Author Topic: Flat battery last night, now engine management light. Serious? (Read 937 times)

PeBen27 · « **on:** June 17, 2023, 08:37:50 AM »

Either I or my darling four-year-old left the lights on on our 2008 Jazz 1.4 petrol yesterday evening.
No warning lights prior to that.
AA came out and used a jump-start battery pack, which worked a treat, but since then, the engine management light has been on. Is this likely to be serious, or are we still waiting for the battery to charge up and give normal voltage?
Thanks in advance.
Peter.
(PS. Quite enjoyed replacing the shock absorbers, springs and drop-links, quite enjoyed replacing the callipers and pads, dislike the replacement of the disks. Philips head screws, probably put in many years ago....hard work)

Kremmen · « **Reply #1 on:** June 17, 2023, 09:42:52 AM »

A flat or low battery will usually flag a Xmas tree dashboard with random messages.

Lord Voltermore · « **Reply #2 on:** June 17, 2023, 10:25:47 AM »

It could also depend on how old the battery is. Completely flattening a lead acid battery can cause permanent battery damage. A newish battery may recover and still function well enough but it might shorten its life. With an old battery the damage may be enough to 'finish it off. '

Have you fully charged it using a charger? If you are just relying on the car charging it up it may never reach full charge, even on a long trip, and especially not with short journeys.

If you havnt got one already I recommend buying a digital multimeter, From about £7. With accurate voltage readings in various situations and using some guidance from the internet you can get a good idea about the condition of your battery, and how well its being charged and holding its charge. A multimeter also has many other uses in the car and home. Battery specialist can do more thorough tests ,and may do free checks, but of course they ultimately want to sell batteries and repair/replace alternators .

If buying a battery charger pay a bit extra and get a smart charger that can cope with a bigger variety of battery technology, and can sometimes restore and revive a damaged battery.

Jocko · « **Reply #3 on:** June 17, 2023, 10:35:34 AM »

Some error codes (MIL) need to be reset to turn the light out. Others reset when the ignition is turned off. Seeing how hands-on you are I would suggest you purchase an OBD2 code reader like this one from Amazon.
https://www.amazon.co.uk/MOTOPOWER-MP69033-Universal-Diagnostic-Protocol/dp/B081635ZLF/ref=sr_1_2_sspa?crid=1HLV95YKBP1VS&keywords=obd&qid=1686994291&s=automotive&sprefix=obd%2Cautomotive%2C87&sr=1-2-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&psc=1
This allows you to read and reset codes.
Others will suggest a Bluetooth dongle and your phone/laptop with an app but I didn't have a lot of success with that when I tried it. I much prefer the standalone code reader. it just plugs into the OBD2 port to the left of the steering column and underneath the shelf.

embee · « **Reply #4 on:** June 17, 2023, 03:08:37 PM »

As others say, it's probably nothing. If the battery is flat the ECU will see voltages way below acceptable values when you turn on the ignition and will decide there are various faults. First step would be a cheap and cheerful OBD reader and just check to see what the codes are for reference, then clear them.
If you do need a new battery, try Tayna, a totally reliable supplier in most people's experience, almost always next day delivery.