Can anyone tell me what could possibly be causing right knock sensor to not generate a signal. ... On my 2000 VDP XJ8, I have twice replaced sensor with new. As background info, To resolve a P0328 knock sensor fault, I replaced right side sensor with new one. An ohms test to the sensor while the engine was running, failed to show any activity. So, I removed new sensor and replaced it with another sensor, then repeated the ohms test for 2nd time, with the same negative result. A check of the test to my driver-side knock sensor shows driver side sensor is operating correctly. ... I have no idea why I am not getting activity signal from knock sensor using an ohms meters in 200,000 ohms range. Knock sensor properly torqued to 14.1 ft/lbs. testing sensor only, unwired to cpm.

 

Did you take the measurements at the sensor or at some other point along the wiring.(possible wiring fault).

Is the new sensor fitted correctly, does it go in as far as the other one. If it's not close enough then you won't get a signal back.

Just a couple of thoughts.

 

Is it possible to change sides between left and right? In that case, if the code for the RH side clears you can rule out wiring fault there.. and you maybe would get an new faultcode for the LH...

Just to comfirm if you eventually have got two new faulty sensors..

If RH is still faulty, and is LH is still good... well, then you have ok sensors and there might be an issue with wiring somewhere for the RH...

/E

 

Thanks fellows for your thoughts.

Here is my situation: P0328 Rt bank knock sensor fault. I replaced passenger side / Right knock sensor with new one. cleared fault and drove for enough time to reset OBDII system. Using a multitester, I tested both sensors ohms level (200,000 ohms scale) to determine if the new knock sensor indicated a proper reading. The Left bank sensor tested properly while engine was running. But not the Right bank knock sensor (passenger side). Right knock sensor showed no signal being output at the connector while engine was running. All ohms testing has been done directly to knock sensor output connector (at end of "pigtail") with the engine running.

So, I bought a second knock sensor and installed it on passenger side (right), as I had previously. Again torqued nut down onto knock sensor at 14.1 ft/lbs. Tested the 2nd replacement knock sensor, and got the same test reading. No sign of ohm signal. So, I am confused.

It is not likely that BOTH of these new knock sensors are faulty.

What could cause the stud connector on the engine to not give a sign to the knock sensor?
Not tight enough ? .... both times torqued down to JTIS torque specification of 14.1 ft/lbs.
What else could it be?

Thanks for any ideas you may have.

 

It's not under any Jaguar parameter test but I will tell you this. The last 2 new knock sensors I ohm'd out before installing them were 202K ohms. That's 202,000 ohms just to clarify. If you still get the same code, what you need to do now is connect the engine wiring harness that goes to bank 1 knock sensor and crisscross to bank 2 knock sensor and visaversa to the other side. Essentially you just crisscross both knock sensor engine harness to the other knock sensors. What your trying to get at is if the engine code changes or stays the same.

 

Good suggestion.

The driver side gets near ohms reading that you stated.. but right side .. no reading..
My thought is that perhaps stud itself is somehow not allowing the same solid contact as Left / driver side.

How exactly do the knock sensor piezos work?
Mechanically they need to be "firmly" solid contact with engine block, but what else? in order to function?

 

The knock sensors work like a microphone. The only other way you can tell if the KS is any good is to have an ohm meter that reads much higher. Mine goes to 20 million ohms.

 

I've recently had an issue with a knock sensor, no output signal - I unplugged the offending side and put a meter on the prongs inside the KS connector, Ohm'd out OK. Did the same to the other side, same thing.
At that point I decided it was either wiring or connector, so flooded the connectors with WD40 and plugged it back it, started the car and no engine light. The connector was at fault, I guessed oxidization inside.
You don't need the ignition on to test the knock sensors, or plugged in.

 

Good Idea, Sean

Re Connectors good idea..
Re: "microphone" aspect
Only other thought I have is that knock sensor stud could be not properly "seated" so as to cause Knock sensor to not be solidly touching the block ... or some debris beneath that KS.

 

Has anyone here had luck testing the knock sensors by tapping on them and getting a change in the rpm's? I have read about this elsewhere and done it on other cars. When I tap on either of mine nothing happens. I have even disconnected the sensor from the block (with wire connectors attached) and down right banged on the sensor and still nothing.

I am getting a knocking/rattling noise under engine load between 42-47 mph. It is less when the engine is cold. I have ohm tested both sensors and they each read 198k.

Can the readings be OK but still something be wrong with the sensors?

 

A more modern ECU-s will not respond (retard the ignition, i.e. drop the rpm) when you bang on the sensor as it has electronic circuitry to recognise (and respond to) only the type of knocking produced by detonation in the combustion chambers.

You cannot really test a knock sensor using ohm measurement. With the sensor connected, you will first need to measure the DC voltages on each of its wires towards the ground - one should read 0V (or very close to 0) and the other should read 2.5V (these are usual readings on knock sensors and may not be the case on the Jag sensors but you can try and see what you get). The proper operation of the knock sensor is then tested by an oscilloscope connected to the 2.5V wire and light tapping on the area around the sensor (or on the sensor if unbolted). Instead of an oscilloscope, you can try with a multimeter set at AC voltage (2V range) and connecting one multimeter probe to the ground and the other to the 2.5V sensor wire. With the ignition on, see if you can get the AC voltage reading jump up and down when you tap on the sensor.

 

If that's not damaged the sensor beyond use I'm surprised!