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Battery Short

16 Nov 2019 17:43 #215696 by Bornagainoffroader
A couple of weeks ago I was driving along when for a second the radio cut out, on my return trip it happened again although this time everything stopped, no warning light's nothing, I rolled into the side of the road and went to open the bonnet, the problem was obvious before I even looked under it, it was stuck, welded to the bolt on the positive terminal, I think the previous owner had fitted the wrong battery as the terminals where on the wing side rather than the engine side, and the clamp bolt had arced out on the bonnet webbing when the cover had moved slightly. However when I tried to start it all lights came on and it started and I was able to drive home, the battery however was leaking through a vent and although for a few trips it started ok on about the fourth time it did not want to know, so I replaced the battery, that was last week and I have driven it without a problem until today, at one point on my drive it did a little stutter then about 15 miles on it cut out completely warning lights everything, I checked under the bonnet nothing loose and tried starting, it started but just enough to turn it round and it cut out again, this time it did not want to know, AA guy found his reader would not communicate with the ECU, he tried spraying starter fluid down the air intact whilst I turned it over, not even a splutter, so his diagnosis was what I was fearing damaged ECU, so my question is what other things should I test before going the ECU route? could it have damaged anything else that might give the same symptoms? Thanks

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16 Nov 2019 19:49 #215702 by facade
Replied by facade on topic Battery Short
What engine do you have?

If it is the single cam (pre Y reg, or a convertible), it needs a special suzuki diagnostic box to communicate through the obd port, I doubt if the AA man has one, so the ecu could be fine.

There is no spark if it won't go on easy-start, I'd be looking at the crankshaft position sensor as a first.

It might start again when it is cold, if it does it is definitely the position sensor.

If it suddenly breaks, go back to the last thing that you did before it broke and start looking there :)

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16 Nov 2019 21:01 #215704 by Bornagainoffroader
Replied by Bornagainoffroader on topic Battery Short
It's an 03 M13a, I have a scan tool as well and it kept saying can not communicate, the AA had a very top range looking reader and it said the same. It's just strange this is happening after the short out, I would have though it would have blown something, but if it was a main fuse nothing would be working, everything goes dead then a few minutes later it would start, only this time it's different, I just know you disconnect the battery before mig welding as large currents can bugger the ecu, this is very much the same thing. however I will be looking at it again tomorrow, see if it will start also disconnect the battery and re connect it to see if that triggers something, it just all points to the ecu it would be nice if it did burn out something like a crank sensor, mind you when this first happened one very strange thing did happen, on the way home the battery light was on, I though due to the overload, but once home I discovered the fan belt had snapped, it's quite new and showed signs of getting hot as it was shaped with 3 rounded pulley shapes, I thought that the charge had somehow froze the alternator or made it spin faster heating up the belt and making it stick to the pulley when I stopped snapping it when I started it up again, but it still charges ok.

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17 Nov 2019 19:57 - 17 Nov 2019 19:58 #215720 by Fossie
Replied by Fossie on topic Battery Short
It could well be the alternator... A quick check though fan belts posts reveals that the Jimny seems to have a tendency to snap fanbelt because the alternator bearings fail or get gummed up, so when a larger charge is needed it struggles and burns the belts .....( Just been through this scenario.) so if you have arced the battery , it my well have fried the reg/ rec side of alternator.
Your symptoms do seem to be earth related , though that is any electrical component obviously .
Just a thought.
Last edit: 17 Nov 2019 19:58 by Fossie.

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20 Nov 2019 21:12 #215810 by kirkynut
Replied by kirkynut on topic Battery Short
Is this the same one I've discussed on Facebook, which ended up being corroded relay wiring?

If so, I'm glad that you joined the Forum rather than stuck with Facebook as there's a greater atmosphere here and more knowledge.


The underdog often starts the fight, and occasionally the upper dog deserves to win - Edgar Watson Howe.

My Jimny Thread Here: www.bigjimny.com/index.php/forum/8-my-ji...on-continues?start=0

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21 Nov 2019 17:30 #215834 by DrRobin
Replied by DrRobin on topic Battery Short

Shorting the battery probably wouldn't damage the ECU. Given that the alternator was charging at the time, it might have damaged the alternator or wiring between the alternator and battery. You were more likely to have big voltage dips with a short, not over-voltage spikes, like with a welder. So I think your ECU is most likely OK. However, your alternator or wiring from the battery is more likely to be damaged.

I would check
- the battery voltage (on the terminals) should be 12v nominal (might be as high as 14v when charging);
- the wiring (White/Yellow tracer) between the alternator and the battery;
- the alternator;
- the voltage at the ECU or Cig socket.

The same wire and master fuse is inline with the alternator and the rest of the power system, so a fried cable or alternator might well be the problem. The insulation in the alternator might be damaged, is OK when not running, but as soon as it starts turning and warms up it shorts out. You could test for this by disconnecting the alternator or get it checked.

You could test the cable by measuring the voltage at the battery and at the Cig socket with some load, if the difference is more than 1v the cable is damged.

See the wiring diagram here

If you have damaged wiring or alternator it might be pulling the volts down and usually an ECU complains for low volts (less than 10v and you will probably loose the timing and might cut out altogether). If the electrical system load increases once the engine has started, then the car might start and then stall when the volts drop after a few seconds.

Hope that helps.


2011 Blue Jimny SZ3, Xtrons Head Unit, DAB, Front and Rear Cameras, TPMS, K&N, Bosch Aerotwin blades, LED side and interior lights, boot light, parcel shelf, boot box, dash box. Osram Nightbreakers, CTEK Battery Sense.

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