1989 Ford 5.0HO EFI check engine light

sandpitcobra · #1 (**permalink**) 02-06-2009, 11:41 PM

Can anybody tell me if the check engine light should come on when the ignition is turned on and only flash when you have a problem??

Thanks

blykins · #2 (**permalink**) 02-07-2009, 06:06 AM

If there's a problem, it should come on and stay on.

I'd like to hear some feedback from some savvy guys about this. I just completed a T5 to C4 conversion in my 1990 Mustang and now the check engine light is on. The bad thing is, my scanner won't pull the codes.

Woodz428 · #3 (**permalink**) 02-07-2009, 08:19 AM

It should come on when there's a problem, I had an '89 GT and recall that the light most likely came on when you first turn the ignition on as a circuit/light check. If you have concerns, code it out, that will reset the computer as well as tell you anything that may have fallen out of the parameters. Besides the injection, I think it may also get triggered by the low oil level indicator too. The water and air temps are part of the injection sensors so I didn't mention those as separate entities.
By the way, '89 was the first year of universal application of Mass Air and the last year prior to air bags, one of the reasons it's my favorite year....air bags...eccchh.
Blykins,You shouldn't need a scanner on that system, you should be able to use a test light on the underhood plug and count the flashes. Did you use the sensor on the speedo drive? It may have to do with the loss of the overdrive.

Humpty Dumpty · #4 (**permalink**) 02-07-2009, 10:14 AM

Blykins,

Code 29: Vehicle speed sensor

coryb · #5 (**permalink**) 02-09-2009, 08:27 AM

Go here, sign up and go to the 5oh EFI/EEC-IV/Carburetion forum. Joel is amazing at troubleshooting EEC problems.

Normally I'd recommend sbftech.com but they're down for maintenance right now.

Did you change out to an A9P computer or are you still using the A9L?

Ronbo · #6 (**permalink**) 02-09-2009, 05:01 PM

Past the initial lamp test it should not be on.

Short the test pin with a paper clip and count the flashes...

'Bout everything you'd want to know about Ford EFI systems is here: www.fordfuelinjection.com

To clear out all existing (old) trouble codes, disconnect the battery for a few minutes. Then run the motor and get the latest codes. (assuming the check light comes back on)

blykins · #7 (**permalink**) 02-09-2009, 06:56 PM

Guys, the VSS is still plugged in.

PANAVIA · #8 (**permalink**) 03-02-2009, 12:31 AM

I am using an A9L -- and its behavior is on during ign on, pre-start , then it goes off and stays off unless you have a bad connection to your tps, bad O2 sensor etc.

Steve