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 MANUALSACURA2003MDX TOURINGREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCEIGNITION SYSTEMIGNITION COIL RELAY CIRCUIT TROUBLESHOOTING
2003 Acura MDX Touring
Ignition Coil Relay Circuit Troubleshooting
2003 Acura MDX TouringSECTION Ignition Coil Relay Circuit Troubleshooting
- Check the No. 46 (15 A) fuse in the under-hood fuse/relay box and No. 8 (15 A) fuse in the under-hood subfuse box.
Is the fuse OK?
- YES - Go to step 2.
- NO - Replace the fuse.
- Remove the ignition coil relay from the relay block, 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.
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Is there battery voltage?
- YES - Go to step 4.
- NO - Repair an open in the wire between ignition coil relay 4P socket terminal No. 1 and the under-hood subfuse box.
- Measure the voltage between ignition coil relay 4P socket terminal No. 4 and body ground.
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Is there battery voltage?
- YES - Go to step 5.
- NO - Repair an open in the wire between ignition coil relay 4P socket terminal No. 4 and the under-hood fuse/relay box.
- Check for continuity between ignition coil relay 4P socket terminal No. 2 and No. 1 ignition coil 3P connector terminal No. 3.Fig 3: Checking Continuity Between Ignition Coil Relay 4P Socket Terminal No. 2 And 1 Ignition Coil 3P Connector Terminal No. 3
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Is there continuity?
- YES - Go to step 6.
- NO - Repair an 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 ignition coil relay 4P socket terminal No. 3 and body ground.
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Is there continuity?
- YES - Repair a short in the wire between ignition coil relay 4P socket terminal No. 3 and the PCM (B12).
- NO - Go to step 7.
- Turn the ignition switch OFF.
- Connect the Honda Diagnostic System (HDS) to the data link connector (DLC) (see step 2 on GENERAL TROUBLESHOOTING INFORMATION
). Turn the ignition switch ON (II), and jump the SCS line with the HDS, then turn the ignition switch OFF.NOTE: This step must be done to protect the powertrain control module (PCM) from damage.
- Disconnect PCM connector B (56P).
- Check for continuity between ignition coil relay 4P socket terminal No. 3 and PCM connector terminal B12.Fig 5: Checking Continuity Between Ignition Coil Relay 4P Socket Terminal No. 3 And PCM Connector Terminal B12
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 (B12).
- NO - Repair an open in the wire between ignition coil relay 4P socket terminal No.3 and the PCM (B12).
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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.