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.
Fuel Injector Circuit
Wiring diagram:
Engine Electrical System Ref. to WIRING SYSTEM>ENGINE ELECTRICAL SYSTEM>WIRING DIAGRAM
- Check or repair only faulty parts.
- Use the check board when measuring the ECM terminal voltage and resistance. Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>GENERAL DESCRIPTION>PREPARATION TOOL>HOW TO USE CHECK BOARD
- CHECK OPERATION OF EACH FUEL INJECTOR
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While cranking the engine, check each fuel injector emits operating sound. Use a sound scope or attach a screwdriver to the injector to listen to sounds for this check.
Does the fuel injector emit operating sound?
Yes : Check the fuel pressure. Ref. to MECHANICAL (H4DOTC)>FUEL PRESSURE>INSPECTION
No : Go to 2.
- CHECK HARNESS BETWEEN ECM AND FUEL INJECTOR CONNECTOR (OPEN)
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- Turn the ignition switch to OFF.
- Disconnect the connector from ECM.
- Disconnect the connector from fuel injector.
- Measure the resistance of harness between ECM and fuel injector connector.
Connector & terminal
#1 (E51) No. 15 - (E101) No. 1:
#1 (E51) No. 16 - (E101) No. 2:
#2 (E51) No. 31 - (E102) No. 1:
#2 (E51) No. 32 - (E102) No. 2:
#3 (E51) No. 47 - (E103) No. 1:
#3 (E51) No. 48 - (E103) No. 2:
#4 (E51) No. 63 - (E104) No. 1:
#4 (E51) No. 64 - (E104) No. 2:
Is the resistance less than 1 Ω?
Yes : Go to 3.
No : Repair the open circuit in harness between ECM and fuel injector connector.
- CHECK HARNESS BETWEEN ECM AND FUEL INJECTOR CONNECTOR (SHORT TO GROUND)
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Measure the resistance between fuel injector connector and engine ground.
Connector & terminal
#1 (E101) No. 1 - Engine ground:
#1 (E101) No. 2 - Engine ground:
#2 (E102) No. 1 - Engine ground:
#2 (E102) No. 2 - Engine ground:
#3 (E103) No. 1 - Engine ground:
#3 (E103) No. 2 - Engine ground:
#4 (E104) No. 1 - Engine ground:
#4 (E104) No. 2 - Engine ground:
Is the resistance 1 MΩ or more?
Yes : Go to 4.
No : Repair the short circuit to ground in harness between ECM and fuel injector connector.
- CHECK EACH FUEL INJECTOR
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Check each fuel injector. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>FUEL INJECTOR>INSPECTION
Is the check result OK?
Yes : Repair the poor contact of ECM connector.
No : Replace the faulty fuel injector. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>FUEL INJECTOR
After the faulty parts are repaired or replaced, perform the final check in Basic Diagnostic Procedure. Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>BASIC DIAGNOSTIC PROCEDURE>PROCEDURE
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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.