Check engine light

[Cowgirl Jen]

I changed the check engine light bulb on my 1994 ranger and now the light does not come on at all...how to find out whats wrong

 

[adsm08]

Well did it come on before and if so why did you change it?

 

[RonD]

+1 ^^^

Check Fuse #7 in Cab fuse box, 15amp, pull it out and CHECK IT, lol, a fuse can "look fine" and still be bad, much like a lady, no offense

The CEL(check engine light) bulb gets 12volts from fuse 7 with key on, but it has no ground so its off, until Computer boots up and Grounds it, which should take maybe 1 second after key is turned on


If fuse is OK, and you want to test further, open the hood
Between Engine fuse box and firewall you will find the OBD1 connector on the main wiring harness, it may still be connected to fuse box with a cap that says "EEC"

Look here: https://www.therangerstation.com/tech_library/OBD_I.shtml

There are drawings of the OBD1 connector
And the Self-Test OUT(STO) slot is labelled

That's the Ground from computer to CEL bulb, so you can put a jumper wire from a Ground(battery negative) to that slot
Then turn on the key and CEL should light up IF...........its connection in the instrument cluster is OK
If it doesn't light up then you will have to pull out the cluster again
This wire is a Pink/light green wire at the cluster, pin 8 on connector C251


If you want to test if Computer is Grounding the STO then connect a test light to Battery Positive, and to the STO slot
Turn on the key, test light should light up if computer is grounding STO like it should when it boots up
If not then could be bad wire from that slot to computer or the computer itself
Still a pink/light green stripe wire from OBD1 slot to computer pin 17

 

[Curious Hound]

One other thing. Did you replace it with an incandescent bulb? Or an LED? If LED, try turning it around. They are polarity sensitive.

 

[bobbywalter]

for sure.