CARspec recently had the opportunity to diagnose a 2004 GX470 that came in with a check engine light, VSC light, and TRAC off lights all illuminated.  As is often the case with late model Toyota and Lexus vehicles, the VSC and TRAC lights were triggered by the check engine light concern.

The code present in the system was P0325 – Knock Sensor Circuit 1.  The knock sensors in the GX470 (and in all modern Toyota/Lexus engines) are how the car’s Engine Control Module (ECM) monitors the engine for the correct ignition timing.  The knock sensors (one per bank on the GX470) are piezoelectric sensors threaded into the block that generate a voltage waveform when subject to specific frequencies of vibrations from the engine.  The knock sensors are tuned to listen for spark knock, ie. improper ignition due to to a variety of factors that can hurt the engine, and relay the presence of spark knock back to ECM via waveform so ignition timing can be modified to help alleviate the condition.

Knock sensors on Toyota and Lexus V8 and V6 models live in the valley of the engine.  This also happens to be where mice like to make their homes.  This GX470 had a guest that chewed through the #2 knock sensor harness during the building process:

GX470 Knock Sensor Mouse House

GX470 Knock Sensor Mouse House

Getting access to and diagnosing the above requires removal of the intake manifold, similar to the air injection issue discussed on later model GX470s here.

Knock sensor signals are sent to the ECM via shielded wire to protect from RF interference.  Because of this the wire cannot be repaired without the risk of the knock sensor signal being lost (really really bad) and a resulting check engine light.  The entire knock sensor harness was replaced.

Fall brings more concerns like this into CARspec’s shop as mice move in from the cold.  As Minneapolis, Minnesota premier Toyota and Lexus repair specialist CARspec is equipped to repair the above concern efficiently and correctly.  If you have a check engine light concern, don’t hesistate to schedule an appointment with us at 952-426-4798 today!