Don't get discouraged. I think both FSM and the info on the website are correct. Here is how it's possible - ECM supplies the 5v DC to the sensor, when engine is rotating, the sensor converts the 5v DC to 5v square wave signal (On/Off). If you look at the diagram, both 5v wire and the ground from the sensor go to the ECM. ECM might be picking up this square wave form on the ground side (sensing that it is fluctuating). So, FSM is correct saying that you should have 4.8-5.2 volt on the HARNESS side of the connector (you have to disconnect sensor to do this test). The reason they are describing this test, is the tools professional mechanics use, will show if you have a wave form signal form crank position sensor through the OBD2 plug, so in reality there is no need to do any other test on the sensor itself.

Now to the website you referenced. This is actually very helpful - follow their instructions they provide. Start with testing supply and grounds. If you have good 12v on red wire and good ground on the black wire, move on to the Test #3 to see if you are actually getting the On/Off signal from the sensor itself. It is a brilliantly simple procedure and it will show you what ECM "sees" just in slow-mo

As far as continuity from MFI relay to the sensor - you can connect a length of wire to the lead of your multimeter and extend the range that way. However, if you are getting 12v at the harness side of the sensor - you have continuity (this if where the voltage is coming form).

When you disconnect battery (or battery is dead), the codes get wiped out very fast. So you would not have codes stored from before. I was hoping that a code might be set by ECM due to not getting some sensor data and it will help with further diagnostics.

You obviously have an electrical problem. Even though you say electrical is not your strong suite, don't give up. Keep reading, test other sensors needed for spark. Check if you can find any info for the ignition module and see if any test procedures are available. Keep at it. Read the FSM, try to do the tests you can and eliminate as many components as possible. Eventually you will stumble upon the failed one.

 

BTW, if eventually you figure out that your troubles are due to PCM not working, you can look into rebuilding it rather than purchasing a new one.

 

Ha! That's my level of normal. Some people collect stamps, I collect projects. I had 6 cars/trucks...one runs. I've also got 2 motorcycles that are collectively in about 400 pieces at the moment. Naturally I had to go buy this Montero, right? Now up to 7.

I did the test from the website when I started this adventure. I got 12v and ground. My signal voltage was a consistent 2.35v. One of the things that has confused me is that most websites (and the FSM) say a bad crank sensor will prevent spark, but also prevent a pulse to the injectors. I have a pulse to the injectors. Maybe if the voltage was 0? Maybe the 2.35 is just enough for the injector pulse? I don't know. If my voltage was 0 it would be a pretty simple answer.

That was my assumption, which is why I hadn't put much effort into getting access to that relay. Good to verify though. Thanks. As I mentioned, I'm new to the Montero, so my learning curve has been reset.

I think I mentioned, the previous owners daughter said she was driving and "it just stopped". First thing I checked was fuses, then the fuel pump, then the ignition module. Went through all the checks in the manual and it checked out good.

I have a feeling I'm going to find it's the crank sensor. It's almost always the simple answer. What's that saying...if you hear hoof beats, it's probably not a heard of zebras? I have a little bit of experience with a Diamante ECM, and capacitors, so really what's driving me crazy is knowing what I've got to go through to get to that stupid sensor, realizing that it could all be for nothing if the ECM is bad, and that the FSM is a bit challenging.

So the crank nut is off, which actually required very little effort. Don't these have a history of coming loose? It's the old style bolt. Anyway, I'm working on getting the pulley off today, and we'll see from there.

Thanks for the input. I appreciate it.

 

HaHa, sounds like I found my doppelganger

Are you getting 0v and 2.35v alternating when you rotate the crank by hand? Or do you get 2.35v at the harness side from the ECM? That is below specs.

That is not normal. The bolt should be cranked to like 130 lb/ft torque.

I'm puzzled by the Montero just stopping out of the sudden as per previous owner's description. Did you ever check timing and compression on the engine? Since you have to get so far down to the timing belt to replace the sensor, you may want to make sure your timing is correct. Also, do a compression test once you put it back together.

 

The website I referenced says to use a wire-piercing probe, or back probe the connector for testing the signal. I did it slightly differently. I found a plug on a Diamante at a junkyard and cut it out with a couple inches of wire on either side. I stripped the wires and twisted them together, leaving them bare. Now I have a jumper that plugs in between the harness and the sensor, with a little bare wire in the center for testing.

I got that 2.35v as my "on" signal, and 0.05v as my "off" signal, when cranked by hand, as measured at the bare section of my jumper wire.

I haven't checked the timing yet. I haven't got it enough apart to see all the timing marks. I can tell though that the belt isn't broken.

I did a compression test when I first bought it. I can't find my numbers at the moment, but I recall they were kind of screwy. Low number was something like 90 as I recall, but it jumped to 150 or so with some oil in the cylinder. High number was 170 I think...something like that. I'll see if I can find them.

I posted on another site and had a few people tell me my motor was shot, but it was getting dark when I did the test and the mosquitos were tearing me up. I was rushing, and probably didn't get very accurate readings. At the time, I was thinking it was probably to be expected, given that the truck had sat for 6 months at least. I assumed the cylinders would be very dry, and give me weird readings. I was mainly just testing to see if I had a broken timing belt, or something equally catastrophic. I was looking for a reading of zero.

 

Very cool. You've made a MD998478 special tool
Ok, 2.35v with sensor plugged, what about testing at the connector on the harness side? What voltage you are getting there without sensor plugged in?

If you get 5v on the harness - replace the sensor. If you are getting same 2.35v (or rather voltage not in the 4.8-5.2v range), check the wiring and voltage at the PCM connector. You'll have to figure out which pin that wire comes from. If you are not getting 5v there - you might have an issue with the PCM.

Having low and uneven compression numbers does indicate some issues with the engine, but it should run. We can eliminate that from our reasons for not running.

 

At the harness, with the sensor unplugged, I get 12v at the red wire, and have a solid ground at the black wire. I didn't test voltage at the blue wire with the sensor unplugged. I was under the impression that there should be no reading there, since current flow on that wire is from the sensor to the engine computer. I'll re-check.