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Old 4 Weeks Ago   #1
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Question Knock Sensor

So the check engine light came on. The guy at the parts store plugged the reader in and says it's a "Knock Sensor" error. I have looked all over the internet and cannot find two sites that have the same information as to where this sensor is on the engine.

This is a 500 Sport (USA) with the 1.4L 16V engine. Once again, any hints, tips or links are greatly appreciated!

peace,
B
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Old 4 Weeks Ago   #2
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Re: Knock Sensor

Hmm, the code relates to the knock sensor but is it a faulty knock sensor or has it detected a knock?

Have you the code they read?
How was the car running before the check light, any misfire, stumbling, juddering, lack of power, bad mpg?

Can you pull the plugs and see if one is dirtier than the others?

I believe the sensor is up the back of the engine, on the block firewall side.
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Old 4 Weeks Ago   #3
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Re: Knock Sensor

Quote Originally Posted by Goudrons View Post
Hmm, the code relates to the knock sensor but is it a faulty knock sensor or has it detected a knock?

Have you the code they read?
How was the car running before the check light, any misfire, stumbling, juddering, lack of power, bad mpg?

Can you pull the plugs and see if one is dirtier than the others?

I believe the sensor is up the back of the engine, on the block firewall side.
Thanks for the reply, there have been no issues with driveability. No knocks, no stalls, nothing. It drives like a dream. A local auto parts store showed me the readout on the device they plugged in. I did not see a code number, only the "Knock Sensor" on the readout. I will check the plugs today.

Peace,
B
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Old 4 Weeks Ago   #4
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Re: Knock Sensor

Assuming the US 1.4 is the same as the 1.2. It's on the back of the block more or less in the middle above the starter motor. If you get it up on stands or ramps and crawl underneath yu can see it. It has an electrical connection running to it and it is held on with one bolt. 10mm from memory.
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Old 4 Weeks Ago   #5
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Re: Knock Sensor

My guess is it's no the knock sensor and the code reader the shop used isn't very compatible with Fiat's
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Re: Knock Sensor

Quote Originally Posted by Goudrons View Post
Hmm, the code relates to the knock sensor but is it a faulty knock sensor or has it detected a knock?
If it is a genuine fault, then it will be a sensor fault.

Knock sensors do detect knock often, that's what they do and is used as feedback to the ecu to adjust the timing (typically).
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Old 4 Weeks Ago   #7
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Re: Knock Sensor

Quote Originally Posted by vexorg View Post
If it is a genuine fault, then it will be a sensor fault.

Knock sensors do detect knock often, that's what they do and is used as feedback to the ecu to adjust the timing (typically).
What happens when the ECU cannot adjust the timing/fueling enough to get rid of the knock?

Say a cylinder is misfiring due to a duff plug or a compression leak, there's no other sensor to pick up that problem.

No amount of adjustment is going to sort that, so the cylinder knocks and the knock sensor reports it.

You could replace the knock sensor, but that wouldn't solve the knock as you've not fixed what is causing the knock.

Generally most sensors can generate various codes.
Some will be open or grounded circuit codes, these usually point to faulty sensors or broken wiring.

Other codes will be related to above and below threshold that the ECU just can't rectify or relate to in a drivecycle.

The first type of fault is usually self detected when the ignition or engine is switched on. The ECU powers the sensor with a 5v signal and gets nothing or 5v back so it knows there's an issue pretty much straight away as most sensors take a 5v feed, alter it and return the altered signal back to the ECU.
Even a working sensor with no input from what it's reading will return a small voltage back to the ECU (that's how it knows it's circuit is complete or broken)

The threshold related fault codes often have to occur 3 or so times in a single drivecycle, depending on what type of sensor it is.
It might "pend" a code the first couple of times but if the issue continues in that drivecycle it will often light the EML when out driving or running the engine for a while.

What's needed is a tool to read the ECU properly and be able to understand it.
Knock sensors usually come within the generic codes that all manufacturers use so basic diagnostic tools usually don't have difficulty reading that.

Shame you haven't the actual code as it would make identifying what's going on a lot more simple.
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Last edited by Goudrons; 4 Weeks Ago at 07:39.
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Old 4 Weeks Ago   #8
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Re: Knock Sensor

It should report a misfire on cylinder X, the knock sensor fault code would be for a faulty knock sensor, not that it cant correct for knock.
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