intermittent knock sensor check light, No fault code

[bensmith907]

Hello, Im afraid I have a intermittent knock sensor problem.about 6 weeks ago the car was driving like a pig, anything more that 2krevs it would missfire fault code 34 (knock sensor) flagged up.

I changed the spark plugs, cleaned the distributor and sprayed out the distribution lead ends, this fixed the misfire I erased the fault code and this has never come back since.


About a month ago on my way to work the check light was just flickering on/off (apparently this indicates a knock) checked the fault codes- No faults (55) conveniently on the same day I was fitting a new oil cooler so whilst I had it on the ramps I cleaned up the sensor and connector for the knock sensor, fault light hasn't been on since then... untill today.

on my way to work again today again the light flickers on/off still no fault codeIm pretty sure there's no knock because the car's driving really well and the 34 fault code hasn't rerturned. normally I would say just clean up the sensor and the connector again but surely if they were at fault then I would get a fault code.does any one have any experience with knock sensors- is it normal for the light to flicker if there is a knock, a sensor fail or a wire fault Im just baffeled there's no fault code to back up the lamp being on.

 

[johnny gtir]

have you removed the sensor at some point to clean it ? dont quite understand that bit of your post

 

[bensmith907]

no I havent removed the sensor

 

[bensmith907]

I ment to write I cleaned both sides of the connector

 

[johnny gtir]

no problem if you had removed it ie took the bolt out you can overtighten it or not tighten it enough both will cause fake knock but if you have not it must be something else

 

[bensmith907]

but even then wouldn't it bring up a fault code

 

[Fusion Ed]

If the ecu light is flashing then is a SERIOUS malfunction of the ECU. A knock sensor issue alone will not do that. I'd try an alternative ecu.

 

[bensmith907]

but its not like a steady flash, more intermittent or flickering

 

[bensmith907]

is the ECU behind the center console? Ill check the connectors first

 

[PobodY]

If the ecu light is flashing then is a SERIOUS malfunction of the ECU. A knock sensor issue alone will not do that. I'd try an alternative ecu.

That's what I was going to say so. - Flashing to tell you you've got knock is a PFC function.
Is it also possible it's an electrical issue elsewhere; alternator failing for example? If the ECU doesn't get 12V I don't think it's very happy.

 

[bensmith907]

Strangely enough everything was fine on my drive home this morning, this all stinks of wiring problems

 

[PobodY]

Ah... check the lights etc for shorting; if the plugs look all melted, that could mean there's no power to run any of the other circuits. - There are, of course, other possibilities, but I'd start there because it seems reasonably common.

 

[bensmith907]

when you say lights, do you mean the ones on the dash or the headlighst etc? because I have had problems with my headlighs before

 

[bensmith907]

actualy dont worry, I know what you mean

 

[bensmith907]

I has come on again today, I have noticed that it only ever happens after I have checked the ECU for a fault code. New ECU in the post so soon we'll see if that fixes the problems Im getting