Parts for your 2018 Toyota Mark x-Knock sensor

2018 Toyota Mark X Knock Sensor — What It Does and How to Look After It

Yes, the 2018 Toyota Mark X does use knock sensors. Toyota’s factory service information for the GRX130/133 series (covering the 4GR‑FSE 2.5 V6 and 2GR‑FSE 3.5 V6) describes knock control within the SFI system and lists diagnostic codes P0325 and P0330 for the knock sensor circuits. The Toyota Electronic Parts Catalogue for GRX130 also lists “SENSOR, KNOCK” for these engines. Those technical sources make it clear the vehicle is fitted with knock sensors—two of them, one on each bank of the V6.

On the Mark X, the knock sensor is a piezoelectric microphone that listens for the high-frequency vibrations caused by detonation (knock). The ECM uses that signal to trim ignition timing and protect the engine, especially important on the high-compression, direct-injected GR-series engines. It helps the car run crisp on our Aussie and Kiwi fuels and in hot conditions without risking piston or bearing damage.

There’s no scheduled maintenance for the knock sensors themselves, but a few habits help them do their job. Run quality 95–98 RON fuel, keep the cooling system healthy, and fix intake or vacuum leaks quickly—conditions that cause knock make the ECM work harder and can mask other issues. If the MIL comes on with P0325 or P0330, or there’s rattly pinging under load, lazy performance, or poor economy, it’s time to scan and inspect.

Replacement on the GR V6 is a bit involved because both sensors live in the V of the engine under the intake manifold, bolted to the block—so the upper intake has to come off. Many techs replace both sensors together and check the sub‑harness at the same time, as heat and the odd coolant spill in the valley can make the connectors brittle or corroded. Use a genuine or OEM‑grade sensor, route the harness exactly as per the manual, and tighten to the specified torque to avoid false readings. After refit, clear codes and complete a proper drive cycle so the ECM can relearn knock thresholds. No special programming is usually required.

If the car’s been through a coolant leak in the V‑bank or shows persistent knock codes after basic checks, it’s worth getting a pro to test sensor output and wiring before throwing parts at it.

Popular questions

Where are the knock sensors on a 2018 Mark X?
They’re mounted on the engine block in the V between the cylinder banks, beneath the intake manifold—one sensor per bank. Bank identification (Bank 1 vs Bank 2) follows the side containing cylinder 1, your service manual or a scan tool’s freeze‑frame data will confirm which bank has the issue.

Does a new knock sensor need programming?
Typically no. The ECM continuously adapts knock thresholds. After installation, clear any DTCs and complete a normal drive cycle so the control module can relearn. If codes return, check wiring, connector tension, sensor torque and intake leaks.

Is it safe to drive with a bad knock sensor?
The ECM will usually pull timing to protect the engine, so it may feel down on power and use more fuel. While a short trip might be okay, extended driving risks increased emissions and, if another issue is present, potential engine damage. Best to sort it promptly.