I thought I would post this if anybody wants to share my pain while I practice my novel writing skills.

I have one of those (2-volume) big ol' stinkin' official GM Service Manuals (about 2000+ pages), one of which is just the "...Driveability & Emissions" volume for the 93 Bonneville.

Problems:
DTC code 42 (Ignition Control Ckt)
DTC code 18 (Cam/Crank Error) (less frequently)

Code 42 doesn't quite fit the standard of the diagnostics, since it SHOULD come on at idle. I have to race the engine. It may be running in limp home (or module) mode. It goes to running like it has a rev limiter, but only above about 2000 rpm.

Code 18: If I let it get up to op. temp and nail it while driving, that'* when it will also throw a code 18 (cam/crank sensor error) when I "gas it." But there'* more to the story.

Past related history:
1. Have had two TPS (throttle pos. sensor) go bad. 2nd one was an Autozone part and only lasted 2 years. This was to fix the problem of the engine rpm up and down at idle as high as 1500 - 2500, really fun in rush hour traffic.
BTW, good to know, both of them passed the voltage test, but ohming pins B to C (unplugged) would display multiple K-ohms of resistance at idle position. This should usually be real low, almost a short. Replacing TPS fixed both times.
2. Also have had an erratic no start problem that would rear its head every few months. Would, for no reason come out of it after any where from a few minutes to a few hours.
3. Noticed the exhaust smelling rich & mileage getting worse
3. Last week I headed out on a 25 mile trip to work (which would also acid test it for my wife since her trips are slow and short) and that'* when I saw the true picture
a. It did okay at 40 mph or less (low revs), but I had to nail it for a yellow/"pink" traffic light and it acted like it was hitting a rev limiter, running really crappy, but only at 2000+ RPM, shaking and vibrating with throttle. Now I am thinking it was in limp home or module mode.
b. It was GUZZLING fuel, like nearly a quarter tank in 8 miles!
b. Checked and found the code 18 and code 42.
c. After clearing the codes, the code 42 pops up first, once you have hit a little RPM. The code 18 comes in the same way, it seems, but only after warming up with a few laps around the block.

Work and findings so far:
1. I cleaned the ICM connector plug with carb cleaner and have also attempted to tighten the female pins' grips.
2. Ensured ICM was providing a ground out to cam and crank sensors.
3. Ensured I had continuity from ICM to PCM white wire (ckt 423) (resistance check from ICM pin to PCM pin w/long test leads!)
4. Wasted $130 on an unnecessary ICM. Same problem after replacing, maybe worse.

Suspect either a cam or crank sensor. A mechanic friend replaced one or the other several months ago (for the no start problem) in his home shop. But he cannot remember which and it was a cash transaction, so no paperwork on it. I cannot tell from "cleanliness" aspect either. Both connectors look dirty from the months of use. I read here where somebody had a similar code 18 that threw at warm up and revs & he found it to be the crank sensor.

I have been avoiding the crank sensor because of what I have read about the puller required for the HB pulley. I finally found some M6-1.0 x 90mm bolts as somebody suggested and will dive in this weekend. Anybody have any strong feelings regarding cam sensor vs. crank sensor?

I welcome any feedback or suggestions beforehand; and will update this post with another, hopefully shorter, chapter after. Hoping for " ... we have liftoff" soon.

Neither are too expensive or difficult to change, especially if you have an impact wrench for the crankshaft bolt. If you do change out the cam sensor, be sure to look in the hole, rotate the engine and verify that the interrupter magnet is in place in the cam gear. Although, if it were gone, a code 41 should have been set.

I finally got rid of the Code 42, by tweaking the female connector pins to the ICM. The original ICM is back in now.

I still am working to clear the Code 18.
-Voltage checks at the disconnected PCM lean towards the crankshaft pos. sensor.
-I worked for 2 hrs to try to get the Harmonic Balancer bolt out with an Impact.
-It looks like there is orange loctite on it (my impact has broken loose 300 lb+ bolts and this one is only suppose to be 111 lb .... arrrghhh).
-Wife needs the car in the morning, so cleaned the cam sensor and camshaft sensor connectors and wrapped it up.
So still have the 18 after nailing it at about 40mph.

I am toying with replacing the camshaft sensor first, since I am fighting the Seized Bolt Gods regarding the HB.
Updates to follow
:?

I used a breaker bar and a pair of vice grips on the flywheel in order to break the bolt from my balancer. Also soaked it in PB Blaster overnight before I attempted it.

And I was about to tell you to check for bent pins before I read your last posting. Good catch on that.

When the impact wrench won't get it done, or if you don't have an impact wrench...

With the car jacked up and supported, remove the flywheel cover and slip a big phillips screwdriver through one of the holes in the flex plate. Use a screwdriver shaft or a big bolt that is nearly as big as the hole in the flex-plate. Turn the engine counterclockwise until the shaft of the screwdriver jams against something solid. Don't let the screwdriver jam against anything that will break and keep the shaft perpendicular to the flex plate. That will hold the engine in place while you address the crank pulley bolt. Of course, the RF wheel and inner fender have been removed to give you a straight shot at the crank pulley bolt. Outside the fender, set up a jackstand to support a long 1/2" drive extension near the end where the handle will attach. A breaker bar is best here but a stout flex handle MAY not break if you are lucky. You may have to block the jackstand up to get it high enough. Make sure the socket is square and all the way on the bolt head. A six-point socket is best. Slip a cheater bar over the handle and apply torque by standing on the cheater. The setup looks something like this:


If you bounce down on the end of a 4 or five foot cheater bar, it will come loose, loctite or no. This is also an excellent way to test the quality of your tools.

Make sure you are square and all the way on the bolt head with a good fitting six point socket. If a helper is available, have him push in on the extension to keep everything properly aligned while you apply the force on the end of the cheater.

Excellent folks. If I don't have surgery this week, I'm going to give it another shot on SAT. And maybe slamdunk a cam sensor in the meantime.

Inclement weather forced me into the close quarters of my garage. I will back it in for the next round, where I can get at the flywheel at the same time. I also have a bigger (dia.) air hose that will reach that way. Wife forced me into too many social activities and only had 3 hours to mess with this on Sunday evening. Excuses, excuses...

And, yes, I have "tested" some 1/2" breakover bars with a "persuader" pipe. Broke the head off 2 Craftsman bars. But I'm game for a couple more if I have to. I'll be back.

Update from Tornado Alley:

Bonnie has taken to dying in traffic, repeatedly. Wife couldn't even make the 4-5 mile drive home as Memphis was getting blown into the next county while I am 25 miles away and out of touch. Got 3 squad cars to block traffic while they drug Bonnie'* cold body to a side street, and the wife got a free ride home in the back of a black and white.

On arriving for the big rescue, I had to jump start it since the battery was nearly dead from repeated starts after repeatedly dying. Once she fired, the idle was really crappy, nearly dying without tickling the gas the whole time.

The 3 miles home I had to run it down in 2nd to keep the revs up. Loaping along in drive would cause the motor to want to die, feeling the power steering going away each time. Arrrggghhh.

It was too late to tear into the crankshaft sensor tonight for that Code 18, so I tossed the dice and put in a shiny new Echlin brand CAMshaft Sensor. I knew it was all too easy. The only thing I gained was a shiny sensor.

Looks like I will be tearing into the crankshaft sensor as soon as possible, since the wife has requisitioned my Hemi Magnum, leaving me to suffer in my 78 Beetle 'Vert (spelled "Breezy Rattle Trap").

More news at 11!

I can use some suggestions.

I used the jack stand method to get the HB bolt out. Slick!
I read on another post about the M6-1.0 x 70-90mm bolts and a generic wheel puller to get the HB off. Double slick.

REPLACED the crankshaft position sensor tonight. '93s have a pin and book says no adj. required; pretty much locked into a fixed position. Vanes on inside of HB were nice and straight.

BAD NEWS: The code 42 is back (or was never really gone). Don't know about the code 18 yet since it is still on the jack stands and the 18 doesn't get thrown unless I'm moving and "gassing" it. Will make a test run tomorrow. The code 42 with Check Engine lite doesn't get thrown until/unless I rev it momentarily, maybe several times, sitting still, in Neutral.

During the quick revs you can hear/feel the engine hitting a rough spot maybe at about 3000 and up, just like before.

Also, at idle, motor will stumble and die, intermittently.

Ideas?
FYI: On code 42 troubleshooting chart, it suggests referring to the diagnostic paragraphs if certain paths peter out. That diag section has one option that refers you to the Knock Sensor ckt for a code 43. Don't know if I should "go there."

So far, I have replaced:
ICM, but then put original back in when it didn't fix anything
Camshaft Position Sensor
Crankshaft Position Sensor

Thanks for whatever help you can offer. :(

Good thing I have my FSM here at work

Looks like for the code 18....both the crank and cam sensors connect to the ICM, then pin L @ the ICM goes to the ground on the PCM, and pin F on the ICM goes to the cam signal input on the PCM. SO...here is what I would do now:

Check that ICM connector again to make sure all the pins are making contact with the connector (i.e. no bent pins and no loose-fitting connection points), and use dielectric grease. Then, if that doesn't work, take off the coils (clean those terminals while they are off and grease them too), take off the ICM plate and look under it. Is it full of gunk? Early models had no direct ground...instead they grounded through the bottom of the ICM plate to the mount. So make sure everything is clean down there so you can get a good ground (or do what I did and install a ground strap). Then if THAT doesn't work, you may have break in your ICM harness somewhere, or the ICM itself is suspect.

Now then, on to your other code....(thumbs through the manual)....ah....same thing applies here as well. I suspect ground issue, harness issue, or ICM itself.

Thanks Sandrock.
I took your advise and dove into the ICM connectivity again. I realize that I am fortunate to be in the semi-sunbelt and don't get the rust and corrosion. I even, just now, put a self-tapping 1/4" screw through the backplate of the ICM into the metal behind it. Printed off your response and going to check that out too.

In the middle of the ICM, where the shiny "brain box" is located, it has a piece of scotch tape looking stuff, maybe an inch long, with a black dot in the middle. I paid no attention to it until I noticed the replacement ICM I tried out had the same tape and spot, yet it is not OEM.
Q: Anybody know what that tape and dot is?

Poor Red Sled is still throwing both codes (18 & 42), has the crap spot if blipping the throttle or accelerating, immediately dies if let of gas at stop, etc.

Further findings that are unrelated. Looks like the LIM is leaking coolant and dripping onto the transaxle, right below the throttle body.
Q: Guess that is going to require pulling the LIM and replacing all the gaskets ???? This is all unrelated, though, right?

Second, even though the manual says otherwise, this motor appears NOT to have a Knock Sensor. Pix show it to be on the rear side of the motor, on the passenger side, wire into the same harness that goes to the speed sensor and oil pressure sensor, along with O2 sensor. Nope, nothing there; no wire or anything. There is a allen head plug in a hole where I think it is suppose to go, right above the oil pressure sensor. So, that eliminates any possible KS problem. Weird. I am the original owner and never any work in that section

Q: Final pair of questions for now; How likely is a bad PCM? Is a failure there very common?
How big a chance do I have of getting the wrong one from a salvage yard? What do I have to look for? Thanks for bearing with me.
Truly,
Bummed Bill is losing hair