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 under-dash 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-dash fuse/reley box and the ignition coils.
- Remove the ignition coil relay from the under-dash fuse/relay box, and test it (see
POWER RELAY TEST
).
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 the body ground.
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Is there battery voltage?
YES - Go to step 4.
NO - Repair open in the wire between under-hood fuse/relay box and ignition coil relay.
- Check for continuity between ignition coil relay 4P socket terminal No. 2 and the each ignition coil 3P connector terminal No. 3.Fig 2: Checking Continuity Between 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 each 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 ON (II).
- '07-08 models: Make sure the HDS communicates with the vehicle and the engine control module (ECM)/powertrain control module (PCM). If it doesn't communicate, troubleshoot the DLC circuit (see '07-08 MODELS ).
- Jump the SCS line with the HDS, then turn the ignition switch OFF.NOTE: This step must be done to protect the ECM/PCM from damage.
- Disconnect ECM/PCM connector E (31P).
- Check for continuity between ignition coil relay 4P socket terminal No. 3 and the 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 ECM/PCM (E7).
NO - Go to step 12.
- Check for continuity between ignition coil relay 4P socket terminal No. 3 and the ECM/PCM connector terminal E7.Fig 5: Checking Continuity Between Ignition Coil Relay 4P Socket Terminal No. 3 And ECM/PCM Connector Terminal E7
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 ECM/PCM (E7).
NO - Repair open in the wire between ignition coil relay 4P socket terminal No. 3 and the ECM/PCM (E7).
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.