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ok, since you are asking about voltages reaching the crank sensor, i have to assume you are following a diagnostic outlined in a book.

if the book is saying you should have voltage at this sensor, and you aren't, it's not always the computer doing these things.

first, check the wires, and the connectors, all the way to the computer.

if the wires are all good, then it probably is the computer module.

and, for the sake of mentioning it, normally, when a car computer dies, it either dies 100%, or it kicks into it's "backup" mode, and normally relies on the throttle position sensor, and the o2 sensor and makes sorta a guess at the rest of the values.

what i'm saying is that the computer almost never loses a single input or output.
 

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The crank sensor is an "input" to the PCM and should not really have voltage at it.

What is exactly going on with your Probe? Will it not start, or does it run rough?
 

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see, i was thinking the same thing, but it sounded like they were following a book.

but, i seem to recall that a crank sensor is nothing more than a magneto, producing small pulses of voltage into the computer.

above all, make sure you are following a book.

when i begged for this section, i did not intend for it to be in any way a replacement for the book, so, naturally, we are going to usually assume you are following a book.
 

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Not sure if there is a link problem with the AutoZone web site or the Probe is actually a Mazda with a different name plate??

Look at these links, they might be useful, if not, I guess AutoZone has issue??

It appears that the Mazda crank sensor does not have a 5 Volt reference, usually only the analog sensors have a 5 Volt reference, digital sensors may not always have a 5 Volt reference.

Testing 95 Probe Crank Sensor

Probe Wiring Diagrams

Hope this is helpful??

JamesO
 

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I would first check the ignition coil.

Use an Ohm meter and check the coil resistance for the primary input, usually fairly low resistance as I recall, somewhere less than 10 Ohms, some can be as low as 0.3-1.5 Ohms.

Secondary coil resistance is usually between the coil ground and the main coil tower output, resistance is usually between 3000-7500 Ohms as I recall.

If you cannot measure any resistance on either the primary or secondary side of the coil, it is is most likely open and therefore should be replaced. Make sure you properly measure before you condem a good coil.

Here is a link that may have nothing to do with your vehicle, but it is some good useful info on ignition testing.

Ignition Coil Testing

Ignition testing

JamesO
 

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i am having the same problem - i shut off my car, the next day it wont start. this has happened to me a couple times (i've only had the car since may) and every time i've had to replace the distributor. every time its the same thing, as soon as i put the new distributor in, it runs fine. some time later, it simply wont start again. i was able to get the obd1 code off the car - 02. according to some other website i found, this is the crankshaft position sensor (3 wires). i researched this and found that 2 (blue, green) wires go to the PCM (the third is a ground wire), and if either are grounded out, then there is a short. Well, one wire (blue) is grounded out ONLY when the PCM is plugged in. with the pcm disconnected, the wire is not grounded. does this sound like a PCM problem or do i have you guys completely confused?
 

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Good Evening dajester2007, From my experience whenever a distributor has failure, especially those that have the coil inside them, it was associated with either defective spark plug leads, insulators or enormously gapped worn plugs. (or a combination of them all)
Disconnecting spark plug leads and running an engine can also cause this problem.

What I suspect happens is that the high voltage either arcs internally in the coil reflecting effect into the driving circuit or the coil internally develops winding problems through arcing and excessively loads the drive circuit. (usually contained inside the distributor)

The symptom is commonly an erratic miss at idle for no apparent reason and can also be erratic accelleration under heavy load but has less effect when the throttle is eased.

You will notice that it is recommended that spark plug leads be routinely replaced periodically.

It can be a real nuisance to try to troubleshoot, and dismantling one of those distributors is not an option.

Cheers, qldit.
 

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can anyone tell me why i have no spark i have replace the crank sensor and dist
Good Evening john t, if you have replaced those items and the wiring and plugs all have good integrity it sounds rather ominous for the computer.

Have you pulled the computer codes?

That may tell you something?

Cheers, qldit.
 

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Good Evening dajester2007, From my experience whenever a distributor has failure, especially those that have the coil inside them, it was associated with either defective spark plug leads, insulators or enormously gapped worn plugs. (or a combination of them all)
Disconnecting spark plug leads and running an engine can also cause this problem.

What I suspect happens is that the high voltage either arcs internally in the coil reflecting effect into the driving circuit or the coil internally develops winding problems through arcing and excessively loads the drive circuit. (usually contained inside the distributor)

The symptom is commonly an erratic miss at idle for no apparent reason and can also be erratic accelleration under heavy load but has less effect when the throttle is eased.

You will notice that it is recommended that spark plug leads be routinely replaced periodically.

It can be a real nuisance to try to troubleshoot, and dismantling one of those distributors is not an option.

Cheers, qldit.
The plugs/wires are all brand new, new cap and rotor as well. I am not experiencing any of the symptoms you described either. I have an OBD1 code 02. According to this website: http://homepage.ntlworld.com/mx6-uk/malf/malfcode.htm
it is supposedly the crankshaft position sensor mounted below the harmonic balancer. I checked the gap and it is fine. I have checked the resistance on the sensor wires (Bl & G) and they are within specs. I checked the engine harness wires (Bl & G) to see if it is grounded out. The Bl wire is grounded out (according to the above website this is a bad thing). So I checked the wire - it is intact all the way back to the PCM. Once I unplugged the PCM from the harness, the Bl wire is no longer grounded. I am suspecting a bad PCM. I may be wrong though... idk anymore. Any suggestions?
 

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Good Evening dajester2007, actually I feel that the items should all be disconnected when checking resistances, otherwise you will get odd readings from inside devices and the voltage from inside the meter may cause further problems.

I have actually seen problems where ignition was lost and it was caused by the crank position sensor.

Although these are supposed to be simple devices and only sense every rotation, in some cases they actually contain electronic components and can fail.

The code you are receiving sounds like it may well be accurate, I don't like taking all that much notice of these codes but in this particular case it might be the best idea.

Can you possibly get one off a wreck in an auto wreckers?

I don't know any other path of trouble shooting apart from trying possible items.

If the engine is not being correctly sensed as rotating I doubt you will get ignition.

Sorry not much help.

Cheers, qldit.
 
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