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Old 09-12-2011, 10:48 PM   #1
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Default Link ECU not reading knock sensor

After reading previous posts, i ordered a new bosch knock sensor (for a Saab) and mounted it to the front engine mount stud that is provided with the FMII kit. I checked the wire going from the knock sensor to the ECU and repaired a few spots that were rubbed thin. I checked the resistance through the wire to make sure I had a good connection. I then checked the wiring from the plug on the ECU to the diagnostics box under the hood.

The knock sensor is still reading zero even if i tap on the block with a wrench. Any suggestions?
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Old 09-13-2011, 10:13 AM   #2
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You can replace your current lead with another prebuilt RCA cable, start a log and tap the sensor (unbolted from anything) on something metallic and it should log knock. If it doesn't then I'm guessing the problem isn't the sensor or the lead from the box to the sensor.
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Old 09-16-2011, 12:40 AM   #3
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Tested with new RCA lead and still no reading. Has anyone heard of the PIC chip on the board going bad? Any other thoughts?
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Old 09-16-2011, 09:56 AM   #4
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I'm posting responses with the assumption that you had the knock setup and working on the link and then it stopped. If not, then you need to do that first per the FM manual.

If the knock sensing was working and there's no logged now with the new cable, then my next step would be to bypass the OE lead you're using (what the link uses- I believe it's the AFM lead). You just need to identify the pin/lead at the ECU and swap in a new lead there. Then repeat the test above.

fwiw- I had a bad rca lead and used this to find the issue with a typical stereo cable- the log showed noise with the cable I swapped in.

If still no luck, go to miatapower.net, subscribe and then post up your issue. That's probably largest base of link users, including the guy who wrote FM's software.
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Old 09-21-2011, 10:40 AM   #5
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Thanks for the response Rob, i will definately check out miatapower.net.

The knock sensor was working and then it stopped. The RCA lead has now been replaced and i am still not getting a reading. the MAF lead has been checked and is good and the wires going to the diagnostics box under the hood were soldered in rather than poked into the top-side of the terminal as FM suggests.
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