P0335

Crankshaft Position Sensor A Circuit Malfunction

P0335 is a generic OBD-II powertrain diagnostic trouble code: Crankshaft Position Sensor A Circuit Malfunction. It is logged by the engine control unit when the ckp/cmp monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
P0335
Group
Powertrain
System
CKP/CMP
Severity
Critical (limp mode / no-start)
Need P0335 disabled?
RaceTune permanently disables any OBD-II trouble code on supported ECUs — for motorsport, off-road, and export use.
→

What P0335 means

P0335 is set when the powertrain control module (PCM) detects an absent, erratic, or implausible signal from the crankshaft position (CKP) sensor 'A' circuit. The CKP sensor monitors a toothed reluctor ring mounted on the crankshaft and generates a pulsed voltage signal that the PCM uses to determine engine speed (RPM) and the rotational position of the crankshaft relative to cylinder #1 top dead centre. This data is fundamental to calculating precise ignition spark timing and fuel injection pulse width.

Without a valid CKP signal the PCM cannot synchronise the ignition and injection events, making the engine impossible to start or causing it to stall immediately after firing. On some platforms the PCM can fall back to estimating crank position from the camshaft position (CMP) sensor signal, permitting limited operation but typically with noticeably degraded performance, rough idle, and poor throttle response. The code will illuminate the MIL and may trigger a no-start or limp condition depending on the vehicle.

The fault may be caused by a failed sensor element, damaged or corroded wiring between the sensor and PCM, an incorrectly gapped sensor relative to the reluctor ring, a missing or damaged reluctor ring tooth, or electrical interference injected onto the signal wire by a failing alternator. Because the CKP signal is critical to engine operation, prompt diagnosis is strongly advised to avoid being stranded or causing secondary damage from erratic timing events.

Common causes

Most-frequently reported root causes when P0335 is logged.

  • 1
    Faulty crankshaft position sensor (open circuit, short circuit, or internal corrosion)
  • 2
    Damaged, chafed, or broken wiring in the CKP sensor harness
  • 3
    Corroded or loose sensor connector causing intermittent signal loss
  • 4
    Incorrect sensor air gap to the reluctor ring (outside 0.5–1.5 mm typical spec)
  • 5
    Missing, damaged, or worn reluctor ring tooth on the crankshaft
  • 6
    Electrical interference from a failing alternator (shorted diode or stator winding)
  • 7
    Rodent damage to the sensor wiring harness
  • 8
    PCM failure or damaged PCM input circuit (rare)

Symptoms drivers notice

Malfunction indicator lamp (MIL / check engine light) illuminated
Engine cranks but will not start, or starts and immediately stalls
Hard starting, especially when the engine is warm
Rough idle and engine hesitation or stumbling under acceleration
Tachometer reads zero or behaves erratically while cranking
Engine stalls unexpectedly at low speed or while idling

How to diagnose P0335

A typical diagnostic flow when this code is present.

  1. 1
    Connect a scan tool, retrieve all stored DTCs, and note any freeze-frame data to identify conditions present when P0335 was set
  2. 2
    Perform a thorough visual inspection of the CKP sensor, its connector, and the wiring harness — look for chafing, corrosion, melted insulation, rodent damage, and loose connector locks
  3. 3
    Measure sensor resistance with a multimeter (refer to OEM spec; typically 200 Ω–2 kΩ for magnetic VR sensors); an open or near-zero reading indicates sensor failure
  4. 4
    With a lab scope or graphing multimeter, observe the CKP signal waveform while cranking — look for missing pulses, erratic amplitude, or no output at all
  5. 5
    Inspect the reluctor ring through the sensor port or with a mirror/borescope for missing, cracked, or excessively worn teeth
  6. 6
    Check alternator output waveform for AC ripple, which can corrupt the CKP signal on the same harness bundle
  7. 7
    Clear the DTC, road-test or crank the engine to confirm the fault is resolved before returning the vehicle to service

Related powertrain codes

Frequently asked questions

Can I drive with a P0335 code?

Driving is not recommended. Without a valid crankshaft position signal the engine may stall without warning at any speed, creating a safety hazard. Some vehicles enter a limp mode using camshaft position data, but performance will be severely degraded and a no-start condition can occur at any time.

Will P0335 always prevent the engine from starting?

Not always. Many modern PCMs can substitute camshaft position data for a limited time, allowing the engine to start and run poorly. However, if the CKP signal is completely absent the engine will not start regardless of cam signal availability.

How do I confirm the CKP sensor itself is bad rather than the wiring?

Measure the sensor's resistance and, if it is a variable-reluctance type, compare it to the OEM specification. Then backprobe the signal wire at the PCM connector while cranking to confirm whether the signal is present at the PCM end. If a clean signal appears at the sensor but not at the PCM, the fault is in the harness, not the sensor.

Can a bad alternator really cause P0335?

Yes. A failing alternator with a shorted diode or stator winding injects AC ripple onto the charging circuit. If the CKP sensor wiring runs near the alternator output cable or shares a ground, this ripple can corrupt the sensor signal and set P0335 — particularly noted on certain Ford trucks. Testing alternator AC ripple with a multimeter is a worthwhile diagnostic step if the sensor and wiring check out.

Disabling P0335 in software

RaceTune can permanently disable P0335 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.

Permanent
The monitor is disabled in the ECU itself — not just cleared. It cannot return.
Tailored to your file
Each patch is matched to your specific software version — never a one-size-fits-all file.
Reversible
The original file is always preserved. Reflash the stock to return the ECU to factory state.

Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.

Got P0335 in your scan?

Upload your ECU file — we'll identify the exact software version and confirm whether a disable is available for your car.

Upload your file