Parts for your 2006 Toyota Highlander-Ignition coils

2006 Toyota Highlander ignition coils: what they do and how to look after them

Based on Toyota’s factory repair manuals and the Toyota Electronic Parts Catalogue for the 2006 Highlander (sold as Kluger in Australia and New Zealand), this model absolutely uses ignition coils. Both engines offered that year—the 2.4‑litre 2AZ‑FE inline‑four and the 3.3‑litre 3MZ‑FE V6 (including the Hybrid)—run coil‑on‑plug ignition. That means four coils on the 2.4L and six coils on the 3.3L, one perched on top of each spark plug.

The ignition coil’s job is simple but critical: it transforms the vehicle’s 12‑volt supply into the thousands of volts needed to fire the spark plug and ignite the petrol‑air mix. With coil‑on‑plug, there are no traditional high‑tension leads, which sharpens spark accuracy, improves reliability, and trims emissions. For a Highlander/Kluger doing family duty or long Kiwi and Aussie road trips, healthy coils keep starts snappy and fuel economy on point.

Ignition coils are largely maintenance‑free, but they do benefit from checks during routine servicing. At each service interval, a visual once‑over for oil in the plug tubes, cracked coil boots, or loose connectors is smart. Following the scheduled spark plug replacement (typically around the 160,000 km mark with iridium plugs, or per the owner’s manual) reduces coil stress and misfires.

• Common signs a coil is on the way out: rough idle, hesitation under load, poor fuel economy, sulphur smell from the exhaust, and a flashing check‑engine light.
• Typical fault codes include P0300–P0306 (cylinder misfire) and P0350‑series codes for coil circuit issues.
• Water ingress, oil contamination from cam cover seals, and age/heat cycling are the usual culprits.

When replacing, stick with genuine Toyota/Denso or a quality equivalent. Swap coils on a cool engine, seat the boots cleanly on the plugs, and torque the coil hold‑down bolts to about 8 N·m. If the V6’s rear bank coils are due and the upper intake needs to come off for access, it’s a good time to refresh the rear bank spark plugs and boots together. After any repair, clear codes and take a quick road test to confirm a smooth idle and clean pull under load.

Hybrid note: even though the Hybrid adds electric drive, the 3.3‑litre petrol engine still relies on coil‑on‑plug. Avoid blasting water under the bonnet, moisture in plug wells can trigger instant misfires.

How many ignition coils does a 2006 Toyota Highlander have?

The 2.4‑litre 2AZ‑FE has four coils—one per cylinder. The 3.3‑litre 3MZ‑FE V6, including the Hybrid, has six coils. All are coil‑on‑plug units mounted directly over the spark plugs.

What are common signs and codes of a failing coil on this model?

Owners often notice a rough idle, lack of power up hills, higher fuel use, or a flashing check‑engine light. The ECU may log P0300–P0306 for misfires or P0350‑series codes for coil circuit faults. Moisture or oil in the plug tubes and hardened boots are frequent root causes.

Should coils be replaced individually or as a set?

It’s acceptable to replace just the faulty coil. However, on high‑kilometre vehicles, multiple coils may be ageing together. If the V6’s rear bank requires intake removal for access, many workshops prefer to service that whole bank (coils/boots/plugs) in one go to save future labour.