OBD Code P0335: Crankshaft Position Sensor A Circuit – Causes, Symptoms & Fixes

When your vehicle’s diagnostic system triggers the P0335 code, it means the engine control module has detected a problem with the crankshaft position sensor circuit. This sensor is critical for engine operation—it tells your engine’s computer exactly where the crankshaft is positioned, which is essential for proper fuel injection timing, ignition timing, and overall engine management. Without accurate crankshaft position data, your engine cannot run efficiently or at all.

What Does P0335 Mean?

P0335 is a generic OBD-II diagnostic trouble code that stands for “Crankshaft Position Sensor A Circuit.” The “A” designation refers to the primary crankshaft position sensor circuit (vehicles with multiple sensors may also have a “B” circuit). This code is triggered when the engine control module fails to receive a valid signal from the crankshaft position sensor or detects an electrical fault in the sensor circuit.

The crankshaft position sensor works by detecting a reluctor ring or tone wheel on the crankshaft as it rotates. It generates a signal that the ECM uses to:

• Determine engine speed (RPM)
• Control fuel injection timing
• Control ignition timing
• Monitor for engine misfires
• Manage transmission shift points

When this sensor fails or its circuit is compromised, the engine cannot operate properly, and you’ll typically see a check engine light illuminated on your dashboard.

Common Symptoms

• Check Engine Light: The most obvious indicator; the light will remain on continuously or flash intermittently
• Engine Won’t Start: The vehicle may not crank or start at all, as the ECM cannot determine ignition timing
• Rough Idle: The engine may run very rough or unstably at idle speeds
• Stalling: The engine may stall while driving or at stops
• Loss of Power: Significant reduction in engine power and acceleration
• Hesitation During Acceleration: Delayed or jerky response when pressing the accelerator
• Transmission Issues: Automatic transmissions may shift erratically or refuse to shift
• Fuel Smell: Unburned fuel odor from the exhaust due to improper fuel injection timing
• Limp Mode: The vehicle may enter a reduced-power “limp home” mode to protect the engine

Possible Causes

P0335 can result from several issues, ranked from most to least common:

1. Faulty Crankshaft Position Sensor (Most Common)

The sensor itself has failed electrically or mechanically. This is the most frequent cause of P0335. Sensors can fail due to age, heat exposure, moisture intrusion, or manufacturing defects.

2. Damaged or Corroded Wiring/Connectors

The wiring harness connecting the sensor to the ECM may be damaged, corroded, or loose. Moisture, road salt, and vibration can degrade connections over time.

3. Poor Electrical Connection

A loose connector at the sensor or ECM, or corroded terminals, can interrupt signal transmission. This is especially common in older vehicles or those exposed to harsh weather.

4. Reluctor Ring Damage

The tone wheel or reluctor ring on the crankshaft may be damaged, cracked, or worn, preventing the sensor from reading the crankshaft position accurately.

5. ECM Software Issues or Failure

Less common, but the engine control module itself may have corrupted software or a hardware failure. This typically requires module reprogramming or replacement.

6. Timing Chain or Belt Issues

If the timing chain has stretched or the timing belt has slipped, the crankshaft position may be misaligned, causing sensor signal errors.

7. Engine Mechanical Problems

In rare cases, internal engine damage or a seized crankshaft can cause the sensor to fail or produce an abnormal signal.

Diagnostic Steps

Follow these steps to diagnose a P0335 code:

Step 1: Retrieve and Document the Code

Use an OBD-II scanner to read the code and any additional freeze frame data. Note the conditions when the code was triggered (speed, temperature, load, etc.). Clear the code and see if it returns—a recurring code indicates a persistent problem.

Step 2: Visual Inspection

Locate the crankshaft position sensor (usually mounted near the crankshaft pulley or on the engine block). Inspect for:

• Physical damage or cracks
• Loose or corroded connectors
• Damaged wiring or insulation
• Oil leaks that may have contaminated the sensor

Step 3: Check Connector and Wiring

Disconnect the sensor connector and inspect for corrosion, bent pins, or moisture. Clean the connector with electrical contact cleaner. Reconnect firmly and test again. Use a multimeter to check for proper voltage and ground at the connector.

Step 4: Test Sensor Resistance

With the engine off, use a multimeter to measure the sensor’s resistance. Compare the reading to your vehicle’s specifications (typically 200–900 ohms, depending on sensor type). Out-of-spec readings indicate a faulty sensor.

Step 5: Test Sensor Output Signal

Using an oscilloscope or advanced scanner, monitor the sensor’s AC voltage output while cranking the engine. The signal should show a consistent waveform pattern. No signal or an erratic pattern indicates sensor failure.

Step 6: Check Reluctor Ring

If the sensor tests good, visually inspect the reluctor ring on the crankshaft for damage, cracks, or missing teeth. This may require removing the crankshaft pulley or timing cover.

Step 7: Test ECM and Wiring

If the sensor and reluctor ring are good, test the wiring harness for continuity, shorts, and proper voltage supply to the sensor. Use a wiring diagram specific to your vehicle. If wiring is good, the ECM may need reprogramming or replacement.

Repair Cost Estimates

Repair costs for P0335 vary significantly based on the root cause and your vehicle:

• Crankshaft Position Sensor Replacement: $150–$400 (parts and labor combined). Parts typically cost $50–$150, with labor ranging from $100–$300 depending on sensor location accessibility.
• Wiring Repair or Connector Replacement: $50–$200 for simple fixes like connector cleaning or terminal replacement. More extensive wiring repairs may cost $200–$400.
• Reluctor Ring Replacement: $300–$800, as this often requires crankshaft removal and significant labor.
• ECM Reprogramming: $200–$600 if software corruption is the issue.
• ECM Replacement: $800–$2,000+ if the module has failed and cannot be repaired.

Note: Luxury and European vehicles typically cost more due to specialized diagnostic equipment and labor rates. Always get a diagnostic fee quote before authorizing repairs.

Can I Still Drive?

Severity: HIGH

You should not drive a vehicle with an active P0335 code, or only drive it directly to a repair facility. Here’s why:

• Engine May Not Start: In many cases, the engine won’t start at all, leaving you stranded.
• Sudden Stalling: The engine may stall without warning while driving, creating a dangerous situation, especially on highways or in traffic.
• Loss of Power: Reduced engine power may prevent you from accelerating safely or merging in traffic.
• Transmission Issues: Erratic shifting can cause loss of power or unexpected acceleration.
• Limp Mode Restrictions: Your vehicle may be limited to low speeds, making it unsafe for highway driving.
• Catalyst Damage: Prolonged driving with this code can cause unburned fuel to damage the catalytic converter, leading to much more expensive repairs.

If your vehicle is drivable, proceed carefully to a repair shop. Avoid highway driving and heavy traffic. If the engine stalls or won’t start, call a tow truck.

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