I have an 88 Ranger STX 2.3 and the check engine light won't turn on. I've checked all the fuses and they looked good and all the other lights are turning on and working fine. The only other issues are also electrical, the dome light for the cab has some burn marks where the bulb inserts and won't turn on the speedometer bounces up and down when I go past about 30 and the gauges for the temperature and fuel do not work at all. I need the check engine light to turn on and off so I can pass smog and am not sure what to do. I don't want to have to sell it over an issue so lame with a great running truck. Could anybody help me out? Any tips or anything as to what I could try or what it could be?

 

Welcome to the forum

Just a burnt out check engine light(CEL or MIL) bulb most likely
CEL bulb gets 12v with key on, the Computer(PCM) Grounds it to turn it on, pin 2 on the PCM is the Ground for CEL
This will be a Pink/light green stripe wire on the back of the instrument cluster and at the PCM Pin 2
I assume the vehicle runs................if not then PCM is bad so no CEL

In '88 the dome light would be controlled by a switch on the light or Main light switch Dimmer ****, and also door jamb switch, plunger style.

Usually the door switch was the GROUND for dome light, also switch ON the light was the ground.
So key off test for 12volts at the dome light, then test for Ground if door is open
Drivers door plunger could be worn out, it gets used the most
Can't say why there would be burn marks but clean bulb socket before putting in new bulb


Speedometer is cable operated in '88, classic cause of bouncing needle is broken wire in speedometer cable, it catches and releases on the sheath
Could be speedo gear assembly in transmission.
Pull off the cable, at transmission end, and use a drill to run cable up to speed to see if needle bounces, if so then cable is the problem.
It could be speedometer itself, just less likely


On the engine there are TWO temp detectors:
ECT(engine coolant temp) SENSOR, it has 2 wires and only used by the computer

And the ECT SENDER, sender only has 1 wire, like oil pressure SENDER, it is for the dash board gauge.
Sender will be on drivers side toward the back of the engine
Diagram here: https://ww2-secure.justanswer.com/up...124053_oil.gif

Remove that 1 wire on the sender and GROUND IT..........turn on the key, temp gauge should go to HOT, if so that means wire and gauge are OK, replace sender
Make sure you get a SENDER, parts guys will always pull out a SENSOR first time, they are not interchangeable, only a SENDER will work.
If you replace the sender then make sure the lower few threads are BARE METAL, sender MUST BE GROUNDED TO ENGINE for it to work

If temp gauge does not go to HOT then there is a problem in the instrument cluster, and that may effect fuel gauge as well, you will need to check wiring connector on the back of the cluster.

On the back of the cluster there will be a Yellow/white stripe wire, that comes from the gas tanks Float/sender, use OHM meter set to 200 ohms, then connect to a Ground and yellow wire
1988 was the last year Ford used 73-10 Ohms senders, 73 empty, 10 full
So ohm reading should be between those 2 numbers, rock the truck to get gasoline in the tank to slosh around, OHMs should go up and down as float in the tank does
If ohms stay at one number then float had a leak and has sunk to the bottom of the tank, i.e. OHMs are around 73 and stay there

If ohms are very high then yellow wire or sender in the tank is broken

If yellow wires OHMs seems to check out then Google: Ford anti-slosh module
Its in the instrument cluster

 

So far I fixed the dome light and check engine light both now work fine and in fixing the dome light fixed the radio and ac which I didn't know was broken. Dome light was just a fuse and the bulb and check engine light was also the bulb going to try to fix the gagues this weekend. Thank you for your help the reply was a life saver!

 

Goord work

Thanks for the update