OBD codes / P0325 / Toyota Highlander
P0325 on a Toyota Highlander
Knock Sensor 1 Circuit Malfunction (Bank 1)
3.0L 1MZ-FE and 3.3L 3MZ-FE V6 (2001-2007).
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 likely causes on this model
- 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 it costs 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.
Highlander owners also ask
Can I keep driving my Highlander with P0325?
For a while, yes — the ECU retards timing to protect the engine, so you lose a little power and economy rather than risk immediate damage. But plan to fix it, since you're driving without real knock protection.
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.
Year, engine and mileage change the answer. Get a diagnosis for your Highlander — it weighs these causes against your exact configuration and real complaint data.
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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.