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Discussion Starter #1
Installed an engine in a 98 Buick Lesabre. Started and ran fine for about 30 minutes, and then instantly died. No sputter, just died. Now it had no spark, no fuel. Figured it was either the ICM or the Crank position sensor. My understanding is the CKP is a pull down hall sensor, 4 wires. ICM supplies power and ground, and then there are 2 signal wires, that are supplied 7 volts from the ICM. When the sensor is triggered, it pulls the signal down to 0. Here is my problem.

When testing, with the CKP connector unplugged, both of the signal wires should show around 7 volts. The 3x does show 7 volts, but the 18x shows nothing. So I thought ok it must be the ICM. Tried another 1, same issue. Did I just get 2 bad ICMs with the same issue? Is it possible the CKP is killing whatever circuit it is in the ICM that supplies the 7 volts? Is there something else that could make the ICM not supply the 7 volts, like maybe security or the ECU? Stumped here and don't know what to check next. Can't check the CKP because its not getting the required 7 volts.

I thought about swapping the wires around at the ICM. Run the 3x signal into the 18x on the connector and the same with the wires going to the ECU just to verify the 18x is working, and theoretically the car should atleast start with them swapped, but run rough without the 3x.

Any ideas?
 

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If I were in your shoes, I would use a good diagnostic scanner and look at all the data stream info for what is and what isn't showing normal data. Another thing I have run across on 3800 cars is the wiring connecting to the ICM has some tendencey to break some of the wires....seems with age the insulation gets brittle and causes the wiring break. On another thought, with an issue like that it should be setting a code. Using a good scanner should show this. On another thought, maybe pull the cam position sensor to see if the magnet came off the cam sprocket. I have seen that happen on a few 3800s.

Get back with what you come up with..... Jake

PS, any chance you can try a different PCM??
 

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Discussion Starter #4
I have been using hptuners. Has fuel pressure. It didn't throw any codes. I have another ICM on the way, I'm going to check voltages on it before I connect it to any sensors or the coils. From everything I have read, PIN G and PIN H should have around 6.5-7 volts on them, when the crank sensor is unplugged. PIN H has the voltage which is the 3x sync signal, PIN G has no voltage which is the 18x Crank signal. Cam sensor tests fine. Normally I would think the crank sensor would be the issue, but that pin not having the voltage with the sensor unplugged makes it not seem that way.

Right now, the only thing I can think is its the ICM, or the PCM has somehow told the ICM not to supply voltage to 18x. Would seem like a feasible way to disable starting, but everything I have read so far seems like the PCM doesn't have the capability to do that. From what I have read, The ICM does all the work during cranking, then when the computer receives back at a crank position signal, it will supply 5v to the bypass on the ICM which enables PCM control.

I keep telling myself that I'm looking to deep so I step back and go over the basics and I always lead myself back to PIN G not have the voltage it should have.
 

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Here's another thought..... does the reluctor on the back side of the harmonic balance clear the slots in the crankshaft sensor?? And, is the reluctor tight on the balancer?? I have an OEM WIRING schematic from ALLDATA i just printed out. If you think this can be helpful, shoot me your email address and I will send that to you ASAP. Jake(mr goodwrench)

PS, the crank sensor can not be touching any of the reluctor blades.... Did you ever check the cam sensor magnet just inside the timing cover....it's mounted to the cam sprocket....

Did you ever check the PCM for any CODES??
 

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Discussion Starter #7
Turns out, I think it was the Crank Position Sensor. Replaced the ICM and checked the voltages, PIN G had the correct voltage. Started car, ran for 5-10 minutes and then died again. No longer has the PIN G voltage. Guessing even though the sensor is working, it seems to be burning something out of the ICM. Replaced the sensor, put another used ICM in it, and also checked the wiring to make sure it’s not grounding out. Car ran fine for several hours. No hiccups so far, not saying it couldn’t happen again and something else could be killing the ICM, but so far so good.
 

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When you feel confident the issue is solved, please send us another post. Good information for the rest of us just in case we run into that problem also.

Thanks, Jake and good luck.

On another note, there is something to be said about non OEM parts.....
 

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I am one who always believes aftermarket parts are better, but have run into issues where only an OEM part makes the issue go away. It really sucks too because I usually end up spending way more for the OEM part!
 

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I don't want to step on anyone's shoes here, but being in the after market service industry(for ever) has proven to me the OEM new parts are always top shelf. The next closest brand would come from DORMAN PRODUCTS. In today's world, there are so many "knock offs" from who knows where.

When it comes to "sensitive electronics".... I have always used OEM parts with excellent success. Only my 2 cents...... Jake(mr goodwrench).

Now on another note, in today's world even OEM products many times are not manufactured in the US. I have purchased OEM parts from a local FORD dealership and in large print on the box it came in said....MADE IN CHINA! I don't recall having issues with those parts....maybe during manufacturing for OEM they have a higher standard. Guess we will never really know. BUT the one thing that has been constant for me are the OEM dealer parts do seem to have an advantage. My 2 cents, Jake

PS, can you imagine where parts come from in SILICONE VALLEY CALIFORNIA!!
 
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