Changed alternator and disconnected battery in the process. security system will not let me start the car

It could be many things, and I tend to favour the security system after a battery disconnect. Is the security light on?

https://www.google.com/search?q=2009+highlander+cranks+but+won%27t+start+after+disconnecting+battery

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Disconnect neg battery post release serpentine belt or alternator drive belt disconnect electrical connectors on alternator one plugs in one is secured by a nut on rear of alternator un-bolt alternator their will be either two or three bolts remove alternator and reverse steps to re-install

Disconnect the battery. Loosen the belt by rotating the idler pulley and remove the belt from the alternator. Disconnect the wires from the alternator. Remove the 3 bolts holding the alternator to the bracket. remove alternator. Reverse process for re-installation

If the engine will start, and the car is drivable, find the alarm and disconnect it until such time as you can get to a repair shop. If disconnecting the alarm kills the engine, then use a jumper wire to bypass it. If the car won't start because of the security system, I'm afraid you will have to have it towed to a dealership or repair facility to disarm it.

sounds like you have done more work than needed I wouldn't have changed your alternator, waste of money

1st check your battery with a multimeter (go digital if you can) theses are very cheap to buy, and you will use it a lot, set it to volts DC as per instructions start car and connect multimeter probes or clips to appropriate battery termianals, read display it shoud be 13.8 volts,, you now know battery cables and alternator are fine,, disconnect battery and do the same with multimeter on the battery again, leave sitting and watch reading if it goes below 12 volts over an hour your battery needs replacing.. If all good check when the battery terminals are back on tight and clean put the multimeter probes on termianls and ignition off and watch to see if reading starts to drop, if nothing turn ignition to accessories with everything turned off and again watch meter,, its a long process If you find it is still draining then pull a fuse at a time and check meter each time, if still dropping put the fuse back in and pull another one out.... repeat process till found........ before you start check glove box light isnt staying on, boot/trunk light is going off, ( put someone in there if you cant see) ,, If you have put in an aftermarket stero it may draw to much and you may have to upgrade your system, start with checking your battery

Hi,

Check the battery terminals/cables for security first.
If ok, then check any fuselinks inline, on the + cable (red).

If ok, then check MAIN FUSE in the engine fuse box - replace of blown.

If these are all good.....then, re-check the earth connections on the starter & alternator, including any other components/cables you may have disturbed when changing those items.

Cheers,

You disconnect the battery. Loosen the alternator tensioner bolts, the alternator securing bolts. Take out bad alternator to autoparts store and get a rebuilt one.

Take it to auto zone and have them run the free diagnostic and reset the codes. that should help.

It is a good idea (recommended) to disconnect the battery when working on electrical components. If you disconnected the batter, make sure the battery cables are secure on the terminals (clean terminals if necessary) - apply a terminal grease to prevent corrosion and acid build up. Also, check the connection on the alternator - it's very possible this may have been disturbed or disconnected by accident during the installation of wires. Part of your message says "my car won't start, I changed my water..." did you change your water pump? There may be a crankshaft and/or camshaft sensor near the water pump. Make sure that these are plugged in and secure. Check your ignition fuse in the fuse box, the starter relay(under the hood) and the fusable link,next to or near the battery, or starter. Check all electrical connection that may prevent the vehicle from starting.

security??dealer only iam afraid ,but try disconnecting battery temporary.then weather permitting check for a backfeed in altenator.quickest way is to remove wires on back and see if drains the battery still ,if it doesnt then theirs your fault ,its fairly common as a diode packs up in the rectifier pack.