GM Duramax · Crankshaft Position Sensor CircuitHigh

GM Duramax P0335: Crankshaft Position Sensor Malfunction

P-Code P0335 (FMI N/A) — Crankshaft Position Sensor "A" Circuit Malfunction

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Quick Answer

P0335 means the GM Duramax PCM isn't receiving a usable crankshaft position signal. It's a High severity fault that can cause hard starting, stalling, or in severe cases, a complete no-start condition.

Overview: GM Duramax P-Code P0335

The crankshaft position sensor is one of the most critical inputs on any Duramax engine, since the PCM needs it to know exactly where each piston is for correct injection timing. P0335 flags a total signal loss rather than an erratic reading, which is why symptoms tend to be more severe than a simple rough idle. ProfessionalDieselRepair.com always recommends starting with the connector and harness inspection since corrosion and chafing account for most of these faults.

Repair Snapshot

Time

1 - 2.5 Hours

Difficulty

Intermediate

Parts Cost

$70 - $220

Dealer Labor

$350+

Tools Required

  • GM Tech2Win/GDS2
  • Multimeter
  • Snap-on NEXIQ
  • Diesel Laptops Diagnostic Software

What P-Code P0335 Means

P0335 means the PCM isn't receiving a usable signal from the crankshaft position sensor, which it depends on for both injection timing and basic engine operation. Depending on how completely the signal is lost, symptoms range from a rough-running engine to a complete stall or no-start. The MIL illuminates and this fault should be treated as a priority since a total signal loss can leave you stranded.

Symptoms Drivers Notice

  • Hard starting or extended cranking
  • MIL illuminated
  • Possible stalling while driving
  • Complete no-start condition in severe cases

Most Likely Root Causes

Corroded or water-intruded sensor connector

Common

The connector's location low on the engine block makes it vulnerable to moisture and road spray, leading to corrosion over time.

Chafed sensor harness near the front of the engine

Common

Engine vibration wears through wire insulation where the harness runs close to accessory drive components, eventually breaking the conductor.

Failed crankshaft position sensor

Occasional

The sensor's internal Hall-effect element can fail from heat and vibration fatigue over extended service life.

PCM internal fault on that specific input

Rare

An internal PCM issue on that circuit would produce the same code, but only after the sensor and harness both test clean.

Common Misdiagnoses (Don't Waste Parts)

Replacing the sensor without checking the connector for corrosion

Why it happens: It's a parts-cannon shortcut that skips the simple, often effective connector cleaning step.

Do this instead: Inspect and clean the connector first, since corrosion here is a very common and inexpensive fix compared to a sensor replacement.

Chasing a fuel delivery problem for hard starting symptoms

Why it happens: Hard starting looks like an air-in-fuel-system or fuel filter issue at first glance.

Do this instead: Always pull codes before assuming a fuel problem - a crankshaft sensor fault produces identical cranking symptoms without any fuel system involvement.

Overlooking a correlation fault with the camshaft sensor

Why it happens: Techs focus only on the named crankshaft sensor code and miss the bigger picture of a shared harness routing issue.

Do this instead: Check for accompanying camshaft position codes, since a correlation mismatch can point to either sensor or a shared wiring problem.

Master Tech Commentary

Mechanic's Notes

Shop tip from ProfessionalDieselRepair.com: check the connector for corrosion and confirm the sensor is fully seated before ordering a replacement. A sensor that's not pushed in all the way after a previous repair reads exactly like a failed sensor on this code.

Step-by-Step Diagnostic Procedure

  1. Step 1: Scan for codes with GM Tech2Win/GDS2 or a comparable tool and check freeze-frame data for engine temperature and RPM when the fault occurred.
  2. Step 2: Inspect the crankshaft position sensor connector for corrosion, damage, or a loose fit at its mounting location on the engine block.
  3. Step 3: Unplug the sensor and measure resistance across its terminals with a multimeter, comparing to the Duramax spec for your engine.
  4. Step 4: Trace the sensor harness back toward the PCM, checking for chafing near the front of the engine or accessory drive bracket.
  5. Step 5: Replace the sensor or repair the harness as needed, clear the code, and verify normal starting and running behavior across multiple key cycles.

Live Data & Freeze-Frame Tips

With your scan tool connected, monitor crankshaft position sensor status while cranking - a completely flat or missing signal confirms a total loss condition consistent with P0335, which helps rule out a simple erratic-signal fault that would present differently.

Safety Warnings

  • Never work near the front of the engine or accessory drive with the engine running.
  • Allow the engine to cool before accessing sensors near the engine block.
  • Disconnect the batteries before removing or adjusting the crankshaft sensor.
  • Keep loose clothing and tools clear of rotating components during inspection.

When to Limp In vs Tow

If the truck experiences a complete no-start condition, towing to a repair facility is the safer option rather than repeated cranking attempts, which can drain the battery and potentially damage the starter.

Prevention Tips for Fleets & Owner-Operators

  • Inspect the crankshaft sensor connector for corrosion at every major PM interval.
  • Apply dielectric grease to the connector when reassembling after any front engine service.
  • Route the sensor harness away from vibration-prone brackets during any front engine work.
  • Replace aging sensors proactively on high-mileage trucks showing early signs of intermittent hard starting.

Related Fault Codes

P0336

Crankshaft position sensor circuit range/performance, a related but less severe version of the same sensor fault.

P0340

Camshaft position sensor circuit malfunction, the companion timing sensor the PCM cross-checks against this one.

P0016

Crankshaft/camshaft position correlation fault, worth checking if both timing sensors show related issues.

Frequently Asked Questions

Can I drive with P0335 active?

You can drive if the engine is still running normally, but there's a real risk of a stall or a no-start on the next attempt, so prompt diagnosis is recommended.

How do I reset this code without a scanner?

A battery disconnect may temporarily clear the stored fault, but it will return as soon as the signal loss condition reoccurs if the underlying wiring or sensor issue isn't repaired.

Does this cause an emissions-style derate?

No, this isn't an emissions inducement fault - the main risk is stalling or a no-start condition rather than a gradual power derate.

Why won't my truck start at all with this code?

If the crankshaft signal is completely absent, the PCM can't confirm engine position well enough to safely start or run the engine, resulting in extended cranking or a complete no-start.

Is the crankshaft sensor expensive to replace?

No, the sensor itself is typically inexpensive, usually under $150, though labor cost depends on how accessible it is on your specific engine.

Can water cause this code?

Yes, water intrusion at the connector is a common cause, especially on trucks that are frequently driven through deep water or pressure washed around the engine bay.