Ignition coils act as transformers, raising the voltage from a vehicle's battery to several thousand volts, which provides the power necessary to start the engine. The 2003 Honda Odyssey's ignition coils are placed underneath the intake manifold cover. Each ignition coil is also integrated with its own ignition control module, or ICM. Therefore, if the ICM is coming up on an OBD II scan -- or "on board diagnostics" scan -- the entire ignition coil will need to be replaced. Performing regular maintenance, such as replacing spark plugs every other year, will help to ensure the proper firing of your ignition coils.
Check the fuse panel underneath the left side of the dashboard and remove fuse number eleven, which protects the circuit for the ignition coils. If the fuse is broken, replace it with one of the same ampacity.
Open the hood on your Honda Odyssey and disconnect the negative battery cable by turning the cable eyelet bolt with a wrench.
Use a socket wrench to unscrew the mounting bolts for the intake manifold cover. Unscrew the mounting bolts for the ignition coils on either side of the manifold.
Use small pieces of tape and a marker to designate the location of each coil's electrical connection wires for reassembly after testing each ignition coil. Reattach the negative battery cable to the car battery.
Turn the ignition key to the accessories position. Use a multimeter, set to measure voltage, to test each ignition coil's connectors by touching the probes to the black-yellow wire for each electrical connection.
Turn the ignition all the way to the off position and use the multimeter to check the resistance between the black wire and the ground. If the multimeter reads infinite resistance, then there is a short in the ignition coil's connection wire, which either needs to be repaired or replaced.
Unplug the 31-pin connector cable from the PCM, or Powertrain Control Module. The PCM connector has numbered pin-holes divided into three rows, with the first row numbered 1 through 10, the second row 11 through 22 and the third row 23 through 31. Use the multimeter, set to resistance, to check the continuity between the ground on the ignition coil's connection wire and each of the following pin-holes: 3, 4, 12, 13, 14 and 23. If any of the pin-holes measure infinite resistance on the multimeter, then there is a short in the PCM's connection with the ignition coils. Reconnect the PCM's 31-pin connector cable.
Turn the ignition key to the on position and use the multimeter to check the voltage of each ignition coil's multi-plug connector. Use the probes to touch each of the six female terminals of the wires at the multi-plug connector. If the multimeter reads 0.5 volts, the ignition coil should be replaced. If there is not any voltage measured by the multimeter, then you are lacking continuity in the wires connecting the PCM and the ignition coil.
Reassemble the ignition coil wires using the pieces of tape. Reinstall the ignition coil cover. Tighten the ignition coil covers with a torque wrench set to 9 foot-pounds. Tighten the mounting bolts for the manifold cover to 12 foot-pounds.
