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After change batteries car won’t start

If Tero comes back, try changing batteries in the remote fobs. I’ve had coin cells that show full voltage but don’t give out enough current to operate. Some immobilisers shut down if these batteries are too low. Had a Colt the other day that had the batteries out of the keys for a long time and had to re pair the keys by replacing batteries then disconnecting vehicle battery for 5 mins. That said, I don’t know this truck so this is generic info. Sounds like an immobiliser issue to me but of course could be anything. Disconnecting + before - is only a problem if the loose + touches down which is highly likely unless great care is taken hence advice to remove - first.
last thing is when testing fuses always remove the fuse and test across it with a meter set to ohms. Visual inspection can result in thinking the fuse is continuous when it isn’t. Check all fuses and fusible links if there is any doubt


What puzzles me here is why the batteries went dead. This could be a fault with the alternator like a shorted diode or the capacitor fault with the ECU. The fact that the OBD is playing up as Shayne has said, does point to a possible ECU issue. It may be worth sending the ECU away to be tested. I don’t know of a reliable tester in Poland but ECU doctor has been reasonable in the U.K. Final issues are Suction Control Valves on the pump. Highly unlikely in this instance but can be a source of problems.

Other than checking that all wires have been reconnected to the batteries and nothing has been damaged or become disconnected by pulling wires or such when the batteries were manhandled in and out, there’s not much else.

One final thing to try as has been suggested with other ECUs is to disconnect both battery -ve s and short with the positive. Batteries will be disconnected and this will discharge the capacitors in the ECU. Leave this some time, overnight if you wish though I personally cannot see why a minute wouldn’t be 59 seconds more than enough.
 
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I don't understand why the battery in the remote could cause it not to start. ?
Correct me if wrong, but surely the chip held in the key contains all the information needed. With a flat battery in remote, the correct key/chip, would unlock manually, and when turned in ignition would start. Assuming every thing else ok, correct key with correct chip = unlock and start. ?
If you were out in the desert and the fob battery went flat with no replacement handy, you would be stranded, if that was the case. Ecu and fuses suggested by others earlier in thread.
 
Like I said, its generic info here as I do not own a 120 or ‘know’ them as others do. I’m simply offering another angle. The Colt I described had the same issue for the reasons I posted. Different vehicles have different ways their immobilisers work. Whether or not in the desert, this guys cruiser won’t start. Isn’t it in everyone’s interest to understand why and help if we can?

I think I gave credit on the ECU front and reinforced a point on fuses that can catch folks out.
 
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Your problem may be your key transponder. For some reason as my 90 series had a similar problem and would only try to start but not fire. Turned our to be the ignition transponder was not in sync with my key.
The puzzle you have is changing your batteries not sure would cause this..
Other suggestion is when putting your new batteries on have you somehow knocked a plug or something off.
Reading this post with all other members information and your answers everything you have been asked your lc3 seems fine.
This probably won't help you but everlittle helps.
Good luck with your fix and hope it's a quick cheap fix for you.
 
Some interesting info here..... I wonder if root cause of the problem was identified?
 
Info always good. Another one of those threads where the OP never says outcome, which could help others. Hasnt been seen since Dec 2020, so anyone's guess.
 
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