Looking for e8tf-12a650-x2b ecm - 1989 Ford F 150

How can you misplace an ECM!

Your ECM needs to be preprogrammed with the VIN Number. You will need an auto-electrician.

NOTE: We will need your Vehicle Identification Number (VIN) in order to program the unit.
During the checkout process, please enter it in the text field labeled "Vehicle Identification Number (VIN)" located in the Vehicle Information section.

https://www.fs1inc.com/engine-computer-programmed-flashed-2003-lincoln-navigator-3l7a-12a650-ea-efd0.html

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If you're asking if you can swap in a different computer, the answer is no.
Where to get replacement PCM ECM or module Ricks Free Auto Repair Advice

I would be very suspicious of the Powertrain control module failure, it is a less than 2% failure rate. Was this a dealer who diagnosed this? If not do not waste your money the tech was likely wrong and said that because they have no idea how to repair the real problem. I know this scenario well, seen it a 100 times.

What size engine ? 5.4 L ? Your truck has coil on plug ignition system ! Has eight individual coils on top of spark plugs , center top of valve cover ..

The 5.4L and 6.8L engines are equipped with a coil on plug ignition system. This system has a separate ignition coil mounted on each spark plug. Operation of the coils is controlled by the powertrain control module (PCM) (12A650), which computes ignition timing based on inputs from the electronic engine control system sensors. For additional information on sensor inputs related to ignition control; refer to Section 303-14A .

Before you decide to replace the ECM did you test power to your component,and the ground circuit,

Majority problem on the ECU is the leaky electrolytic capacitors.
If you has the time to do soldering then you can fix the brain box for under $15 vs $120+ for a use one.
Just open the cover and look for damage (over-heated + leaked) capacitors.

Here is a listing of all possible computer modules for that truck. Perhaps this will help in some way in your search.

Elec Cont Unit (ECU), 8-351W (5.8L), (AT), Calif, ID E8TF-AL1A
Elec Cont Unit (ECU), 8-351W (5.8L), (AT), Calif, ID E8TF-AL1B
Elec Cont Unit (ECU), 8-351W (5.8L), (AT), Calif, ID E8TF-AL2A
Elec Cont Unit (ECU), 8-351W (5.8L), (AT), Calif, ID E8TF-AL2B
Elec Cont Unit (ECU), 8-351W (5.8L), (AT), Calif, ID E8TF-ALA
Elec Cont Unit (ECU), 8-351W (5.8L), (AT), Calif, ID E8TF-ALB
Elec Cont Unit (ECU), 8-351W (5.8L), (AT), Fed, ID E8TF-AN1A
Elec Cont Unit (ECU), 8-351W (5.8L), (AT), Fed, ID E8TF-AN1B
Elec Cont Unit (ECU), 8-351W (5.8L), (AT), Fed, ID E8TF-AN2A
Elec Cont Unit (ECU), 8-351W (5.8L), (AT), Fed, ID E8TF-AN2B
Elec Cont Unit (ECU), 8-351W (5.8L), (AT), Fed, ID E8TF-ANA
Elec Cont Unit (ECU), 8-351W (5.8L), (AT), Fed, ID E8TF-ANB
Elec Cont Unit (ECU), 8-351W (5.8L), (AT), Calif, ID E8TF-AP1A
Elec Cont Unit (ECU), 8-351W (5.8L), (AT), Calif, ID E8TF-AP1B
Elec Cont Unit (ECU), 8-351W (5.8L), (AT), Calif, ID E8TF-AP2A
Elec Cont Unit (ECU), 8-351W (5.8L), (AT), Calif, ID E8TF-AP2B
Elec Cont Unit (ECU), 8-351W (5.8L), (AT), Calif, ID E8TF-APA
Elec Cont Unit (ECU), 8-351W (5.8L), (AT), Calif, ID E8TF-APB
Elec Cont Unit (ECU), 8-351W (5.8L), (AT), High Altitude
Elec Cont Unit (ECU), 8-351W (5.8L), (AT), Fed, ID E8TF-AK1A
Elec Cont Unit (ECU), 8-351W (5.8L), (AT), Fed, ID E8TF-AK2A
Elec Cont Unit (ECU), 8-351W (5.8L), (AT), Fed, ID E9TF-Z1B
Elec Cont Unit (ECU), 8-351W (5.8L), (AT), Fed, ID E9TF-Z2B

if you are looking for a new computer with that part # i suggest contacting vintage autoparts in colorado. they purchase discontinued ford parts and store them for years...thats where our dealer goes to when obsolete parts are needed..it is very often they have it...good luck on your search....heres their link
http://www.vapinc.com/

Go on line to main ford dealer they are around 300.00 us dollors