Parts for your 1989 Mitsubishi Pajero-Knock sensor

1989 Mitsubishi Pajero knock sensor — what’s fitted and what’s not

Based on technical sources, the presence of a knock sensor on a 1989 Mitsubishi Pajero depends on the engine. The 3.0L V6 (6G72) with ECI‑Multi fuel injection is fitted with a knock sensor, as documented in the 1989 Mitsubishi Pajero/Montero Factory Service Manual under Engine Control/MPI, where the knock sensor signal is shown as an ECU input for ignition timing. In contrast, the carburetted 2.6L petrol (4G54) and the 2.5L turbo‑diesel (4D56) do not have a knock sensor, their engine electrical sections and wiring diagrams include no knock-sensor circuit or diagnostics. This split is also reflected in period parts catalogues (Mitsubishi ASA/CAPS) and general workshop manuals covering Pajero/Montero of the era.

For owners of the 3.0 V6: the knock sensor is a small piezoelectric microphone bolted into the block that “listens” for detonation (pinging). When it hears knock, it tells the ECU to pull a bit of ignition timing so the engine runs safely on the fuel you’ve got in the tank. That keeps the V6 smooth, protects pistons and bearings, and helps fuel economy. On the Pajero’s 6G72, the sensor sits in the V of the block under the intake, so it’s out of sight but pretty important to everyday drivability.

Signs the knock sensor or its wiring is unhappy include poor performance, pinging under load, higher fuel use, or an ECU fault code for the knock circuit. Because it’s buried, replacement is usually done when the upper intake plenum is already off for other jobs (coolant crossover, injector seals, rocker cover gaskets). That’s the ideal time to fit a new sensor, check the sub‑loom for brittle insulation, and clean the block’s mounting pad so the sensor can “hear” properly. Always torque the sensor to the factory spec from the service manual and avoid thread sealants that can damp vibrations—clean, dry threads and the correct washer are the go.

A few simple habits keep it sweet:

• Use quality fuel appropriate for the engine, chronic knock from low‑octane fuel is hard on everything.
• Fix vacuum leaks and cooling issues quickly—lean or hot engines are more likely to knock.
• If you get a knock‑sensor code, don’t just clear it, inspect the harness under the plenum for damage and repair properly.

Why no knock sensor on 4G54 and 4D56 models? Those engines use carburetion or mechanically governed diesel injection with simpler ignition/fuel control. Without an ECU actively trimming spark advance per cylinder, a knock sensor wouldn’t have anything meaningful to command—so Mitsubishi didn’t fit one to those variants in 1989.

Popular questions about 1989 Mitsubishi Pajero knock sensors

How can someone tell if their 1989 Pajero actually has a knock sensor?
If it’s the 3.0L V6 with ECI‑Multi (EFI), it’s fitted. The carb 2.6 petrol and 2.5 diesel aren’t. Under the bonnet, an ECI‑Multi intake plenum and an ECU with a knock‑sensor pin in the wiring diagram are giveaways. Physically, the sensor is tucked in the V of the V6 block under the upper intake.

Where is the knock sensor on the 3.0 V6, and is it a DIY job?
It’s threaded into the top of the engine block in the valley. Access usually requires removing the upper intake plenum. A careful DIYer can handle it with new gaskets, a torque wrench, and patience, but many prefer to bundle it with other top‑end service to save time and labour.

What symptoms point to a crook knock sensor on the V6?
Sluggish performance, audible pinging on hills, worse fuel economy, or an ECU fault code for the knock circuit. Wiring damage in the valley is common with age, fixing the harness can restore proper operation even if the sensor itself is fine.