Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSMITSUBISHI2009LANCER L4-2.4L (4B12)REPAIR AND DIAGNOSISSTARTING AND CHARGINGCHARGING SYSTEMTESTING AND INSPECTIONOSCILLOSCOPE PATTERNS AND WAVEFORMS
2009 Mitsubishi Lancer L4-2.4L (4B12)
Oscilloscope Patterns and Waveforms
2009 Mitsubishi Lancer L4-2.4L (4B12)SECTION Oscilloscope Patterns and Waveforms
WAVE PATTERN CHECK USING AN OSCILLOSCOPE
MEASUREMENT METHOD
Connect the oscilloscope special patterns pick-up to the generator "B" terminal.
Standard Waveform
NOTE: The voltage waveform of the generator "B" terminal can undulate as shown at left. This waveform is produced when the regulator operates according to fluctuations in the generator load (current), and is normal for the generator.
If the ripple height is abnormally high (approximately 2 V or more during idling), the wires between the generator "B" terminal and the battery have broken due to fuse blowing, etc. The generator is usually operating properly.
ABNORMAL WAVEFORMS EXAMPLES
NOTE:
- The size of the waveform patterns can differ greatly, depending on the adjustment of the variable knob on the oscilloscope.
- Identification of abnormal waveforms is easier when there is a large output current (regulator is not operating). (Waveforms can be observed when the headlights are illuminated.)
- Check the conditions of the generator malfunction light (illuminated/not illuminated) also, and carry out a total check.
ABNORMAL WAVEFORMS [Non-turbo]
- Example 1
PROBABLE CAUSE: Open circuit in diode
- Example 2
PROBABLE CAUSE: Short-circuit in diode
- Example 3
PROBABLE CAUSE: Open circuit in stator coil
- Example 4
PROBABLE CAUSE: Short-circuit in stator coil
ABNORMAL WAVEFORMS [Turbo]
- Example 1
PROBABLE CAUSE: Open circuit or short circuit in diode
- Example 2
PROBABLE CAUSE: Open circuit in stator coil (In stator coil)
- Example 3
PROBABLE CAUSE: Open circuit in stator coil (Open circuit between stator coil and diode)
- Example 4
PROBABLE CAUSE: Short circuit in stator coil
MEASUREMENT METHOD
Connect the oscilloscope special patterns pick-up to the generator "B" terminal.
Standard Waveform
NOTE: The voltage waveform of the generator "B" terminal can undulate as shown at left. This waveform is produced when the regulator operates according to fluctuations in the generator load (current), and is normal for the generator.
If the ripple height is abnormally high (approximately 2 V or more during idling), the wires between the generator "B" terminal and the battery have broken due to fuse blowing, etc. The generator is usually operating properly.
ABNORMAL WAVEFORMS EXAMPLES
NOTE:
- The size of the waveform patterns can differ greatly, depending on the adjustment of the variable knob on the oscilloscope.
- Identification of abnormal waveforms is easier when there is a large output current (regulator is not operating). (Waveforms can be observed when the headlights are illuminated.)
- Check the conditions of the generator malfunction light (illuminated/not illuminated) also, and carry out a total check.
ABNORMAL WAVEFORMS [Non-turbo]
- Example 1
PROBABLE CAUSE: Open circuit in diode
- Example 2
PROBABLE CAUSE: Short-circuit in diode
- Example 3
PROBABLE CAUSE: Open circuit in stator coil
- Example 4
PROBABLE CAUSE: Short-circuit in stator coil
ABNORMAL WAVEFORMS [Turbo]
- Example 1
PROBABLE CAUSE: Open circuit or short circuit in diode
- Example 2
PROBABLE CAUSE: Open circuit in stator coil (In stator coil)
- Example 3
PROBABLE CAUSE: Open circuit in stator coil (Open circuit between stator coil and diode)
- Example 4
PROBABLE CAUSE: Short circuit in stator coil
RENDER: 1.0x
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.