistance and intermittent shorts than static continuity checks alone.

Possible Fixes & Repair Costs

Repair costs for P0337 vary widely because the root cause can range from a simple wiring issue to component replacement or circuit repair. Total time and cost depend on access, required electrical testing, parts quality, and whether additional faults are present.

• Repair damaged wiring in the crankshaft position sensor “A” signal circuit (short-to-ground, pinched harness, chafed insulation) and secure routing to prevent recurrence
• Clean, dry, and reseat related connectors; correct poor terminal fit, corrosion, or backed-out pins to restore proper circuit integrity
• Restore proper power feed and ground integrity for the sensor circuit (repair opens, high resistance, or loose grounds verified by testing)
• Replace the crankshaft position sensor “A” only after circuit-low conditions are ruled out and sensor failure is confirmed by tests
• Repair or replace damaged reluctor/tone wheel-related components only if inspection confirms physical damage affecting signal generation (varies by vehicle design)
• Perform control module connector repairs or module replacement only after confirming the low-input condition is not caused by wiring, sensor, or power/ground issues

Can I Still Drive With P0337?

Driving with P0337 is not recommended if you experience stalling, a no-start condition, severe misfiring, reduced power, or any warning that affects braking or steering assist. A crankshaft position sensor “A” circuit low condition can cause unstable engine operation and unexpected shutdown. If the engine runs smoothly and the code is stored without symptoms, limit driving, avoid high-demand situations, and diagnose promptly to prevent a sudden stall.

What Happens If You Ignore P0337?

If P0337 is ignored, the vehicle may develop intermittent no-starts, random stalling, poor acceleration, or reduced power as the low-input signal condition worsens. Repeated stalls can create safety risks and may lead to additional fault codes, failed emissions readiness, and increased wear from misfires or unstable timing control. Electrical faults can also spread if a harness continues to rub or short.

Related Sensor Crankshaft Codes

Compare nearby sensor crankshaft trouble codes with similar definitions, fault patterns, and diagnostic paths.

• P0387 – Crankshaft Position Sensor “B” Circuit Low
• P0392 – Camshaft Position Sensor “B” Circuit Low Bank 2
• P0367 – Camshaft Position Sensor “B” Circuit Low Bank 1
• P0807 – Clutch Position Sensor Circuit Low
• P2962 – Intake Air Metering Control Valve Position Sensor Circuit Low
• P2618 – Crankshaft Position Signal Output Circuit Low

Key Takeaways

• P0337 indicates the crankshaft position sensor “A” circuit is being detected as a low input, not a confirmed mechanical failure.
• Most fixes start with wiring, connector, power, and ground checks before replacing parts.
• Intermittent shorts or poor terminal contact can mimic a failed sensor and should be verified with testing.
• Because a reliable crank signal is critical for engine control, symptoms can include stall or no-start.
• Prompt diagnosis reduces the chance of an unexpected shutdown and repeat failures.

Vehicles Commonly Affected by P0337

• Vehicles using a crankshaft position sensor “A” with a two-wire or three-wire engine speed input circuit (varies by vehicle)
• High-mileage vehicles with aging engine harness insulation and higher risk of chafing near the crank sensor area
• Vehicles frequently operated in wet, salty, or dusty environments that accelerate connector corrosion and terminal issues
• Vehicles with recent engine, transmission, or timing-related service where harness routing or connector seating may have been disturbed
• Vehicles with tight packaging around the engine where the crank sensor harness can contact hot or moving components
• Vehicles that have experienced prior electrical repairs, splice work, or aftermarket wiring changes near the powertrain harness
• Vehicles with oil leaks that can contaminate connectors or degrade harness materials over time
• Vehicles with underbody impact history where wiring near the engine or bellhousing area may be damaged (varies by layout)

FAQ

Does P0337 mean the crankshaft position sensor is bad?

No. P0337 means the module is detecting a crankshaft position sensor “A” circuit low condition. A failed sensor is only one possibility; wiring shorts to ground, poor connectors, power/ground problems, or high resistance causing signal collapse can produce the same low-input result.

Can a wiring short cause P0337 intermittently?

Yes. A harness that intermittently contacts ground due to engine movement, vibration, or heat-softened insulation can pull the signal low only under certain conditions. A wiggle test combined with live-data logging is often needed to reproduce and pinpoint the fault.

Will P0337 cause a no-start?

It can. Many engine control strategies require a valid crankshaft position signal to command ignition and fuel events. If the circuit low condition prevents the module from recognizing engine speed/position, the engine may crank but not start, or it may start and then stall.

Should I replace the sensor first to fix P0337?

Replacing the sensor first is a common mistake. Because this is a circuit-low fault, the priority is confirming whether the signal is being pulled low by wiring damage, poor terminal contact, or power/ground issues. Replace the sensor only after test results support sensor failure.

What should be checked first for a circuit low DTC like P0337?

Start with a careful visual inspection of the sensor connector and harness routing, then verify power feed and ground integrity, and check for a signal wire short-to-ground. Confirm findings with voltage-drop testing and live data rather than relying on parts swapping.

Verify all repairs by clearing the code, performing a road test under varied loads and temperatures, and confirming the crankshaft position signal remains stable without returning to a low-input condition.