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DTC codes / Mercedes-Benz codes / P1335

P1335 · Mercedes-BenzCKP Sensor IFI

P1335 on Mercedes-Benz vehicles indicates that the engine control module has detected a fault in the crankshaft position sensor's interface circuit, specifically the IFI (interface) signal path. The computer monitors the CKP sensor's signal for plausibility and continuity, and it sets this code when the expected pulse pattern is missing, erratic, or electrically out of range.

SystemPowertrain
Code typeMercedes-Benz specific
SeverityMedium
Fix difficultyIntermediate
AreaIgnition system and misfire

Symptoms you may notice

  • Engine may crank but not start, or start and stall immediately
  • Intermittent stalling while driving, especially when hot or over bumps
  • Rough running or misfire due to lost synchronization
  • Tachometer may drop to zero or behave erratically
  • Often no symptoms besides the warning light if the fault is stored but not currently active

Common causes, most likely first

  1. Faulty crankshaft position sensor (CKP) internal failure
  2. Damaged or chafed wiring in the CKP interface circuit, often near the exhaust or front cover
  3. Corroded or loose connector pins at the sensor or ECM
  4. Metal debris or damage on the reluctor wheel causing signal disruption
  5. Failed or failing engine control module (ECM) driver for the CKP interface
  6. Aftermarket sensor with incorrect resistance or signal characteristics

How to diagnose and fix it

  1. Scan all modules and record freeze-frame data to confirm when P1335 sets
  2. Visually inspect the CKP sensor, connector, and harness for damage, corrosion, or oil contamination
  3. Check sensor resistance and compare to Mercedes-Benz specification; wiggle-test the harness while monitoring
  4. Use an oscilloscope to verify the CKP signal waveform at the ECM while cranking and running
  5. Check for metal shavings on the sensor tip and inspect the reluctor wheel for damage or runout
  6. If the signal is absent at the sensor but present at the ECM, repair the interface wiring or replace the ECM as needed
  7. Clear codes and perform a road test with live data to confirm the repair

CKP Interface Faults That Fool Technicians

  • A P1335 can be set by a completely dead CKP sensor, but it also appears when the sensor signal is present yet the ECM cannot interpret the interface pulses due to a bad ground or reference voltage drop.
  • On many Mercedes-Benz engines, the CKP sensor shares a ground or shield with other sensors, so a fault in a neighbouring circuit can corrupt the CKP interface and set P1335 without any problem in the sensor itself.
  • Technicians often replace the CKP sensor only to find the code returns because the reluctor wheel has a cracked or missing tooth that disrupts the signal at a specific crankshaft angle.
  • A weak battery or poor engine ground can cause the ECM to log P1335 during cranking because the interface circuit cannot maintain a stable reference voltage, so always check charging and grounds before condemning parts.
  • Aftermarket CKP sensors for Mercedes-Benz are a common source of repeat P1335 codes because their internal interface electronics do not match the OEM signal timing, even though they fit and produce a waveform.

Can I keep driving with P1335?

If the engine starts and runs normally, you can drive cautiously to a workshop, but avoid long trips and high-speed driving because a sudden stall is possible. If the engine cranks without starting or stalls repeatedly, do not drive; have the vehicle towed for diagnosis.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for Mercedes-Benz vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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