Ram Cummins · Crankshaft Position SensorHigh

Ram Cummins P0335: Crankshaft Position Sensor A Circuit Malfunction

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

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Quick Answer

P0335 on a Ram Cummins means the ECM received no usable crankshaft position signal. The truck typically will not start or stalls and won't restart. Check the sensor connector for corrosion, verify the air gap, and test the sensor output before replacing anything — wiring and connector issues cause this more often than sensor failure.

Overview: Ram Cummins P-Code P0335

P0335 on a Ram 2500 or 3500 Cummins tends to show up as a no-start that looks completely mysterious — the engine cranks fine, fuel pressure is up, and there is no smoke, but it simply will not fire. The reason is straightforward: without a crankshaft position signal, the ECM cannot synchronize injection timing and will not deliver fuel. ProfessionalDieselRepair.com sees this most often as a connector corrosion issue at the CKP sensor rather than a failed sensor itself. Pull the connector, clean the terminals, and verify the air gap before reaching for a new sensor.

Repair Snapshot

Time

1–3 hours

Difficulty

Moderate

Parts Cost

$30–$120 for CKP sensor

Dealer Labor

$150–$400

Tools Required

  • Cummins INSITE
  • Snap-on NEXIQ
  • Multimeter
  • Feeler gauges for air gap check

What P-Code P0335 Means

P0335 on the Ram Cummins means the ECM received no usable signal from the crankshaft position sensor (CKP). The 6.7L Cummins relies on the CKP to establish engine timing and synchronize fuel injection — without it, the engine will typically not start or will stall and not restart. This is a hard electrical fault (complete signal loss) distinct from P0336, which flags a noisy or intermittent signal. Diagnose the sensor, its air gap, and the wiring harness before assuming anything internal to the ECM.

Symptoms Drivers Notice

  • No-start condition — engine cranks but will not fire
  • Engine stalls while running and will not restart
  • MIL illuminated, often alongside camshaft sensor codes (P0340)
  • Tachometer reading zero while cranking
  • Extended cranking before start on warm restarts if the fault is intermittent

Most Likely Root Causes

Corroded or damaged sensor connector

High

The CKP connector on the 6.7L Cummins is exposed to engine bay heat, oil mist, and moisture. Terminal corrosion causes a high-resistance open that kills the signal completely while the sensor itself is still functional.

Failed crankshaft position sensor

Moderate

The sensor's internal magnet or winding can fail outright, especially on higher-mileage engines. A failed sensor produces zero AC output during cranking and must be replaced.

Excessive air gap between sensor and reluctor ring

Moderate

If the sensor mounting bolt loosens over time or the sensor was not fully seated at a prior service, the gap between the sensor tip and the reluctor ring grows beyond specification. The signal becomes too weak to register and P0335 sets.

Damaged reluctor ring

Low

A cracked, chipped, or missing tooth on the crankshaft reluctor ring produces a hard fault at that specific crank angle. The ECM sees a gap in the position signal it cannot correlate and sets P0335.

Common Misdiagnoses (Don't Waste Parts)

Replacing the ECM as a parts-cannon approach when the sensor and wiring were never properly tested

Why it happens: A P0335 no-start with a known-good fuel system and good battery leads some technicians to assume the ECM has failed since everything else appears fine.

Do this instead: Test the CKP sensor output with a multimeter during cranking. Verify wiring continuity from sensor to ECM. Inspect the connector thoroughly. The ECM is almost never the cause of P0335 on the 6.7L Cummins.

Replacing the camshaft position sensor first when P0335 and P0340 are stored together

Why it happens: Both crank and cam sensor codes appearing together suggests both sensors failed simultaneously, which is unusual. Technicians sometimes replace the cam sensor first since it is cheaper and easier to access.

Do this instead: P0335 and P0340 co-occurring often points to a shared power or ground circuit issue, or a timing/gear problem rather than two separate sensor failures. Diagnose power supply and grounds to both sensors before replacing either.

Overlooking the air gap after reinstalling a sensor at a prior service

Why it happens: If the front cover was off for timing gear work or a front main seal replacement, the CKP sensor may have been reinstalled without verifying the air gap specification.

Do this instead: After any front cover work, always verify the CKP air gap with feeler gauges before buttoning everything up. Takes 2 minutes and prevents a callback.

Master Tech Commentary

Mechanic's Notes

P0335 on the 6.7L Cummins is almost always a sensor, gap, or connector issue — not an ECM failure. ProfessionalDieselRepair.com has seen shops replace ECMs chasing this code when the real culprit was a corroded two-pin connector that cost $8 to replace. Inspect the connector first and clean the terminals with contact cleaner before touching anything else. The front cover mounting location on the 6.7L exposes the sensor to oil mist and heat cycling, which accelerates connector terminal corrosion over time. Also check the reluctor ring carefully — a cracked or partially delaminated ring tooth produces a hard no-signal fault at the specific crank angle where the damaged tooth passes, and that can be mistaken for a completely dead sensor.

Step-by-Step Diagnostic Procedure

  1. Step 1: 1. Connect Cummins INSITE or Snap-on NEXIQ and confirm P0335 is stored. Note any co-codes — a simultaneous P0340 (cam sensor) points to possible timing issues or a shared power/ground failure rather than just the CKP.
  2. Step 2: 2. Locate the crankshaft position sensor on the 6.7L Cummins — it is typically mounted on the front gear cover near the crankshaft reluctor ring.
  3. Step 3: 3. Inspect the connector for corrosion, pushed-back terminals, or damaged lock tabs. A corroded connector on a magnetic sensor causes exactly this fault. Clean and reseat before condemning the sensor.
  4. Step 4: 4. Check the sensor mounting bolt is fully torqued. A loose sensor that has backed out even slightly creates too large an air gap for the reluctor ring signal to register.
  5. Step 5: 5. Check the air gap between the sensor tip and the reluctor ring. Refer to the Cummins specification — on the 6.7L it is typically 0.020–0.080 inches. Too large = no signal.
  6. Step 6: 6. Inspect the reluctor ring on the crankshaft for cracked, chipped, or missing teeth. Crank the engine by hand and watch each tooth pass the sensor.
  7. Step 7: 7. With a multimeter on AC millivolts, measure the sensor output signal during cranking by backprobing the signal wire at the connector. No AC voltage during cranking with a good gap confirms a dead sensor.
  8. Step 8: 8. Check wiring from the sensor to the ECM for an open circuit — especially at any flex points near the front cover.

Professional service / OEM-level scan tools are recommended before clearing this fault for good.

Live Data & Freeze-Frame Tips

With Cummins INSITE or Snap-on NEXIQ, watch the Engine Speed PID during a crank attempt. If RPM reads zero during cranking with a fully charged battery, the ECM is not receiving the CKP signal. Also check for Cam/Crank Synchronization status — INSITE on the 6.7L Cummins will show a synchronization fault flag that helps confirm the CKP as the cause rather than an electrical system issue masking itself as a no-start.

Safety Warnings

  • If the engine stalls at highway speed due to an intermittent P0335, power steering and brake boost will be reduced. Pull to the side of the road safely and do not attempt to restart until diagnosed.
  • Do not crank the engine excessively trying to force a start with P0335 active — extended cranking without ignition can fill the cylinders with raw fuel and cause hydrolock on restart.

When to Limp In vs Tow

Tow if the truck will not start. An intermittent P0335 that allows starting should be diagnosed before any long trip — the fault will eventually leave the truck stranded, and diesel breakdown on a highway shoulder is a dangerous situation.

Prevention Tips for Fleets & Owner-Operators

  • Apply dielectric grease to the CKP connector at every timing or front cover service.
  • Verify the CKP air gap to spec any time the front cover or timing components are serviced.
  • Inspect the CKP wiring harness routing for chafe points at the front of the engine annually.

Related Fault Codes

P0336

CKP range/performance — signal is present but noisy or out of correlation

P0340

Cam position sensor malfunction — often co-occurs with P0335 when a shared circuit is at fault

P0344

Cam position sensor intermittent — related cam signal fault that can accompany CKP issues

Frequently Asked Questions

Why won't my Ram Cummins start with P0335?

Without a crankshaft position signal, the ECM cannot calculate injection timing and will not fire the injectors. The engine cranks but gets no fuel delivery. Fix the CKP signal and the no-start condition resolves.

Can P0335 on a Ram Cummins cause a stall while driving?

Yes. If the fault is intermittent — a loose connector or a sensor that loses signal under heat — the engine can stall at any speed. It typically will not restart until the engine cools and the intermittent fault temporarily resolves.

How do I test the crankshaft position sensor with a multimeter?

Set to AC millivolts. Backprobe the signal and ground terminals at the sensor connector with the connector plugged in. Have someone crank the engine. A working passive CKP sensor should produce oscillating AC voltage during cranking. Zero output confirms a dead sensor or open wiring.

Could a bad timing gear cause P0335?

Yes. If a timing gear is cracked or has damaged teeth, the reluctor ring on the crank can exhibit signal gaps. This is uncommon but does happen on higher-mileage engines. It shows up as P0335 with no wiring or sensor fault found.

What is the air gap specification for the CKP sensor on the 6.7L Cummins?

The general specification is approximately 0.020 to 0.080 inches between the sensor tip and the reluctor ring. Always verify against the current Cummins service manual for your specific engine build — the spec can vary slightly by model year.

How much does a CKP sensor replacement cost on a Ram Cummins?

The sensor itself is $30–$120 depending on brand. Labor at a diesel shop runs $150–$400 depending on access. If the connector is the actual fault, terminal repair kits run $10–$25 and save the sensor replacement entirely.