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.
Coil Pack System
The EI system consists of a CKP sensor, coil pack(s), related wiring and PCM. The CKP sensor is used by PCM to indicate crankshaft position and speed by sensing a missing tooth on a pulse wheel mounted on front of crankshaft. The coil pack receives the signal from the PCM to fire at a calculated spark target. Each coil within the pack fires 2 spark plugs at the same time.
The plugs are paired so one plug is fired on the compression stroke, and the other plug fires the mating cylinder, which is on the exhaust stroke. On the next cycle, firing is reversed. On 6-tower coil pack applications the matched cylinder pairs are: No. 1 and 5, No. 2 and 6, and No. 3 and 4. See Fig 1 and Fig 2 .
On single 4-tower coil pack applications (4-cylinder), the matched cylinder pairs are No. 1 and 4, and No. 2 and 3. See Fig 3 and Fig 4 . On dual 4-tower coil pack applications (8-cylinder), the matched cylinder pairs are No. 1 and 6, No. 3 and 5, No. 4 and 7, and No. 2 and 8. See Fig 4.
The PCM acts as an electronic switch to ground in the coil primary circuit. When the switch is closed, positive battery voltage applied to the coil primary circuit builds a magnetic field around the primary coil. When the switch opens, power is interrupted and the primary field collapses inducing high voltage in the secondary coil winding and the spark plug is fired.
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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.
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