P0337 medium Severity

P0337: Crankshaft Position Sensor A Circuit Low Input

May cause hard starting, rough idle, stalling, or no‑start conditions due to weak or missing crankshaft position signal impacting ignition timing and fuel delivery.

Overview

P0337 indicates a low voltage signal from the crankshaft position sensor circuit, often caused by wiring issues, sensor failure, or reluctor ring damage. Symptoms include hard start, rough idle, and engine performance issues.

Common Symptoms

  • Check Engine Light illuminated
  • Hard starting or no start
  • Rough or erratic idle
  • Reduced engine power or hesitation
  • Engine stalling under load or at idle

Most Common Causes

Faulty crankshaft position sensor high

Sensor output voltage weak or absent triggering low input detection.

Damaged or corroded wiring / connectors in CKP sensor circuit high

Shorts or opens in harness drop signal voltage or disrupt reference/ground paths.

Reluctor ring damage or excessive air gap medium

Physical damage or misalignment reduces sensor signal amplitude.

Poor sensor ground or low reference voltage medium

Weak reference or ground increases circuit resistance and lowers signal.

PCM/ECM input stage failure low

Rare; considered after wiring and sensor checks are complete.

Diagnostic Steps

  1. Connect OBD‑II scanner and confirm P0337; check for related codes.
    Expected: P0337 with potential complementary codes (e.g., P0335/P0338).
    Interpretation: Verifies fault and identifies additional sensor circuit issues.
  2. Visually inspect CKP sensor harness and connector for damage or corrosion.
    Expected: No broken wires, corrosion, or loose pins.
    Interpretation: Damage here can directly cause low signal.
  3. Back‑probe sensor connector; measure reference voltage and ground.
    Expected: Stable reference ~5V and good ground continuity.
    Interpretation: Low or unstable reference/ground indicates wiring or ECU issue.
  4. Measure sensor output voltage or waveform during cranking/running.
    Expected: Consistent square/sine wave above low threshold.
    Interpretation: Weak/no waveform confirms sensor or reluctor ring issue.
  5. Inspect reluctor ring for missing teeth or excessive air gap.
    Expected: Properly intact ring with correct gap.
    Interpretation: Physical defects here degrade signal quality.
  6. If all checks pass, test PCM input circuit.
    Expected: Correct signal interpretation at PCM.
    Interpretation: Fault here suggests PCM internal fault (rare).

Repair Solutions

Replace crankshaft position sensor medium
Estimated Cost: $50 - $300

Typical OEM sensor costs vary by vehicle; replace with correct part.

Repair or replace wiring harness/connectors medium
Estimated Cost: $30 - $200

Fix shorts/opens and ensure corrosion‑free connections.

Clean or replace reluctor ring and adjust air gap hard
Estimated Cost: $100 - $500

May require significant engine teardown on some models.

Repair or replace PCM/ECM hard
Estimated Cost: $600 - $1200

Considered only after sensor and wiring are verified good.

Common Misdiagnoses

Avoid these common diagnostic mistakes:

  • Replacing crankshaft sensor without testing wiring and reference/ground circuits
  • Assuming unrelated misfire codes are root cause without verifying crank signal
  • Ignoring reluctor ring damage as potential cause

Frequently Asked Questions

Technical definition of P0337 OBD-II Code

The P0337 code stands for Crankshaft Position Sensor A Circuit Low Input. This generally indicates an issue with the Sensors system.

How serious is the P0337 code?

With a severity level of medium, may cause hard starting, rough idle, stalling, or no‑start conditions due to weak or missing crankshaft position signal impacting ignition timing and fuel delivery.

What are the symptoms of P0337?

You may experience the following: Check Engine Light illuminated, Hard starting or no start, Rough or erratic idle.

What parts fail when P0337 is set?

It can be caused by several factors, most notably: Faulty crankshaft position sensor, Damaged or corroded wiring / connectors in CKP sensor circuit, Reluctor ring damage or excessive air gap.

What is the price difference for fixing P0337?

Repair costs depend on the specific failure. A simple Repair or replace wiring harness/connectors replacement is relatively affordable ($30-$200), whereas a Repair or replace PCM/ECM repair is more expensive, potentially reaching $1200.

Is P0337 a generic or manufacturer-specific code?

Yes, P0337 is a generic code that applies to all OBD-II compliant vehicles, including Ford, Toyota, Honda, Chevrolet, Nissan, Dodge, BMW, and more.

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