Posted 1 September 2023

Q for mechanics

Hi

I drive a 2009 suzuki alto, the other day while driving the engine management light came on, amber on the dash, the car is running fine with no issues

I’ve disconnected the battery overnight but once reconnected and I start the car the light stays on

I’ve ordered an obd2 scanner waiting for it to arrive

My question should the light have reset even if just for a short time ? I’m thinking it might be an electrical problem

Thanks
Community Updates
New Comment

17 Comments

sorted by
's avatar
  1. adam.mt's avatar
    Not a mechanic either, but I'd say investigate engine management first before putting the blame on an electrical glitch.
  2. harrythefish's avatar
    Any truth in the rumour that a low quality OBD scanner can fry your ECU?
    .MUFC.'s avatar
    There's a potential for a cheapo to potentially short the OBD port, It has been known to happen.
  3. MonkeysUncle's avatar
    No it will still be there because it has a fault which it will immediately pick back up on.
  4. Toon_army's avatar
    Could be an o2 sensor, coil pack/spark lead or something else simple if the cars running fine.
    Hopefully the obd scanner helps you fix it for cheap
  5. Adriatique's avatar
    Author
    Just to update, scanned today and I’m none the wiser as the code thrown out is p0420, which accordingly is generic code to do with exhaust system, cleared the error wait and see if it comes back
    Willy_Wonka's avatar
    A majority of the time that will be a faulty oxygen sensor. You will have 2. One before the cat & one after the cat.

    You might be able to change the pre-cat one yourself easily but if it isn't that sensor the you need to get under the car to do the second, then it might not be that either.

    If the code comes back (which it most likely will) take it to a garage that can give you a full diagnosis & has the right scanner to do so. Or get an autoelectrician around. You will waste a whole load of money trying to work it out yourself. Trust me, I have been that mug before.
  6. .MUFC.'s avatar
    Could be a multitude of things, Just erasing a code or disconnecting a battery is unlikely to cure a fault. Sometimes codes can be cleared by disconnecting the battery but most of the time it'll require a scanner or the fault/s to be fixed otherwise it'll just reappear. Sometimes straight away, Sometimes in a varying amount of time. Could depend on multiple condition to trigger the fault/s.

    It's a good idea to read the fault codes. Note them down. Then erase them and see which codes return. Occasionally it may be a code that never returns. If/when the code/s reappear you'll have a better idea of what is wrong. Likely be a sensor of some kind at fault.

    A cheap scanner may or may not reveal the fault code/s. Some codes require dealer level diagnostics.
  7. Willy_Wonka's avatar
    I am not a mechanic but out of interest did you disconnect both terminals?
    Adriatique's avatar
    Author
    I did disconnect both terminals
  8. Dyslexic_Dog's avatar
    I'm not a mechanic either, but what's the point of an eml if it can just be reset by disconnecting the battery, a lot of people would just disconnect the battery to reset the light and continue driving without fixing the problem.
    Adriatique's avatar
    Author
    I think (I may be wrong) that disconnecting the battery is just a temp fix
's avatar