P0325 on a Toyota Highlander
P0325 means knock Sensor 1 Circuit Malfunction (Bank 1). On the Highlander, a few causes come up far more than others.
What P0325 usually means on a Highlander
P0325 is a knock sensor circuit fault that's well known on the early Highlander V6s — the same 1MZ-FE and 3MZ-FE engine family that saw it across the Camry and Lexus RX of that era. The knock sensors sit in the engine valley beneath the intake plenum, and their sub-harness wiring corrodes or the sensors fail with age. When the ECU loses the knock signal it retards ignition timing as a safeguard, so you may notice slightly softer throttle and a small economy drop with the light. It's a common, mileage-driven repair on these Highlanders.
Most common causes on the Highlander
- Failed knock sensor
The 1MZ-FE and 3MZ-FE knock sensors are a known wear item and fail with age and heat.
- Corroded knock-sensor sub-harness
The short harness and connector under the intake corrode on high-mileage Highlanders, breaking the circuit even with good sensors.
- Wiring or connector damage
Years of heat and vibration in the engine valley wear through the wiring insulation.
- Repair-related harness disturbance
Because the sensors live under the intake, prior work can disturb the wiring.
What P0325 costs to fix on a Highlander
The knock sensors are cheap, but on the Highlander V6 they sit under the intake plenum, so nearly all the cost is labor to remove the intake and reach them. Since access is the hard part, replace both sensors, the sub-harness, and the intake gaskets in one visit rather than going back in later. Expect a mid-range bill driven by that access time.
Fixing it
With the intake off anyway, do both knock sensors, a fresh sub-harness, and new intake gaskets together — chasing them individually on this V6 wastes the expensive labor.
For the full step-by-step diagnosis order (any vehicle), see the main P0325 guide.
Year, engine and mileage change the answer. Start a case and Redline weighs these causes against what your car shows, then names the check that would settle it.
Highlander owners also ask
Can I keep driving my Highlander with P0325?
A code alone can't settle that. The ECU retards timing to protect the engine, so you lose a little power and economy — but you're running without real knock protection, so get it fixed soon. If you hear pinging or knocking under load, stop driving and get it checked.
Why is such a cheap sensor so expensive to replace?
On the Highlander V6 the knock sensors are buried in the engine valley under the intake plenum. The sensors cost little; the expense is the labor to remove the intake to reach them.
Other codes on the Toyota Highlander
Related symptoms
Toyota Highlander problems & recalls by year
Based on widely reported patterns for this model; individual causes vary by year, engine and history. Generic P0325 behavior is covered on the main P0325 page. Confirm with a scan tool before buying parts.
P0325 on your Highlander?
Every problem becomes a Case. Tell Redline what your Highlander is doing: it shows what the evidence supports, what’s still missing, and what to check next, before you approve a repair.
“Inner pad ~1 mm. Outer pad 3 mm.”
Next: check the slide pins move freely before buying parts.