OBD Code P0337: Crankshaft Position Sensor Signal Too Low

The P0337 diagnostic trouble code is a high-severity ignition system fault that affects engine timing and fuel injection. When your vehicle’s engine control module (ECM) detects that the crankshaft position sensor signal voltage is below the acceptable threshold, it triggers this code and illuminates the check engine light. This is a critical sensor for engine operation, and ignoring this code can lead to severe drivability issues or engine damage.

What Does P0337 Mean?

P0337 stands for “Crankshaft Position Sensor ‘A’ Circuit Low.” The crankshaft position sensor is a critical component that monitors the rotational speed and position of the engine’s crankshaft. It sends this information to the engine control module, which uses it to:

• Determine the correct ignition timing
• Control fuel injection timing
• Manage transmission shift points
• Detect engine misfires

When the ECM receives a voltage signal from the CKP sensor that falls below its minimum acceptable range (typically below 0.2 volts), it stores the P0337 code. This low signal condition prevents the engine from operating properly because the ECM cannot accurately determine crankshaft position and speed.

Common Symptoms

• Check Engine Light: The most immediate indicator; the light will remain on continuously
• Engine Stalling: The engine may stall while driving or at idle without warning
• No Start Condition: The engine may crank but refuse to start, or start intermittently
• Rough Idle: Noticeable vibration and instability when the vehicle is stopped
• Loss of Power: Significant reduction in acceleration and overall engine performance
• Hesitation: Delayed throttle response and jerky acceleration
• Transmission Issues: Hard shifts, delayed shifts, or transmission warning lights
• Backfiring: Popping sounds from the exhaust due to incorrect ignition timing

Possible Causes (Ranked by Frequency)

1. Faulty Crankshaft Position Sensor (Most Common) – The sensor itself has failed internally or its output circuit has degraded, causing it to send a weak or no signal. This accounts for approximately 70-80% of P0337 cases.
2. Corroded or Damaged Wiring/Connectors – Corrosion, water intrusion, or physical damage to the CKP sensor wiring harness or connector can reduce signal voltage. Poor connections create resistance that drops the signal below acceptable levels.
3. Broken or Loose Connector – A loose or improperly seated connector at the sensor or ECM can interrupt the signal path or cause intermittent contact.
4. Engine Oil Contamination – Dirty or contaminated engine oil can cause the sensor to malfunction, particularly if it’s an inductive-type sensor with a gap that’s affected by debris.
5. Faulty Engine Control Module (PCM/ECM) – Though rare, a defective ECM can misinterpret a normal sensor signal as too low. This typically occurs only after other causes have been ruled out.
6. Wiring Harness Short or Open Circuit – A break in the signal wire or a short to ground can prevent the sensor signal from reaching the ECM at proper voltage levels.
7. Timing Belt or Chain Issues – In some cases, a slipping timing belt or chain can cause the sensor to send inconsistent signals, though this is less common for a purely “low signal” code.

Diagnostic Steps

Step 1: Retrieve Full Diagnostic Information

• Use an OBD-II scanner to read all stored and pending codes
• Note any additional codes that may point to related issues (P0336, P0338, P0339)
• Check for freeze frame data to understand conditions when the fault occurred

Step 2: Visual Inspection

• Locate the crankshaft position sensor (typically near the crankshaft pulley, timing cover, or transmission bell housing—consult your vehicle’s service manual for exact location)
• Inspect the sensor connector for corrosion, water damage, or loose pins
• Check the wiring harness for cuts, abrasions, or signs of damage
• Ensure the connector is fully seated and latched

Step 3: Voltage Testing

• With the ignition key ON (engine off), use a multimeter to measure voltage at the CKP sensor connector
• Compare the reading to manufacturer specifications (typically 4.5-5.5V for the reference voltage)
• If voltage is below 0.2V or absent, suspect a wiring or connector issue
• With the engine cranking, the signal voltage should fluctuate; if it remains static or low, the sensor is likely faulty

Step 4: Resistance Testing

• Disconnect the CKP sensor and measure its resistance with an ohmmeter
• Compare to manufacturer specifications (typically 200-900 ohms for inductive sensors)
• Out-of-range resistance indicates a faulty sensor

Step 5: Wiring Continuity Test

• With the sensor disconnected, test the signal wire for continuity from the sensor connector to the ECM
• Test for shorts to ground or power
• Broken or shorted wires require repair or replacement

Step 6: Sensor Replacement and Retest

• If all wiring tests pass but voltage is still low, replace the crankshaft position sensor
• Clear the code and perform a test drive to confirm the repair
• If the code returns, suspect an ECM issue or wiring that was missed

Repair Cost Estimates

• Crankshaft Position Sensor Replacement: $150–$400 (parts + labor)
  • Sensor part cost: $50–$200
  • Labor: 0.5–2 hours depending on sensor location
• Wiring Repair/Connector Replacement: $100–$300
  • Simple connector replacement: $50–$150
  • Wiring harness repair or replacement: $150–$400
• Engine Control Module (ECM) Replacement: $500–$1,500+ (rare)
  • Only necessary if sensor and wiring are confirmed good
  • May require reprogramming

Can I Still Drive?

Severity: HIGH – Not Recommended for Extended Driving

While you may be able to start and drive the vehicle in some cases, P0337 is a serious fault that should be addressed promptly:

• Immediate Risk: The engine may stall without warning, creating a safety hazard, especially in traffic or on highways
• Drivability: Poor acceleration, rough idle, and hesitation make the vehicle unsafe to operate
• Engine Damage: Prolonged driving with incorrect ignition timing can damage the engine, catalytic converter, and transmission
• Recommendation: Have the vehicle diagnosed and repaired as soon as possible. If you must drive it, do so only to a repair facility and avoid highways or heavy traffic

Frequently Asked Questions