An intermittent P0335 fault “Crankshaft Position Sensor ‘A’ Circuit No Signal” is one of the most frustrating drivability issues a professional mechanic faces. The engine runs fine one minute, then stumbles, stalls, or refuses to start the next, with no obvious pattern. Because the code doesn’t stay set or only appears under specific conditions (like cold starts or after highway driving), chasing it with basic scan-tool resets or sensor swaps rarely solves the problem. This is where a disciplined, step-by-step diagnostic procedure matters not just for accuracy, but for avoiding repeat comebacks and unnecessary parts replacement.

What does P0335 really mean in practice?

P0335 indicates the PCM isn’t receiving a valid crankshaft position signal during cranking or running. But crucially, the sensor itself may be fully functional. The fault often points to signal loss somewhere between the sensor and the PCM: damaged wiring, poor grounds, interference from aftermarket accessories, or even internal PCM communication glitches. That’s why simply replacing the crank sensor especially without verifying signal integrity at the connector is a common misstep. You’ll find more on this in our breakdown of why the engine speed signal can go missing even when the crankshaft sensor is operational.

When do you need this diagnostic approach?

You need this procedure when the P0335 sets intermittently say, only after the engine warms up, only on damp mornings, or only after hitting a bump. It also applies when the code returns quickly after sensor replacement, or when live data shows erratic or missing RPM while cranking (even though the engine spins normally). These are red flags that point beyond the sensor itself and into the circuit, connectors, or related systems like the camshaft position sensor or timing components.

How to test the crankshaft position signal properly

Start by checking the sensor’s reference voltage and ground at its connector with the key on, engine off don’t assume the harness is good just because it looks intact. Then use a lab scope to capture the actual AC waveform while cranking. A healthy 3x or 24x reluctor-style sensor should show clean, consistent peaks above ~100 mV. If the signal drops out, distorts, or flattens mid-crank, the issue is likely in the wiring, connector corrosion, or shielding failure not the sensor. Resist the urge to skip the scope: multimeter resistance checks alone miss intermittent opens and noise-induced dropouts.

What else can mimic or trigger an intermittent P0335?

Timing chain stretch or jump (especially on V6/V8 engines with dual variable valve timing), worn crank reluctor wheels, and even low battery voltage during cranking can all cause momentary signal loss. Aftermarket remote starters or alarm systems wired into the crank circuit are frequent culprits too they often introduce noise or create ground loops. Also check for oil contamination inside the sensor bore; sludge buildup can dampen the magnetic field enough to weaken the signal just enough to trigger P0335 under load or heat soak. For deeper analysis of persistent cases, see our guide on advanced troubleshooting after sensor replacement.

Common mistakes that waste time and money

  • Replacing the crank sensor first without verifying power, ground, and signal waveform
  • Using a generic “crank sensor tester” that only checks continuity not real-time signal integrity
  • Overlooking the camshaft position sensor: if its signal is missing or inconsistent, some PCMs will disable crank interpretation entirely and log P0335 as a downstream effect
  • Assuming the PCM is faulty before ruling out wiring faults, especially near heat sources like exhaust manifolds or turbochargers
  • Skipping the physical inspection of the reluctor wheel cracks, missing teeth, or bent mounting surfaces won’t show up on a scan tool

Real-world tip: Check the ground path, not just the sensor ground

The crank sensor usually shares a ground with other engine sensors often at the cylinder head or intake manifold. Corrosion or paint under that ground point breaks the entire cluster. Clean it down to bare metal, tighten the bolt to spec, and retest. This simple step resolves over 20% of intermittent P0335 cases we’ve tracked across shop reports. For more on how grounding, shielding, and modern bus architecture affect signal reliability, see our root cause analysis of missing engine speed signals.

Before moving to PCM diagnostics, verify these three things: (1) clean, stable reference voltage at the sensor connector with key on, (2) a clean, uninterrupted crank signal waveform on a scope during cranking, and (3) synchronized cam and crank signals in live data. If any one fails, don’t replace the PCM it’s almost certainly not the issue. If all three pass and P0335 still returns unpredictably, consider whether the vehicle has known PCM calibration quirks; some manufacturers issued TSBs for false P0335s on certain model years check OEM technical resources like TechAuthority before ordering a module.