Honda Cr-V Fault Code/sensor Problem, Cont.....

[derekpara]

05 plate Honda CR-V Petrol.

Fault Code: P0325 ( Knock Sensor)

Engine warning light still on despite temporary removal with scanner and new after-part sensor being fitted. Elecrical connections checked and OK.

Professional and other advice seems to be that after-market part sensors aren't up to the job and almost certainly the cause of the return of the warning light. Remody seems to be to fit a genuine Honda sensor. ( Cost around £113, fitting £50). I will probably have to bite the bullet and cough up, but my question is, what does the sensor actually do apart from detecting the fault ?

If I get a genuine sensor it may extinguish the warning light for good but what about the actual fault itself ? Will the ECU adjust the engine function ? Any thoughts ? Oh, I've disconnected the battery and reset the ECU but the light still returns in a few minutes.

Cheers. D

[Hymie]

I’ve not encountered a problem with aftermarket spares not resolving a diagnostic fault code.

I would not ask my local Honda dealership to fit the genuine part – otherwise you might find yourself out of pocket to the tune of £160+ and no further forward.

My advice is to find an independent Honda specialist (they normally charge a fraction of main dealer prices) and explain the vehicle history.

With their advanced diagnostics kit (normally connecting to the OBD port using a laptop plus Honda diagnostic software) they should be able to determine whether the knock sensor is giving a genuine fault code that requires further investigation (or not).

[derekpara]

Thanks Hymie.

The fault code (P0325) seems to indicate 'pinking' which is an ignition timing fault. I can remove the code with OBD scanner but it comes back in a short while. So I know what the problem is but as I said in my question, what does the sensor do about it ? Just notify the ECU to deal with ?
No way would I use a Honda main dealer and there are plenty of auto electricians in my area who I know could do the work a lot cheaper. But are you suggesting that the fault code could be false and misleading ?

[tonyav]

It is to detect 'Pinking', derekpara.
https://cartreatments.com/what-are-knock-sensor-functions-and-symptoms/

[Hymie]

Having replaced the knock sensor, I would venture that there is a genuine issue in that the sensor is detecting the engine ‘knocking’.

You could replace the knock sensor until doomsday and the fault would continue.

I suspect that for some reason the knock sensor is being triggered – possibly by ignition mistiming or a mis-fuelling issue.

If you take the car to a garage and ask them for a quote to fix the issue, they cannot simply replace the knock sensor, since as you have found this will not fix the problem (but don’t tell them that).

But be very wary of giving a garage a blank cheque to fix the issue; make sure that they quote you to fix the problem – and if they fail to fix the issue, you would be quite within your rights to pay them nothing.

[derekpara]

Thanks for the interesting info, Tony. I can see my way clear now and I understand the function of the sensor.

Hymie, the over-riding opinion of several auto-electricians and garages is that the cheap after-market sensor is simply not up to standard and a genuine Honda part will help to adjust the timing and solve the problem of pinking. Thank you, too, for your sound advice.

[Zacs-Master]

A sensor won’t adjust the timing.

[bhg481]

The articles I've read say that the knock-sensor does adjust the timing in order to stop the knocking. Most engines nowadays have variable valve timing in order to cater for variations in the quality of fuel. There is obviously a limit on the adjustment so, perhaps, your engine is in such a condition that the timing cannot be adjusted sufficiently to stop the knock, hence the error code. You car is fairly old and the mileage and type of usage could have resulted in the cylinder head needing a decoke. Is the mileage high? Do you do lots of short trips? Is the car regularly serviced?

[Zacs-Master]

My apologies. Damn clever.

[derekpara]

Thanks, bhg. really interesting stuff. The car has done around 85k which is quite low for a vehicle of this age and quality, I think. It is serviced annually by a good fitter but basically the engine only gets the usual oil, plugs and filter change. I might try a change to a higher quality fuel or even a dose of Redex (?). I thought de-cokes were a thing of the past.
Thanks again, everyone.

[derekpara]

I forgot to add that is used mainly for short trips with the occasional (3 monthly) longer trip of fifty to 100 miles. I suppose it might benefit for a twice yearly oil change.

[bhg481]

I don't think "higher quality fuel" will make any difference, whatever "higher quality" means. Higher octane fuel (super) will only increase the tendency to knock (we used to call it pinking). You are right in thinking that decokes are largely a thing of the past due to engines being designed to run on much leaner fuel/air mixtures than in the past. The problem is with cars which do lots of short runs with cold starts, which means the engine is running on an enriched mixture and this results in carbon deposits in the cylinder head. I can't comment on how effective a dose of Redex would be. It used to be common to add it to fuel and I've seen it suggested that you remove the plugs and pour some into each cylinder. I only tried that once and the cloud of smoke was very embarrassing.
Have a word with your mechanic - he might suggest a compression test that could indicate head problems (or not) or some other test that could be carried out.

[derekpara]

Thanks again, bhg. Much appreciated.