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Interesting Ignition Module discovery...


Quaraxkad

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A few weeks ago after changing an AC compressor, my Cutlass wouldn't start. I read a few threads here and tested everything I could. Fuel pressure was good. Voltage to the ignition module was good but there was no spark. Had the ignition module tested at Autozone. Resistance values on all the coil packs were within their limits. Looking more carefuly at my crankshaft position sensor wire, I noticed it had been cut and spliced by the previous owner for some reason, and parts of the bare wire were exposed. The clip on one of the connectors was also broken, so that cable was probably no good.

img6070ai4.jpg

 

I bought two new connectors and made a new cable. Replaced the crankshaft sensor also. While reinstalling I make an interesting discovery... My ignition module has a three pin male connector, and the sensor wire has a two-pin female connector!

img6073dl1.jpg

 

How did THAT ever work? How am I supposed to plug this in?

 

EDIT: I had male/female switched around. The ignition module connector is male, the sensor wire connector is female.

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:eek:

 

Was anything pluged into the 3pin before?

 

Yes, that crankshaft sensor wire was plugged in to it. The end in the picture was connected to the sensor, and the other end with the same 2-pin connector WAS plugged in to the ignition module.

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WTF!?!?

:eek:

 

Was anything pluged into the 3pin before?

 

Yes, that crankshaft sensor wire was plugged in to it. The end in the picture was connected to the sensor, and the other end with the same 2-pin connector WAS plugged in to the ignition module.

 

Then something somewhere was mixed and matched... Is that ign. module the right one for your car?

You might have gotten the wrong crank sensor?

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The crank sensor was identical to the one removed. It had a two pin male connector which was connected to the broken end of the wire in the photo above. The ignition module is the same one that was in there before. I'm pretty sure it's the right one because my '92 service manual shows that it should have that three-pin connector. I know that some crankshaft sensors use three pins and some use two. Is my sensor supposed to have three pins also?

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There's three connectors on the ICM, doesn't the CKP connect to the one that's by itself?

 

I thought it might at first, but the connector that's by itself on the other side (2-pin male) is right next to where the ignition module power connector comes out of the plastic loom on the wiring harness.

 

One thing that I didn't think of at the time, and might be the cause of this problem... The engine had been replaced with one from a junkyard by the original owner a few years ago. Different year LH0's may have come with either a 2 or a 3 pin crankshaft sensor. That could explain how a few things got mixed up, but it doesn't explain how the car has been running since then!

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I do not think there was ever any changes between ANY of the parts you describe.

 

How it SHOULD be: the wire from the crank sensor to the module is a single stand alone wire. it consists of TWO wires, one yellow, one purple, that are twisted 9 times per foot to reduce interference of the low voltage signal it carries. both ends should have male female ends. the sensor side has 2 ports. the module has 3 ports, the middle one going unused.

 

When I had a problem with this wire, i went to a friendly j/y and removed one complete from a donor car with the same motor (hence same length) granted it took two tries to find one worth re-using... and cost me nothing.

 

 

IF you are MAKING your own... you need to be sure that you twist it to prevent interference.

 

if in doubt... go pull one forma donor!

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I do not think there was ever any changes between ANY of the parts you describe.

 

How it SHOULD be: the wire from the crank sensor to the module is a single stand alone wire. it consists of TWO wires, one yellow, one purple, that are twisted 9 times per foot to reduce interference of the low voltage signal it carries. both ends should have male ends. the sensor side has 2 ports. the module has 3 ports, the middle one going unused.

 

When I had a problem with this wire, i went to a friendly j/y and removed one complete from a donor car with the same motor (hence same length) granted it took two tries to find one worth re-using... and cost me nothing.

 

 

IF you are MAKING your own... you need to be sure that you twist it to prevent interference.

 

if in doubt... go pull one forma donor!

like always x2. Just remember the module side does not use the middle pin

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How it SHOULD be: the wire from the crank sensor to the module is a single stand alone wire.  it consists of TWO wires, one yellow, one purple, that are twisted 9 times per foot to reduce interference of the low voltage signal it carries.  both ends should have male ends.  the sensor side has 2 ports.  the module has 3 ports, the middle one going unused.   

 

That's very helpful information, thanks! I took another picture of the one I removed, showing both ends with 2-pin female connectors:

img6075fv7.jpg

 

I have ordered a new connector (this one) that I can replace one of the existing 2-pin connectors with. Hopefully this will get my car running, but it still baffles me that this car WAS running with that 2-pin female cable hooked up to the 3-pin male ICM.

 

 

IF you are MAKING your own...  you need to be sure that you twist it to prevent interference.

 

I did twist the one I already made and wrapped it up in high-temperature braided nylon sleeving with heat-shrink tubing at the ends. My plan is to eventually get rid of as much of that useless, ugly plastic wire loom as possible.

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TA DA!

46846368448464.jpg

Ign. Module for a 3.1

Checked, and it's exactly the same on a 3.4.

 

I have the service manual and saw that page. Obviously it SHOULD be a three-pin connector with two wires on the ICM side, but it certainly wasn't before and the car was starting and running fine. It must have been plugged in just right so that it made at least slight contact with the correct pins on the ICM. Even after I made the new cable and connected it, BEFORE I noticed that the ICM had three pins, the car started up and ran for one day, and wouldn't start the next day. I'm heading out to NAPA right now to see if they have one of these connectors, if not I'll have to order it online or go back to the junkyard.

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have you replaced the crank sensor?

 

Yes

 

I have replaced the crank sensor and wires, the ignition module, and one of the coil packs is only a few months old.

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  • 2 weeks later...

Time for an update...

 

I had the car towed to a shop. They rewired the crank sensor and used the same 2-pin connector on both ends, plugging it into the bottom two pins on the ignition module (A and B). According to my service manual, B is unused, and it's supposed to be plugged in to A and C. Does anybody here have a CPS with a 2-pin connector and an ICM with a 3-pin connector? Can you tell me how yours is wired?

 

They also found a blown fuse (10-amp INJ). The car will run with a higher amp fuse installed in its place, but not for long before it blows the fuse and stalls. Could this be related to the CPS being plugged in to the wrong pins? Before the car was towed, I had the upper intake manifold removed to check injector resistance, and they all tested almost exactly the same (12.0-12.2 ohms I beleive). If incorrect CPS wiring would not blow the INJ fuse, I'll probably have to remove the UIM again and check for a pinched and shorted out wire.

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