1996 Chevrolet Impala P0335 Crankshaft Position Sensor Code: Diagnosis and Fix After Engine Rebuild

The P0323 code indicates a mismatch between the high-resolution and low-resolution distributor signals. The PCM expects a 45:1 frequency ratio — the high resolution signal should be exactly 45 times stronger than the low resolution one. To verify this, check the red-BK (low-res) and PL-WT (high-res) wires at the distributor using an oscilloscope. If either signal is missing or out of phase, the issue lies in the distributor. A good scan tool should display both signals — a lab scope is essential for accurate diagnosis. Did your mechanic use an oscilloscope to test these signals? This is critical for confirming whether it's the distributor or another component.

No, I actually received a P0335 code — Crankshaft Position Sensor Range/Performance. I was told that if RPMs are displayed on the dash, the sensor is likely fine and the issue must be either a timing chain tooth misalignment or a faulty distributor. Since this engine was rebuilt, I don’t believe the timing chain is worn, but I’m not entirely sure. Could a loose or damaged timing chain still cause this code?

P0335 — Crankshaft Position Sensor (CKP) — is located in the engine front cover and works with a 4X reluctor wheel on the crankshaft. As the crank rotates, teeth interrupt a magnetic field, generating a signal read by the PCM to monitor crank velocity for misfire detection. The PCM compares the CKP sensor signal with low-resolution (LR) and high-resolution (HR) distributor signals. During normal operation, at the falling edge of a CKP pulse, the PCM counts HR pulses until it detects the next LR pulse — this should result in a 45:1 ratio. The scan tool parameter 'CKP:Lo Resolution Angle' shows camshaft deviation from crank alignment; under normal conditions, this value should be near zero degrees. Conditions for setting P0335: - Engine speed between 500–4000 RPM (LT1) or 675–4000 RPM (LT4) - Ignition voltage between 9–17 volts - CKP:Lo Resolution Angle outside -21° to +51° range - No signal from the CKP sensor Possible causes: - Loose or corroded sensor connections - Excessive timing chain or gear wear - Distributor backlash or mechanical issues - Crank reluctor wheel damage or improper installation - Sensor touching the reluctor wheel To diagnose properly, you must use a lab scope to observe all three signals — crank, low-res, and high-res — simultaneously. Alldata provides only basic data; actual signal waveforms are required for accurate diagnosis.

Thanks for the detailed explanation! I’ve used my scan tool and noticed that at idle, the timing is significantly retarded — around 20–25 degrees. I assumed this was due to the check engine light being on. When driving, the car feels weak in mid-throttle zones and starts to hesitate when accelerating slightly above 60 mph without downshifting — it seems to 'start moving' then develop small misfires. These symptoms align with timing or sensor issues. Are these all symptoms of a faulty distributor or timing chain? Any confirmation on whether P0335 is the root cause?

It’s likely the optical distributor causing the issue. The PCM uses the crankshaft position signal to detect engine speed and monitor for misfires — not directly for spark or fueling. If the distributor signals are inconsistent, it will trigger P0335 even if the sensor is fine. For a definitive diagnosis, take it to a certified diagnostic shop that can scope both low and high-resolution distributor signals using an oscilloscope.

I replaced the OptiSpark distributor, but the P0335 code returned shortly after restarting. The car runs slightly better, but the issue persists. My scan tool shows cylinder 1 consistently at -20 to -40 degrees across all RPMs — a significant deviation from normal. All components were replaced during the rebuild: plugs, wires, sensors, and distributor. I’m now unsure what else could be wrong. Any additional troubleshooting steps or possible mechanical causes?

Did your mechanic connect an oscilloscope to both the low and high-resolution signals from the distributor? What type of scan tool do you currently have? Does your mechanic use a professional-grade diagnostic tool capable of displaying real-time signal waveforms and CKP:Lo Resolution Angle data?

The Crankshaft Position Sensor is mounted in the engine front cover and works with a 4X reluctor wheel on the crankshaft. As the crank rotates, teeth interrupt a magnetic field, generating a signal read by the PCM to detect misfires. The PCM monitors the CKP sensor signal along with low-resolution (LR) and high-resolution (HR) distributor signals. At the falling edge of a CKP pulse, it begins counting HR pulses until detecting the next LR pulse — this should result in a 45:1 ratio. The 'CKP:Lo Resolution Angle' parameter shows camshaft deviation from crank alignment; normal operation should show near-zero values. Key diagnostic questions: - Does your scan tool display CKP:Lo Resolution Angle and cylinder misfire index? - Does it read manufacturer-specific codes? - Has your mechanic used an oscilloscope to check the crank signal and both low/high resolution distributor signals? Without these, diagnosis remains speculative.

If the high-resolution signal circuit becomes open or grounded, a P0372 code will appear — leading to reduced performance and poor fuel economy. Also, check for excessive crankshaft timing (long crank times). The distributor has a fresh air vent system that relies on engine vacuum to maintain proper internal pressure. If this system is blocked or inoperative, it can cause premature failure of the distributor. Ensure this system is functioning properly before concluding the issue is mechanical.