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The crankshaft position sensor (CKP sensor) is one of the most critical components in your car’s engine management system. It monitors the crankshaft’s speed and position, sending this information to the Engine Control Module (ECM). How do I know if my crankshaft is bad? If it fails, your engine’s timing, fuel injection, and ignition can all go haywire. This atricle will show you five common symptoms of a bad crankshaft position sensor.
Recognizing the early symptoms of a bad crankshaft position sensor can help you avoid costly breakdowns and prevent further engine damage.
1. Engine Stalling or Sudden Shutdown
One of the most alarming signs of a failing crankshaft sensor is random stalling while driving or at idle. When the ECM loses crankshaft data, it may shut off fuel injection or spark to protect the engine. In some cases, the car will restart immediately; in others, you may need to wait until the sensor cools down.
Why it happens: The CKP sensor’s internal circuitry can become heat-sensitive, causing intermittent signal loss.
2. Hard Starting or No-Start Condition
A bad crankshaft sensor can prevent your car from starting altogether. Without accurate crankshaft position data, the ECM cannot determine when to fire the spark plugs or inject fuel.
Typical scenario: You turn the key, the engine cranks, but it never fires up. This symptom is often misdiagnosed as a fuel pump or ignition coil issue.
3. Check Engine Light (CEL) Illumination
A failing CKP sensor often triggers a Check Engine Light, usually accompanied by OBD-II codes like P0335 (Crankshaft Position Sensor “A” Circuit).
Using an OBD2 scanner, you can confirm if the crankshaft sensor is the culprit.
Pro tip: If your CEL is on, scan your vehicle immediately—continuing to drive with a failing CKP sensor can cause further issues.
4. Engine Misfires or Poor Performance
When the crankshaft sensor sends erratic signals, the ECM may fire spark plugs at the wrong time or inject fuel inconsistently. This leads to misfires, hesitation, or a noticeable loss of power—especially during acceleration.
Impact on fuel economy: Poor ignition timing can make your engine burn more fuel than necessary.
5. Reduced Fuel Efficiency
A bad CKP sensor disrupts the engine’s optimal air-fuel mixture. Over time, this not only reduces MPG but can also increase harmful emissions, potentially causing your car to fail an emissions test.
How to Confirm the Problem with an OBD2 Scanner
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Plug the OBD2 scanner into your car’s diagnostic port.
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Turn the ignition to the “ON” position (engine off).
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Select “Read Codes” from the menu.
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Look for crankshaft-related codes like P0335 or P0336.
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If found, inspect the sensor and wiring before replacement.
💡 Pro Tip: The CGSULIT SC880 and SC530 OBD2 scanners can read manufacturer-specific codes for multiple brands, making it easier to confirm crankshaft sensor issues without guesswork.
Final Thoughts
If you notice any of these symptoms, don’t wait—diagnose the issue as soon as possible. In many cases, replacing the crankshaft position sensor will restore your car’s performance and prevent a complete breakdown.
FAQs About Crankshaft Position Sensor Problems
Q1: What are the most common symptoms of a bad crankshaft position sensor?
The most common symptoms include engine stalling, difficulty starting, poor acceleration, reduced fuel economy, and an illuminated check engine light.
Q2: Can a bad crankshaft position sensor cause engine misfires?
Yes. A faulty crankshaft sensor can disrupt ignition timing, leading to engine misfires, rough idling, or sudden power loss.
Q3: Will an OBD2 scanner detect a bad crankshaft position sensor?
Yes. Most OBD2 scanners can read trouble codes like P0335, which point directly to crankshaft position sensor issues and help confirm the diagnosis.
Related Article:
How to Relearn Crankshaft Sensor Position with an OBD2 Scanner?
Crankshaft Maintenance: Tips for Longevity