'90 Ranger ABS and coolant temperature gauge problems

I have a 2WD 1990 regular cab Ranger Custom with a 4-plug 2.3L 4-cyl engine, 4-speed automatic transmission.

The "Rear Antilock Brake" light is on. I'm of the opinion (having had to change one of the sensors on both Tauruses that I've owned) that the culprit is the rear wheel sensor on the differential. I'm also pretty sure that the three loose wires in the engine compartment that look like they plug into the side of the master cylinder are the problem. See, I just got the truck at an auction and need to have that light out to pass NY inspection. I have a solid black wire and two two-tone wires that have some kind of plug on the end that slide right into the connector on the master cylinder -- 5 will get you 10 that the black wire is the ground, but I don't want to just plug them in randomly and risk blowing the sensor if I can avoid it. I can swap out the sensor easily enough (I think) if that's the culprit, but if some jackass intentionally disabled the sensor by pulling the wires, there's no point in swapping the sensor out just yet.

Please bear in mind that I have very few tools and access to nothing more than I already have and that taking it to the shop is the absolute last resort for me because of very limited funds. I also have done no tests on the car due to the lack of equipment. Should I go to Advance Auto and have them run the OBD I scan tool on it before I even try to get those wires in? Would whatever the problem is even show up on the computer from a '90?

Also, the gauge for the coolant temp doesn't move, even when I fire the truck up. Any idea what's up with that?

Thanks in advance!

After finding some other people with similar problems, I have to add that I haven't noticed the jumping around at lower speeds people have commented on, but then again I haven't driven it much. The A/C in my car is much better than rolling down the windows. :)

Any suggestions on either problem? Thanks again!

Regarding the ABS problem, the sensor at the differential of course is a suspect but also input from the speedometer. Nonetheless, my advice is to get yourself a Ranger manual such as Chilton or Haynes. It will show you some basic electrical schematics which may help you troubleshoot the problem.

Troubleshooting the temperature gauge problem is simpler. Disconnect the wire from the sensor. Turn the ignition on (no run) and it should read max resistance (needle reading max). If it reads low, then you may have a short. Then short out the wire to the block with the ignition on and the needle should read minimum. If it read high then you have an open or high resistance in the wiring. If both tests went OK however, then the gauge is OK and the sensor is the prime suspect.

Thanks, DonSor. I have a manual on the way that may show which wire goes where, but I have the feeling I'll be doing plug and pray that I don't cause a fire or something. ;-)

It'll also point out where the sensor is (if I can get to it without ripping half the skin off my arm) so I can try that trick. Thanks!

on the lower intake above the thermostat there is a 1 wire TEMPERATURE SENDING UNIT.

take the wire off, ground it to the block and then check the guage to see if it moves, this is how you test the guage to see if it works.

if the guage works buy another temp sending unit at the store and put it on

Okay, either I'm an idiot, blind, or suffering from terrible luck.

I located where I think the coolant temperature sensor is supposed to be and there's nothing there. There's also, apparently, no oil pressure sensor. I've checked both sides and came to the conclusion that it's on the passenger's side. Is it on the other (driver's) side and I'm blind or an idiot? Or is it possible someone working on it removed the sensor and plugged the hole with something without tripping the check engine light? The Hayne's manual has shown me one confusing picture and the one showing me the thermostat has it narrowed down to about three different places on the front of the block, so I'm thinking I'm a total idiot at about this point.

Any further help would be greatly appreciated. Thanks!

hahahhahaha this is funny!

Most gauge temperature sensors are located in the vicinity of the thermostat housing in the front section of the engine block. It's pretty congested in that area so you may find a bit of difficulty finding it. But it's there. Also only one wire is connected to it.

Okay, I do believe I found it. The picture in the manual was backwards, go fig.

Then again, you're right about it being congested -- to get at where I suspect the sensor is I'd have to pull the serpentine, drop the alternator, possibly pull the power steering pump, and pull off the shield for the camshaft drivebelt. I think I see why this thing wasn't checked out when the problem first developed.

This has become a project for two because I just don't have the experience to do this solo. I think I'll figure out why the RABS light is on first and fix that before I worry about tearing half the accessories off the engine just to try to fix the gauge. The RABS problem might cause a failed inspection and I can't afford that.

Thanks for the help! I'll come back when I need more. :)

I don't believe you have to do all the items you have enumerated just to get to the sensor. Get an off-the-shelf manual such as Haynes or Chiltons from any auto parts store. It will show clearly the location and what you have to do to get to it. Because of close quarters. you may have to have a special wrench.

I have one. The pictures in it are great for the V6 engines, but the ones for the I4 are less than helpful when it comes to locating this thing. If the switch is on the intake side the only way I can get to it is through the alternator and what I believe it calls the timing belt cover. If it's on the exhaust side I'm screwed because there's nothing there. Maybe I'm missing something, but if I am, so's the manual.

Anybody know how to get the RABS fault code? Is the procedure the same for a '90 as on a '93? Are the codes the same? I'm sorry I'm so clueless but this is my first truck and all my cars have been late 90's era. The problems tend to be different... and an OBDII connector telling all makes it a lot easier to troubleshoot for us noobs. :) My Haynes manual is of no help for troubleshooting; it just gives the procedures for replacing the components.

The tempt. sensor is normally located on the engine block, right above the stat, not on the intake or exhausr manifolds.

I don't believe that RABS problems are included in the OBDII code list. You may have a bad ABS sensor located on top and forward of the rear differential.