Optical CranKshaft Position (CKP) Sensor
• Theory of Operation
These CKP sensors are classified as “CKP Sensors - High Resolution” in industry.
The optical CKP sensors can sense position of a rotating component even without the engine running and t heir
pulse amplitude remains constant with variations in speed. They are not affected by electromagnetic interference
(EMI). They are used to switch the ignition and/or fuel injection triggering circuits on and off.
The optical sensor consists of a rotating disk with slots in it, two fiber optic light pipes, an LED, and a phototransistor
as the light sensor. An amplifier is coupled to the phototransistor to create a strong enough signal for use by other
electronic devices, such as PCM or ignition module.
The phototransistor and amplifier create a digital output signal (on/off pulse).
• Symptoms [OBD II DTC’s: P0340 ~ P0349, P0365 ~ P0369, P0390 ~ P0394]
No or hard starts, stall at stops, misfires, poor fuel economy, emissions failure
• Test Procedure
1. Connect the CH A lead to the sensor output or HI and its ground lead to the sensor output LO or GND.
2. With K OE R (Key On, Engine Running), let t he engine idle, or use the thrott le to accelerate or decelerate the
engine or drive the vehicle as needed to make the driveability, or emissions, problem occur.
3. Use the Glitch Snare mode to catch dropouts or stabilize waveforms when a “sync” pulse is created.
• Reference Waveform
VEHICLE INFORMATION
YEAR
: 1989
MAKE
: Mitsubishi
MODEL
: Montero
ENGINE
: 3.0 L
FUELSYS : Multiport Fuel Injection
PCM_PIN : 22 Blk wire at PCM
STATUS
: KOER (Key On Running)
RPM
: Idle
ENG_TMP : Operating Temperature
VACUUM : 20 In. Hg
MILEAGE : 184066
6-15
The amplitude, frequency, and shape should be all consistent in the waveform from
pulse to pulse. The amplitude should be sufficient, the time between pulses repeatable
(except for “sync” pulses), and the shapes repeatable and predictable. Consistency is
the key.
FREQ = 2.27 kHz
MAX = 5.06 V
MIN = -133 mV
Frequency Modulated signal.
Frequency increases with
increasing engine RPM. Duty
cycle stays constant.
• Symptoms [OBD II DTC’s: P0340 ~ P0349, P0365 ~ P0369, P0390 ~ P0394]
Long cranking, poor fuel economy, emissions problem
• Test Procedure
1. Connect the CH A lead to the sensor output or HI and its ground lead to the sensor output LO or GND.
2. With KOEC (Key On, Engine Cranking), or with KOER, use the throttle to accelerate or decelerate the engine or
drive the vehicle as needed to make the driveability, or emissions, problem occur.
3. Use the Glitch Snare mode to catch dropouts or stabilize waveforms when a “sync” pulse is created.
• Reference Waveform
VEHICLE INFORMATION
YEAR
: 1985
MAKE
: Volkswagen
MODEL
: Jetta
ENGINE
: 1.8 L
FUELSYS : CIS Fuel Injection
PCM_PIN : 9 GryWht wire
STATUS
: KOEC (Key On Cranking)
RPM
: Cranking
ENG_TMP : Operating Temperature
VACUUM : 5 In. Hg
MILEAGE : 105522
• Troubleshooting Tips
The duty cycle of the waveform changes only when a “sync” pulse is displayed. Any other changes in duty cycle can
mean troubles.
The top and bottom corners of the waveform should be sharp and voltage transitions of the edge should be straight
and vertical.
Make sure the waveform isn’t riding too high off the ground level. This could indicate a high resistance or bad ground
supply to the sensor.
Although the Hall CKP sensors are generally designed to operate in temperatures up to 318 °F (150 °C), they can
fail at certain temperatures (cold or hot).
6-14
The amplitude, frequency, and shape should be all consistent in the waveform from
pulse to pulse. The amplit ude should be sufficient (usually equal to sensor supply
volt age), t he time between pulses repeat able (except f or “sync” pulses), and the
shapes repeatable and predictable. Consistency is the key.
FREQ = 11.3 Hz
MAX = 8.33 V
MIN = 0.00 V
Cranking test of Hall type (in dist.)
crankshaft position (CKP) sensor
