Resetting the code on my 04 mountaineer?

Question edited for clarity and typos.
Question moved to category.

Unlikely. Did you disconnect the battery? That would cause the anti theft system to need resetting.

Is the belt routing correct? Videos on changing and tensioning the belt.

https://www.google.com/search?q=2000+Mercury+Mountaineer+5.0.+replace+serpentine+belt

Belt routing and alignment. Incorrect alignment may make a dragging noise and increase tension.

https://www.2carpros.com/diagrams/mercury/mountaineer/2000

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Air bag there should be more #s or are you counting the air bag flashes?

why i don't know , get the OBD read this will tell the code's for faulty sensor/s/components etc, might just need OBD clearing

There's this website www.reliable-store.com
They have books on ALL vehicles.
it covers
wiring diagrams, electrical diagrams, fuse diagram, torque specs, PCV, error codes, fault codes, service info, repair info, parts info, owner's/service/repair/parts/maintenance manuals etc everything totally..
I have 1987 toyota 4runner model and I keep servicing and when needed repair it on my own. worth it !!!

. quick flashing when ? when trying to start the vehicle ? If yes you need to have it checked for codes . Do you know what DTC'S - diagnostic trouble codes are . If that light is flashing while trying to start the vehicle codes are present in the module that controls PATS . Instead of guessing have towed to a qualified repair shop . Because you have no idea how to diagnose this system .

You will need to enter the theft deterrent unique security code for your VIN and radio serial number given to you at he time of purchase of the new vehicle.

Try resetting the alarm, using the instructions given at the link below. I'll also copy the text here.

1. Insert the ignition/door key in the door lock on the driver's- side door of your Mountaineer.
2. Turn the key to the lock position.
3. Turn your key to the unlock position.
4. Turn your key to the lock position.
5. Turn your key to the unlock position. Your alarm is now disabled. If your key fob works, you can also press the unlock or alarm-disable button on the fob.
6. Start the Mountaineer's engine and allow the vehicle to run for at least 10 minutes. This will allow the alarm to relearn the default settings. You must make sure that you have disabled the alarm first, however, before you attempt to start the vehicle, so that the alarm will reset itself.

http://www.ehow.com/how_5978302_reset-mercury-mountaineer-alarm.html


If these instructions don't work, you can try resetting the car's computer by unplugging the battery for half an hour. However, that will reset the keyless entry code, as you can see in the fixya article I link to at the bottom

http://www.fixya.com/cars/t4755856-we_bought_it_used_and_we_dont_know_the_k

Just buy a code reading and resetting tool like ELM 327 - $10 on amazon, and connects to your phone via bluetooth. Then download Torque Pro free or paid for and additional $6.

you can't reset it. Try replacing the sensor.

SECTION 412-04: Control Components 2002 Explorer/Mountaineer Workshop Manual
REMOVAL AND INSTALLATION Ambient Air Temperature Sensor Removal and Installation

1. Remove the radiator grille. For additional information, refer to Section 501-08 .

1. Remove the three upper pin-type retainers in the radiator air deflector.

1. Position forward the air deflector.

1. Remove the ambient air temperature sensor.
   1. Detach the pin-type retainer.
   1. Disconnect the electrical connector.
   • Remove the ambient air temperature sensor.

Usually disconnecting the battery for anywhere from 10 - 30 mins resets any codes stored in memory.

Sometimes however it is a specific amount of "key cycling" that is required. eg: Turn key on, then off, then on for X seconds, then off for X seconds, then start engine etc. etc. etc.

If you have disconnected the battery, and there are no codes present but the light still comes on, there could be an issue with your airbag system. Wiring, or something was not done right.

WARNING : If you intend to work on the airbag yourself remember to disconnect battery for at least 45 mins. The air bag requires approx. 20-60 mins (depending on the vehicle, make and model and year) to discharge. If you do not do this you risk deploying the air bag, and that could ****!