All 80 Series 1FZ Land Cruisers utilize two knock sensors that simply detect pre-detonation (knock) and will send signal to adjust distributor advance to compensate. Fuel quality plays a direct part in how the knock sensor does its job. These OEM sensors are very spendy but if you replace with OEM they tend to last a very long time. The Chinese knock-offs don't seem to last long at all. We see it all the time on customer rigs. There are two knock sensors and both use the same part number. The check engine light (CEL) that pops up will determine which sensor has gone bad. You generally only need to replace the one that is bad. If the connector or wire is damaged or broken, as they often are, you can replace with 80 Series Knock Sensor Connector/Wire.
