I am a tinker and removed my '99 Infiniti Q45’s drivers headlamp to repair a crack. In the process I removed the air filter box and several items surrrounding it all with the battery disconnected. One item I had to move was a short braided wire running from the side of the engine to the chassis. When reconnecting, everything went fine, but I had to make a guess as to where the braided wire connected to the inner fender wall. It looked good until the Service Engine Light came on after a couple of days. The shop that changes my oil pulled up the ECU codes for me, they said both knock sensors on either side of the V8 were bad. My questions are:
Could the braided wire going to the wrong place cause a temporary and hopefully reversible change in what the ECU sees as a problem?
If I hadn’t disconnected my battery, could I have ruined my knock sensors?
When I do get this settled and my engine is performing happily with it’s knock sensors, will my mostly highway driving MPG improve?
Thank you!?
Why did you have to guess about where to reattach the braided wire? It should have gone right back where you disconnected it from. The engine-to-chassis ground is rather important, and if you connected it to something that isn’t providing a good ground you could have all sorts of problems.
“The shop that changes my oil . . .” That has a very scary sound to it. Is this “shop” a quicky-oil-change place, by any chance? If so, I suggest you get another opinion. I find it hard to believe that both knock sensors failed simultaneously.
I don’t think the knock sensors were damaged by your tinkering, and the battery being disconnected, or not, wouldn’t make any difference to the sensors.
As to your highway mileage, what do you get now, and what do you think you should be getting?
My desire to repair outweighed my desire to document where I loosened the braided wire, that’s why I am not sure if I connected it in the right location. : )
I don’t know much about knock sensors, so I just went on what the quick oil change place said. I actually went there twice and had them reset the ECU’s error codes both times with the same results. A week or more had passed between each visit.
Does it seem that the knock sensors could still be good or is this a snowball’s chance?
I get around 18 or 19 MPG, which is fine, I just want more justification, if needed, for the cash it will take to buy new knock sensors.
Thank you!
Your fiddling may just be coincidental to the check engine light coming on. I don’t think that both knock sensors would go bad at the same time. Bring the trouble codes here for (the collective) us to look at.
If the braided wire is a ground wire, any grounding place is as good as another – as long as ALL the chassis (body/engine) grounds are in place, making the engine grounded to the body, and to the transmission.
" I removed the air filter box and several items surrrounding it"
Take a close look at everything you disturbed and the stuff nearby.
Locate the knock sensors and check the connectors and wiring harness to them.
ECU codes at first visit are below. At 2nd visit, the 1447 error was gone leaving only the two relating to knock sensors. I last had the codes looked at too long ago to admit, but the Engine light remains ON. : )
P1447 EVAP Control System Purge Flow Monitoring
P0325 Knock Sensor 1 Circuit Malfunction (Bank 1)
P0330 Knock Sensor 2 Circuit Malfunction (Bank 2)
I found it really odd that both banks said they had a problem, unless maybe they use the same ground? I am ready to get back into this and see if the connectors are loose or broken. I have had little luck in finding a diagram or photo showing the proper location for the braided ground. Any more advice and thoughts about the codes from the ‘collective’ will be appreciated. Thank you all!