In another post I had, I mentioned that my CEL light would come on during early morning starts, and when it was cool outside (maybe 50 degrees or cooler). This may have only been a coincidence, but I did not have this problem on warm days. The CEL would clear within 30 seconds to a minute, and never stored a fault (used an OBDII reader, but no faults stored).

I pulled my cluster the other day to replace some burned bulbs, and ended up putting the original cluster back in (I was using one from an Explorer - White face backround), and when I started the truck to verify that everything was lighting up/working, I saw that the CEL light was on AND the oil pressure gauge needle was parked. After about 20 seconds, the needle shot to the center, and at the same time, the CEL light went out.

Long story short, I replaced the oil pressure sensor, and the CEL has not come on since for the cool/cold mornings, and oil gauge is working (for what it's worth; I have "pressure").

In looking at the factory wiring schematic, it does show the oil pressure sensor wire (ground) tied to all other gauge grounds, and then to the anti-slosh module, which then has a lead to the CEL lamp.

My question: if a gauge is faulty, or has a faulty reading, is it setup to light the CEL? I can see a "check guages" in the cluster, but it does not light up (not used?).

 

Are you sure it wasn't the power wire tied to the other gauges and the CEL?

Oil pressure and temp gauges use grounds to control the needles, so they get 12volts when key is on, the temp sender is a variable resistor grounded to the intake/block, that changes resistance as heat goes up, the oil pressure sender closes(grounds to block) when oil pressure is above 6psi.

As far as the computer monitoring gauges, I am not sure, I wouldn't think so.
Computer has it's own temp reader(ECT sensor)
Computer wouldn't care about or need fuel gauge data
Computer does monitor battery/alternator charging on newer rangers, the so called "smart charging", jury is still out on that name IMO, lol.

Oil pressure is important and the CPS(cam position sensor) is usually located on the oil pump drive gear, so I often wondered if "they" would add software that would notify driver of possible oil pressure problem if CPS signal was lost, but it would just duplicate the gauge or oil light warning.
And loss of CPS signal does not mean oil pressure is lost, as we all know, these sensors fall apart.

 

In the factory schematic it shows the "lead" from the oil pressure sensor (which as you agree, provides the ground to the gauge) connecting to the oil gauge in the dash, and carries over to the anti-slosh module (see #12 in schematic below) which until now, I thought was only for keeping the gas gauge from flopping around when the vehicle turns or goes over bumps; looks like it also alerts an idiot such as myself that one of the gauges is not correct, or that the fuel in the tank is very low. From the anti-slosh module, there is a "lead" to the Check Gauge lamp and not the CEL lamp as I previously reported.

My eyes are the second thing to go. I feel like an idiot.

As Mark Twain once said, "Never argue with an idiot; they will only bring you down to their level, and then beat you with experience"

Here is that part of the schematic, which will clearly show "check gauge":

 

Yes, I see the confusion, the "Check Gauge Light" is tied in to 3 gauges through anti-slosh module.
So on low oil pressure, low fuel level, or high temp the "Check Gauge Light" should come on.

Not sure why CEL(check engine light) would come on though.
I do see that the PCM does monitor fuel level(sender) which is a surprise to me.

 

In my case, my old eyes saw CEL, but it was the "Check Gauge" light. For saving grace on my part, I'm going to see if the Explorer cluster I was using for awhile (switched back to the Ranger cluster) has these two cluster lights swapped.