,back lock latch horn stop working ,washer motor ,all at same time ...

Make sure your battery terminals are clean and tight.

Not sure about your car, but on my Chrysler mini van the same problem happened. The problem was not the motor but the body control module. The unit had 2 relays, but the BCM actualy controls the unit. To replace the BCM was $450. I bypassed the problem by installing an on/off switch inside the car and activated the motor by by passing the BCM at the relay. That was 3 years ago, still works great. Your BCM may be the problem. Check the schematics of the relays and try doing the same.

If you don't have the manuals, your local library has online access to most service manuals that you would have to pay for. Many time you can get access to them through their website if you have a library card. If not, go the library and get full free access to all the major car service manuals for free!

get the sensor checked out.it may not be opening fully

The truck has a feature, where you turn the key in door lock , the alarm should stop going off. there is a small switch on back of the lock cylinder. it may have popped off and is in lock position, but you cant turn it back to on position, because it popped off from the back of the lock. remove the door panel and look inside of the door where the lock is. make sure, that the switch is attached firmly to the back of the lock cylinder. start there.

it could be the power door lock motor on that door or the lock motor is not getting the signal from the module.some times the wires that run between the car body and the door break and need repairing.these are covered by a rubber tube that is fastened one end to the body the other to the door,you can see it with the door open.

no, sounds like its time for new horns, have someone push horn button while you check for power at the horn, if theres power then replace the horns,sounds like bad horns to me,good luck.

#1.. replace horn
#2.. check power & ground to W.W. pump.. if present.. replace pump.. If not, repair wiring.
#3.. replace door lock/unlock actuator.

hi , if like a similar problem i had years ago , the problem is either a bad connection on the steering wheel or an earth fault on the horn its self ? the car i had the fault on was a mk1 golf and under the steering wheel was a copper strip round the neck of the wheel where its connected to steering rod.....the connection (similar to a motor armature brush) was not making a good connection, i cleaned them with wire wool and hey presto. hope this helps??

Actually you use the horn relay a lot! At least 3 times every time you get lock/unlock your car (6 toots, 2 toots for lock and 1 for unlock right?) ... You just said: "as i clicked my car to lock. It got weaker and weaker until it stopped working" Buy a different brand relay (preferably one not made in China, pay more) and don't expect they WILL last a long time the horns take a lot of power and they have a very dirty feedback to the relay un-like lights. You can dis-able the toots by reading your owners manual.

i was having the same type of problem. we just put a couple of washers behind the latch and then adjusted the latch and it solved our problem.