Crankshaft Position Sensor A Circuit
The Powertrain Control Module (PCM) uses the crankshaft position sensor to determine engine RPM and crankshaft position for accurate spark and fuel timing. Code P0335 is set when the PCM detects no signal or an erratic signal from the 'A' circuit of the crankshaft position sensor for a predetermined amount of time.
This code is highly urgent because the engine relies on the crankshaft position sensor to operate. A failure in this circuit can cause the engine to stall unexpectedly while driving or prevent the vehicle from starting entirely.
Common symptoms
- Engine cranks but will not start (no-start condition)
- Engine stalls intermittently while driving or idling
- Rough idling, hesitation, or engine misfires
- Check Engine Light is illuminated
- Tachometer drops to zero or behaves erratically while the engine is running
Likely causes
- Faulty crankshaft position sensor
- Damaged, corroded, or loose wiring and connectors in the sensor circuit
- Damaged reluctor ring (crankshaft tone ring) missing teeth or covered in debris
- Incorrect sensor air gap (if adjustable)
- Faulty Powertrain Control Module (PCM) (rare)
What to check before replacing parts
Perform a visual inspection of the sensor wiring and connector
Look for: Look for frayed wires, melted insulation, oil contamination, or corrosion at the sensor connector that would cause an open or short circuit.
Monitor engine RPM with a scan tool while cranking
Look for: Observe the live data for engine RPM; if it reads 0 RPM while the engine is actively cranking, the sensor is not sending a signal to the PCM.
Test the sensor's internal resistance or power supply
Look for: Using a multimeter, verify that a Hall-effect sensor has the correct reference voltage (usually 5V or 12V) and ground, or check a VR sensor's internal resistance against factory specifications.
Analyze the sensor signal using an oscilloscope
Look for: Back-probe the sensor signal wire while cranking or running. Look for a clean, consistent square wave (Hall-effect) or sine wave (VR) without dropouts, noise, or irregular amplitude.
Inspect the crankshaft reluctor (tone) ring
Look for: Remove the sensor and inspect the tone ring through the mounting hole. Look for missing teeth, physical damage, or excessive metallic debris that could disrupt the magnetic field.
This page explains the generic P0335 definition and is general reference information, not a diagnosis for your specific vehicle. Actual causes, severity, and repairs vary by make, model, engine, and mileage — always confirm with a scan tool and a qualified technician before replacing parts.
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