I could write a novel, but I'll try and keep this brief initially. I did a search and came up with lots of threads that just sort of end, with no post about what was wrong, whether they got it running...nothing. I hate when that happens.

So anyway, I've got a '99 Montero, 3.5. I bought it not running. The previous owner says his daughter was driving it and "it just stopped".

I've narrowed it down to a lack of spark. Fuel pump works, injectors seem to be getting a signal (I only tested one, with a noid light, because they're so tough to get to), ignition power module tested good. The coils tested good, though I figured they would. I couldn't imagine all 3 coils dying at the same time.

Anyway, I'm going through the manual online, trying to figure out what I can test. Many of the testing procedures in the manual call for an oscilloscope, which I don't have, and wouldn't know how to use anyway.

One of the things I tested is the crank sensor, but not with a procedure from the manual. I found a website that shows how to test it with a meter, which I did. It gets 12v, and it's got a good ground, but my signal readings are different.

The website says I should get 5v when the sensor is "on" and 0.1v when it's "off". I get 2.35v on, and 0.05v off. Here's the catch....the website instructions are for testing the sensor on a 3 liter motor, and I've got a 3.5, so I'm trying to figure out of my sensor is in fact bad, or if it simply operates at different voltage levels than the 3 liter.

I don't want to just throw money at parts, hoping it solves the problem. I want to know for sure. Otherwise, what's the point of testing it in the first place, right? Any input appreciated

 

Here is one link where the tech takes the guy thru the entire ignition side of things. Maybe helpful to you, poster quit replying without identifying outcome or cause

I have a 2001 mitsubishi montero V6 no spark.

 

Yeah, I ran into a lot of that while searching. Drives me crazy, and kinda rude too I think.

Anyway, I stumbled across some pages that indicate the Mitsubishi 1.8, 2.0, and 2.4 all require a 5v signal from the crank sensor, as well as the 3 liter model. I also found a page with test procedures for various Jeep models that require a 5v signal. I think it's safe to assume that 5v is pretty much the standard, especially within the Mitsubishi line.

At this point I'm pretty comfortable spending the money on a sensor. I'll see what happens and post back, for the benefit of future searchers.

Thanks for the link. I'll definitely check that out too.

 

Crank sensor reference signal should be 5v. This sensor outputs directly to PCM and all PCM sensors use a 5v signal. There are 3 wires going to the sensor. One is ground, one is supplied 5v. feed and the third one is the return signal to PCM. The signal wire will have a wave form but it will not have more than a 5v voltage. If you are getting 12v at the sensor, you may have some issue with wiring somewhere upstream.
I'd recommend you try to find the manual for your engine (on the sticky posts on this forum) and check your voltage again at the sensor and at PCM. Then check continuity of the wiring and for possible shorts (to positive)

 

Not to be questioning free advice, because I do appreciate any help, but are you sure about the supply voltage? All the other websites I've looked at for the various engines I referred to above indicate 12v supply voltage going to the sensor, and 5v signal voltage coming from the sensor.

 

If supply voltage to the sensor is 12v, how would you be getting out 5v on the output wire? The only way this would happen is if you have a giant resistor there, but this is not how this type of sensor operates.
Not saying that it can't be 12v. But voltage in should be equal to voltage out...

 

Not to be obstinate, but for the sake of anyone looking for this info in the future...

I downloaded the FSM from mitsubishilinks.com for a '98 (there isn't one listed for '99). In the Body/Axles/Electrical book, page 41 (section 90, page 36), the wiring diagram indicates 5v input to the ECM from the sensor, and no specification on voltage coming to the sensor from the red wire at terminal #3.

I'm not generally good at tracking electrical, so I was reading the instructions on how to read a wiring diagram. They indicate that if there is no specification on voltage then it is assumed to be 12v.

I picked up a sensor today. If I can get the crank pulley off tomorrow I should be able to get this new one on and see what happens.

 

First of all - good job finding the manual. This will help you countless times in the future when you have to work on your truck.

I stand corrected as far as voltage. I looked up the sensor specifications for the later models of Montero (what i have) and you are correct - one wire does supply full 12v to the sensor, second wire is 5v and the third one is ground. When engine is running the sensor output (5v) will look as a square wave. Regular multimeter should read between 4.8 and 5.2 volt on that wire. Check your ground and output at the crankshaft position sensor connector. If all looks good there, check sensor output voltage at PCM to make sure you are getting signal all the way there.
Does the manual you found have the step by step diagnostics for crankshaft position sensor (look up P0500 diagnostics).

BTW, since you are doing all the cranking and the engine is not starting, by any chance did the CEL came on yet? Perhaps you can pull a pending code from it to help point you in the right direction.

 

Well....not so fast. It could be our information source.

I printed out the pages of the manual that cover the MFI components testing, including the crank sensor. I haven't done the tests yet, for two reasons. First, step 1 is to check for continuity between the crank sensor and the MFI relay. The relay is buried in the dash, to the right of the glove box, and I can't even get a finger on it, let along get the plug off. I have no clue how to get to it without taking the whole dash out. Second, I don't have leads on my meter long enough to reach from the engine compartment to the under dash area.

I was looking at the procedure though, and I noticed something odd. In the FSM, section 13A page 88, the 4th step of the instructions say to check for voltage at the #2 pin on the harness side of the connector, with the connector disconnected. For a point of reference, this is the website I used to initially check the sensor -->
http://easyautodiagnostics.com/mitsu...-sensor-test-1

The FSM says I should be getting 4.8-5.2v. However, the #2 pin is the wire that carries the signal from the crank sensor to the ECM. If I'm testing on the harness side, with the plug disconnected, how am I going to get any signal at all? The current flow is in the opposite direction. I'm testing for a signal from the sensor, but on the harness side of the plug, with the sensor disconnected. It seems illogical. By contrast, the website I referenced above is very clear that the plug has to be connected to get a reading.

And this is where I get frustrated. On the same page of the FSM, in step one, the instructions say to "Touch the ohmmeter problems to both ends of the harness." I'm pretty sure they mean probes. The point is, it's a misprint, and I've found lots of them as I've gone through this. In addition, I'm now apparently finding test procedures that can't possibly give me an accurate result, as mentioned above.

Am I missing something? Like I said, electrical is not something I'm particularly good at. And, by the way, the manual says that if I don't get the correct voltage then I should replace the engine control module. There's nothing I found that indicates how to determine if the crank sensor is bad, unless that is also a misprint.

So now, no matter what test I do, I'm not going to know for sure if I've determined the crank sensor is bad, or the ECM. Either one would just be a guess, and I'm not really excited to tear apart the front of my engine to access a sensor, spend the money to replace it, and put it all back together to find that wasn't the problem. Also not interested in buying an ECM that I don't need.



Any thoughts appreciated. This vehicle is taxing my last nerve. I wanted to be 4 wheelin' long before now.

 

Forgot to mention...haven't gotten any CEL that I know of. The thing sat for 6 months with a dead battery before I bought it. I don't know how long a code would be stored under those conditions, but I'm not hopeful that there would be one. I could be wrong, but I don't have a code reader. I always just drive down to Autozone and have them do it.

I'll check again for the instructions on testing the sensor. I recall scrolling past that section on my way to chapter 13