Engine management warning light

Instead of asking a question, this time I hope I can give back a little. 

My gen3 has around 140k miles on it and as part of after purchase cleaning process, I added a system cleaning additive to the fuel to clear the engine system. I added 1 bottle to a full tank, and in 2 days drove about 90% of the tank out. I waited about 3 weeks and repeated the process, only this time I only drove out half a tank  (certain shortages at the fuel pumps caused me to halt the excercise). I really could feel how the vehicle performance improved.

Then I had to do some short trips and started to pick up a bit of roughess when cold. Dissapears when warm. Nothing major, but detracts from the smooth running engine I had experienced. I assume this is residue gunk that is getting into the system from the cleaning additive.

Yesterday the engine management system light refused to go out. 

Stopped driving after 2km and parked her at home. Researched the internet and came to the conclusion I needed a diagnostics test followed potentially, by a bank robbery or a sale of the family heirlooms. 

Spent last night researching some more... the vehicle runs fine apart from the little roughness that dissapears, oil is fine, fuel filler cap well seated, no funny noises or smells, nothing.

Found a post that suggested I disconnect the battery for 30 minutes and the system will reset and the light will go out. So I did just that. Had the battery disconnected for an hour. Reconnected and started the vehicle. Light gone. 

Went for a half hour (jimny) high speed trip on the local freeway and still no light. No roughness either.

My conclusion: the method works, provided there is actually nothing wrong. If there really is something wrong, I would expect the light to come on again soon. This weekend will tell.

Hope someone else finds this tip useful.

(Note to experienced forum administrator: if this novice Jimny owner is inadvertantly suggesting a method likly to turn a slightly ill Jimny into a pile of smoking scrap, please delete the post☺)
 

Disconnecting the battery usually clears data such as the 'long term fuel trim' but doesn't normally clear any engine codes.

If the Check Engine Light came on your ECU will have most likely recorded a fault. Disconnecting the battery doesn't normally clear the CEL, but in your case it has.

Couple that with your 'roughness' I suspect you have had some sort of problem with fuel trim which might have cleared after the battery was disconnected, but might also be masking another problem, possibly with fuel (dirty or water in it) or electrical (a sensor, possibly O2, MAF) or may be a coild pack.

Is your battery in good order, a top up charge might help first.

After that plug a OBD-II reader in to the port and check error codes, that will tell us what is wrong. You can get a dongle and phone software for little money.

Robin

I hate saying this but this is why I don't put any of these magical snake oils into my Jimny. The benefit you experienced with the running is most likely a consequence of using 40 litres of fuel in 2 days, this is often called am Italian tune up and is actually quite good every now and then. The subsequent rougher running and eml are probably directly related to it burning whatever the snake oil was and it leaving a residue or some such. Notwithstanding the above mentioned need to read the code stored in the ecu I would suggest running a couple of tanks of good quality branded fuel through it over a week or two to clean it out a bit.

Thanks to you both!.. being an engineer who installs sensors and makes a living analysing data, getting an OBD-11 reader is right up my alley. Regarding the snake oil, I contacted my local Sangoma back home (lucky I speak Zulu) and he confirmed that what I put in was just nicely packaged soap of some sort, and confirmed the improved handling was due to the lengthy high speed runs (which BTW I picked up off this forum as a thing to do).

Regardless, it feels good not seeing the light on!

wrote:

Disconnecting the battery usually clears data such as the 'long term fuel trim' but doesn't normally clear any engine codes.

If the Check Engine Light came on your ECU will have most likely recorded a fault. Disconnecting the battery doesn't normally clear the CEL, but in your case it has.

On most vehicles, and this includes every Suzuki I've worked on, disconnecting the battery will clear any codes in the engine ECU, having said that, if the fault has not been repaired, the ECU will sense it immediately on power up.

If you have a scanner you can test this yourself.

As I mentioned, after a 30 minute trip the light is still off, which implies that the fault has gone, but does not imply whether this is permanent or not. Could be that the fault is there, hovering just below the trigger level. My gut feeling is that the additive has released elements in the fuel tank, fuel lines or whatever before causing a small clogging of an injector, causing the temporary roughness. But this is absolute conjecture. Tomorrow (Sunday) after I recover from an all night shift supporting a team on track making the UK rails safe (my 1 month train ticket for the whole Munich zone costs the same as a single trip Huntingdon to London, are they crazy??.. another topic), I will take the vehicle for a lengthy run and see if the light gets triggered again.

On your advice, I have ordered a reasonable scanner which, according to the advertising blurb, will not only give me data, but real time graphs as well. I expect to get this as I leave for home in Germany. When I return I will investigate thoroughly and update. I wont try clearing any codes until I have checked with you all whether uploading software instructions to the 2008 Jimny is likely to cause software issues and lock the system down.

Your comments are well appreciated!