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.
Ignition Coil Relay Circuit Troubleshooting
- Check the No. 2 (15 A) fuse in the driver's under-hood fuse/relay box.
Is the fuse OK?
YES -Reinstall the fuse, then go to step 2.
NO -Replace the fuse. If the fuse continues to blow, locate and repair the short in the circuit between the under-hood fuse/relay box and the ignition coils.?
- Remove the ignition coil relay from the driver's under-hood fuse/relay box, and test it.
Is the relay OK?
YES -Go to step 3.
NO -Replace the ignition coil relay.?
- Measure the voltage between ignition coil relay 4P socket terminal No. 1 and body ground, then terminal No. 4 and body ground.
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Is there battery voltage?
YES -Go to step 4.
NO -Replace the driver's under-hood fuse/relay box.?
- Check for continuity between each ignition coil relay 4P socket terminal No. 2 and ignition coil 3P connector terminal No. 3.
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Is there continuity?
YES -Go to step 5.
NO -Repair open in the wire between ignition coil relay 4P socket terminal No. 2 and ignition coil 3P connector terminal No. 3.?
- Check for continuity between each ignition coil 3P connector terminal No. 2 and the body ground.
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Is there continuity?
YES -Go to step 6.
NO -Repair open in the wire between ignition coil 3P connector terminal No. 2 and the body ground.?
- Connect the Honda Diagnostic System (HDS) to the data link connector (DLC) (see HOW TO USE THE HDS (HONDA DIAGNOSTIC SYSTEM) ).
- Turn the ignition switch to ON (II).
- Make sure the HDS communicates with the vehicle and the powertrain control module (PCM). If it does not communicate, troubleshoot the DLC circuit.
- Jump the SCS line with the HDS, then turn the ignition switch to LOCK (0).NOTE: This step must be done to protect the PCM from damage.
- Disconnect PCM connector A (49P).
- Check for continuity between ignition coil relay 4P socket terminal No. 3 and body ground.
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Is there continuity?
YES -Repair short in the wire between ignition coil relay 4P socket terminal No. 3 and the PCM connector terminal A6.
NO -Go to step 12.
- Check for continuity between ignition coil relay 4P socket terminal No. 3 and PCM connector terminal A6.Fig 5: Checking Continuity Between Ignition Coil Relay 4P Socket Terminal No. 3 And PCM Connector Terminal A6.
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Is there continuity?
YES -The system is OK at this time. Check for loose or poor connections at the ignition coil relay and the PCM connector terminal A6.
NO -Repair open in the wire between ignition coil relay 4P socket terminal No. 3 and PCM connector terminal A6.
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.