How do you retrieve codes from 1990 ford taurus gl without dianostic computer. trying to help niece with car she bought. she can't afford to take into shop

Try this link for codes of your ford radio model:

1990 Ford Escort Car Radio Wire Color Codes

1990 Ford Taurus Car Stereo Wire Color Codes

Ok lets start at the beginning.
You may need a repair book and test equipment to fix this.
First, are you getting power thru the PCM relay ? The relay provides power to the fuel pump relay and the computer among other things.
That relay and the fuses that protect it can affect both spark and fuel.

I have the same problem few days ago, and still didn't find any solution. Can any one please help?????21

Should be part of the alternator

The best way is to use the vehicle VIN number, here is a link to a Ford Vin Number Look-up site, that will tell you the transmission code and the type of transmission you have:
https://www.fleet.ford.com/maintenance/vin_tools/default.asp

the starter solenoid is bad. very common in the older ford vehicles. had the same problem with my 85 Crown Vic and it was the solenoid. its like a 10 dollar fix. if it sticks after you replace it then theres something wrong with your alternator backfeeding the solenoid, which is usually because it is wired wrong.

I have a Taurus 94 with transmision AX4S, my problem is this not connect the gear 1, 3, and 4, show me the read code tester the code 645, 647 and 648, I need help thank you

the vehicle module sees a problem and without a scanner to retrieve the proper codes, it will be hard to correctly diag your problem....best to have a dealer/shop check that first.... GL

check the fuel pressure,replace the fuel pump-its in the tank

I have a 1996 Ford Taurus with a similar malfunction the intermittent wiper function is erratic, but the wipers park properly. I'm the original owner & this malfunction was in the car from the factory. I have a regular Ford Dealership manual & came to the conclusion that the Generic Electronic Module located behind the fuse panel is bad (computer glitch in programming) ! Ford Dealers want over $ 300.00 for a brand new module, I haven't checked with my local used auto parts recycler yet, but I know it will be less than the dealer price !