Honda Civiv 1996 -Knock sensor

VINCENT.HKCHUA

MEMBER
1996 HONDA CIVIC
4 CYL
FWD
AUTOMATIC

My 1996 Honda Civic SO4 EJ6 has a faulty knock sensor (OBDII - check) causing my MIL to be ON. I manage to get a second hand or used knock sensor and when I measured the impedance or ohmage, I get no continuity. Can anyone tell me what is the rough impedace I should get or is it normal to have an open circuit. I need to ensure that this second hand unit with an open circuit measurement is normal because to remove and replace this sensor is a very tedious exercise as it is below the intake manifold. Lots of work before you can access to the sensor. Thanks.

Regards,
Vincent

2 Replies

MHPAUTOS

MECHANIC
31,938 POSTS

No there is no easy way to test a knock sensor. They are a piezo-electric sensor, which can only be tested by exciting them with a frequency sweep(and typically high voltage). Each differenty type of sensor has different frequency 'modes', which is steps of frequency at which they will resonate. Even knowing the exact modal frequencies of a piezo electric actuator/sensor, it is still very hard to distinguish mechanical stresses and fractures in the material.

Easy answer is, 'no', sorry. If it's bad enough that the ECU is telling you it's bad, then there's no point in diagnosing further. Definately check continuity on all wires from ECU to the engine room harness(for the sensor), before buying a new one.