Engine position / CKP

CRANKSHAFT POSITION SENSOR

Tracks crankshaft speed and angular position. Common designs are two-wire variable-reluctance sensors and three-wire Hall-effect sensors.

FIELD GUIDE01/13

Identify the circuit first

ONE NAME.
DIFFERENT SIGNALS.

Pin count is a clue, not proof. Confirm the exact architecture before resistance testing, applying voltage or judging the waveform.

TYPE 01ACTIVE / DIGITAL

Hall-Effect CKP

Usually 3 wires: supply, ground and signal

Requires an external supply and produces a switched square wave, often even at very low cranking speed.

Reading the signal

Good waveform

Logic levels and edge transitions are consistent with the installed circuit. Pulse timing changes in the specified way as the input changes; intended index gaps or encoded features repeat correctly.

Faulty waveform

Missing or extra edges, weak switching levels, intermittent pulse loss or a stuck level can indicate supply, ground, wiring, target or sensor problems. A steady level can be normal when the target is stationary. Decode encoded signals using the correct protocol.

TYPE-SPECIFIC TESTS

+ Verify the specified supply and loaded ground first.

+ Back-probe the signal during crank; confirm it switches near both logic levels.

+ Check the missing-tooth or index window and compare timing to CMP.

EXPECTED

✓ Consistent high/low levels

✓ Clean edges at low speed

✓ Repeatable sync gap

COMMON FAULTS

— Signal stuck high/low

— Missing supply or ground

— Dropout from excessive air gap

TYPE 02PASSIVE / ANALOG

Variable-Reluctance CKP

Usually 2 wires, often shielded

Generates its own AC voltage as a ferrous tooth changes magnetic flux. Amplitude grows with speed.

Reading the signal

Good waveform

A passive variable-reluctance pickup produces an alternating signal as the target moves. Amplitude generally increases with speed, and tooth spacing or index features repeat consistently at a steady speed.

Faulty waveform

Weak output during cranking, recurring distorted teeth or random dropouts can arise from excessive air gap, target damage, wiring or the pickup. Compare at the same speed and polarity; a low-speed trace should not be judged against a high-speed amplitude.

TYPE-SPECIFIC TESTS

+ Confirm sensor resistance only when an OEM specification is available.

+ Scope across both sensor wires while cranking.

+ Compare positive/negative amplitude, tooth spacing and sync gap.

EXPECTED

✓ AC waveform centered around zero

✓ Amplitude rises with speed

✓ Even tooth peaks and repeatable gap

COMMON FAULTS

— Weak amplitude from air gap

— Shorted turns

— Damaged reluctor tooth or shield

Correct theory and operation

HOW IT
WORKS.

Understand the component, its circuit and the controller's strategy before interpreting the waveform or beginning disassembly.

01

Sensing principle

Tracks crankshaft speed and angular position. Common designs are two-wire variable-reluctance sensors and three-wire Hall-effect sensors.

02

Circuit architecture

A variable-reluctance sensor generates its own AC voltage as reluctor teeth change magnetic flux. A Hall or magnetoresistive sensor instead requires power and ground and switches an electronic output.

03

Controller interpretation

The controller counts edges to calculate speed and uses the missing-tooth or index feature as an angular reference. CKP is the primary timing input for spark and injection; CMP identifies engine phase.

04

Normal response

Hall: clean digital switching between low and high states. Variable reluctance: even AC sine pattern that grows with speed. Missing-tooth gap must repeat consistently without extra dropouts.

05

System relationship

Judge the signal only under a defined operating condition. Verify its power, reference, ground, mechanical input and related scan data before deciding the sensing element is incorrect.

Common mistakes

AVOID THE
FALSE CLUE.

COMPLETE TEST SEQUENCE

  1. Identify Hall or variable-reluctance design from service information before testing.
  2. Inspect the sensor face, air gap, connector and trigger wheel for damage or debris.
  3. Verify power and ground on an active Hall sensor; do not resistance-test an unidentified sensor.
  4. Back-probe the signal while cranking, then compare amplitude, spacing and the missing-tooth reference.
DO NOT CONDEMN A SENSOR

until its power, ground, signal circuit, mechanical target and related system inputs have been verified.

NEXT GUIDE / CMPCamshaft Position Sensor→

Diagnostic details

Purpose

CKP information allows the ECM to determine crankshaft speed and position for ignition, fuel injection, synchronization and misfire detection.

Scan tool data

  • Engine RPM during cranking
  • CKP-related DTCs
  • Cam/crank synchronization
  • Misfire data

Failure symptoms

  • No-start
  • Intermittent stall
  • Extended cranking
  • Loss of RPM signal

Related DTCs

  • P0335 – CKP Sensor A Circuit
  • P0336 – CKP Range/Performance
  • P0337 – CKP Circuit Low
  • P0338 – CKP Circuit High
  • P0339 – CKP Circuit Intermittent

Diagnostic tips

  • Check scan-tool RPM during cranking.
  • A CKP DTC does not automatically prove the sensor failed.
  • Inspect the trigger wheel and sensor mounting.
  • Compare CKP and CMP when diagnosing correlation problems.

Construction & type-specific testing

Identify the installed design before testing. Construction, signal format and redundant channels are separate attributes; use only the procedure for the actual component.

Hall Effect

Powered sensor producing a digital position signal.

Operating principle

  • A magnetic field interacts with a Hall element.
  • A rotating target changes the magnetic field.
  • Electronics switch the output between defined voltage states.

Circuit identification

Typically 3 wires

Wiring

  • Power/reference

Expected readings

  • Supply voltage depends on vehicle design.
  • Signal switches between defined high and low voltage states.

Multimeter testing

  • Verify sensor power.
  • Verify sensor ground.
  • Check for signal switching.
  • A meter may not reveal short-duration signal faults.

Oscilloscope setup

  • DC coupling
  • Connect to the CKP signal
  • Set voltage scale to display signal high and low states
  • Use edge triggering for a stable display

Oscilloscope testing

  • Look for clean digital transitions.
  • Check pulse spacing.
  • Look for missing pulses.
  • Look for intermittent dropouts.

Waveform interpretation

Typical digital Hall-effect crankshaft position waveform.

Common failures

  • Loss of sensor power
  • Poor ground
  • Signal circuit fault
  • Internal sensor failure
  • Damaged trigger wheel

Diagnostic tips

  • Do not resistance-test a Hall sensor as though it were a passive VR sensor.
Variable Reluctance

Passive magnetic sensor producing an AC waveform.

Operating principle

  • A permanent magnet and coil form the sensor.
  • Reluctor teeth passing the sensor change magnetic flux.
  • The changing magnetic field induces AC voltage.
  • Signal amplitude increases with rotational speed.

Circuit identification

Typically 2 wires

Wiring

  • Signal positive
  • Signal negative
  • Shielding may be used

Expected readings

  • Produces an AC waveform while the target rotates.
  • Amplitude is speed-dependent.
  • Exact minimum cranking amplitude is vehicle-specific.

Multimeter testing

  • Resistance may be checked when the manufacturer provides a specification.
  • AC voltage may be checked during cranking when appropriate.
  • A resistance test alone does not prove dynamic sensor operation.

Oscilloscope setup

  • AC coupling can be useful for waveform inspection.
  • Connect across the sensor signal circuits.
  • Set the voltage range for cranking amplitude.
  • Use a time base that displays multiple reluctor teeth.

Oscilloscope testing

  • Look for a consistent AC waveform.
  • Check amplitude.
  • Look for missing or distorted pulses.
  • Observe the missing-tooth synchronization pattern when applicable.

Waveform interpretation

Typical variable-reluctance CKP sine-like waveform with a synchronization feature.

Common failures

  • Open sensor winding
  • Shorted winding
  • Metal debris on sensor

Diagnostic tips

  • Low cranking speed can reduce signal amplitude.
  • Sensor air gap matters on many VR systems.