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 MANUALSMITSUBISHI2004ECLIPSE L4-2.4L SOHCREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTIGNITION SYSTEMIGNITION COILTESTING AND INSPECTIONOSCILLOSCOPE CHECK
2004 Mitsubishi Eclipse L4-2.4L SOHC
Oscilloscope Check
2004 Mitsubishi Eclipse L4-2.4L SOHCSECTION Oscilloscope Check
IGNITION COIL AND IGNITION POWER TRANSISTOR
Required Special Tool:
- MB991348: Test Harness Set
Measurement Method
1. Disconnect the ignition coil connector, and connect test harness special tool, MB991348, in between. (All terminals should be connected.)
2. Connect the oscilloscope probe to ignition coil connector terminal No. 3.
Alternate method (Test harness not available)
Connect the oscilloscope probe to ECM terminal No. 10 (for number 1 - number 4), terminal No. 23 (for number 2 - number 3) respectively.
Connect the oscilloscope probe to PCM terminals No. 11 (for number 1 - number 4), terminal No. 12 (for number 2 - number 3) respectively.
Standard Wave Pattern
Wave Pattern Observation Points
Point: Condition of wave pattern build-up section and maximum voltage (Refer to abnormal wave pattern examples 1 and 2).
Examples of Abnormal Wave Patterns
Example 1 (Wave pattern during engine cranking)
- Cause of problem
Open-circuit in ignition primary circuit
- Wave pattern characteristics
Top-right part of the build-up section cannot be seen, and voltage value is approximately 2 volts too low.
Example 2 (Wave pattern during engine cranking)
- Cause of problem
Malfunction in ignition power transistor
- Wave pattern characteristics
Power voltage results when the ignition power transistor is ON.
Required Special Tool:
- MB991348: Test Harness Set
Measurement Method
1. Disconnect the ignition coil connector, and connect test harness special tool, MB991348, in between. (All terminals should be connected.)
2. Connect the oscilloscope probe to ignition coil connector terminal No. 3.
Alternate method (Test harness not available)
Connect the oscilloscope probe to ECM terminal No. 10 (for number 1 - number 4), terminal No. 23 (for number 2 - number 3) respectively.
Connect the oscilloscope probe to PCM terminals No. 11 (for number 1 - number 4), terminal No. 12 (for number 2 - number 3) respectively.
Standard Wave Pattern
Wave Pattern Observation Points
Point: Condition of wave pattern build-up section and maximum voltage (Refer to abnormal wave pattern examples 1 and 2).
Examples of Abnormal Wave Patterns
Example 1 (Wave pattern during engine cranking)
- Cause of problem
Open-circuit in ignition primary circuit
- Wave pattern characteristics
Top-right part of the build-up section cannot be seen, and voltage value is approximately 2 volts too low.
Example 2 (Wave pattern during engine cranking)
- Cause of problem
Malfunction in ignition power transistor
- Wave pattern characteristics
Power voltage results when the ignition power transistor is ON.
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.