so, i have a previous post here asking about bad ECUs and no spark conditions. i replaced both my ECU and Ignition ECU with a 933 and 169 respectively. I can pull codes from both but i always get a 1-1-1. I have also replaced my ICM and CPS for good measure. I am not getting signal to my ICM and thus my coil, what can i test downstream of the ICM to try and resolve this?

Assumptions: ICM is the ignition power stage. CPS replaced because its coil was open. Car is your daily driver, just died suddenly, a 245 with EGR from California. You can't post a link to your previous thread.

How many assumptions did I make in error?
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Art Benstein near Baltimore

If you lend someone $20 and never see that person again, it was probably worth it.

yes, power stage

i got an open reading on my DVOM from the CPS, the replacement is around 170 ohms.

I have never had the car running, but it was a daily for the PO who tore apart the ECU and ignition ECU for some unknown reason after the car suddenly quit cruising down the interstate to not have spark ever since. as best i can tell this was around

It is a 244 which i don’t believe has EGR, papers show it was purchased new in january of 90 in tennessee.

I get no signal to the power stage out of the ignition computer. it is possible the computers are not working, i did buy them used and cheap at that.

I have confirmed the fuel pump relay is activating both its circuits.

"the car suddenly quit cruising down the interstate to not have spark ever since"
First, I have carburetted 240s so this may not apply to your situation.
But the last time there was a sudden loss of spark, the ground cable from the battery to engine block had come loose.

I don't know if, in your case, the ECU would pick that up and give a code other than 1-1-1.
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1980 245 Canadian B21A with SU carb, M46 trans, 3:31 dif, in Brampton, Ont.

Good info Dan. I need to make some more silly assumptions now. You looked at the signal into the power stage pin 5 with an LED test lamp or an oscilloscope and saw a flat zero volts, and as a sanity check, saw the coil negative (terminal 1) was steady at battery voltage. If so, turn the key off and check the gray coax back to the ICU is not shorted shield to center conductor.

Also I will assume the PO had one problem to begin with and it grew to two or more during the course of his work. My assumption about California was based on your -933 fuel ECU, as the original would have been a -561 for Tennessee or -556 for California, I think. I will assume the car came to you on a rollback tow truck.

Also when you say the fuel pump is activating both its circuits, I assume you mean the fuel pump circuit is activated for 1 second at key on, that's all. If you're not, and you mean the relay remains closed and continues to run the pumps throughout your cranking, that means the ICU is getting the spark signal to the ECU, the injectors are opening, and because there's no spark you're sending fuel to wash down the cylinders and thin the crankcase oil.

At the ICU, the signal to the ECU for spark timing and the signal to the power stage are separate with different timing. Looks like this. The lower trace is what runs the power stage.







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Art Benstein near Baltimore

Expert: An "ex" is a has-been and a "spurt" is a little drip under pressure.

Your first assumption is correct, LED test light.

I don’t think the PO had any business dealing with electronics as he simply removed the covers from both computer units (and promptly lost them) and then attempted resoldering the chips, bridging most of them.

I found both of these module numbers from a list i discovered here, and both are supposedly known good replacements for this model year.

The coax is intact and not contacting.

I trailered the car home after buying for less than scrap, so your assumption is close enough.

I am not getting any pulses from the ICU. Does this mean the ICU is likely DOA?

"I am not getting any pulses from the ICU. Does this mean the ICU is likely DOA?"

I'm not much for the probability game. It is a gamble you could take if you quickly had access to another to swap, but not one I'd take if I had to buy one. The ICU has to be one of the most reliable parts of your 30-year-old car, normally.

Depending on what you have for test equipment, a swap might be your best option, but I'd want to rule out any trouble with the harness on the input side, from the CPS, and see the waveform or at least check continuity through the CPS coil back to pins 10 and 23.

If you know the tone ring is OK and no monkey business occurred putting on the flex plate or flywheel, you might be able to see the AC voltage generated by the reluctor on your DMM if you're at all practiced on your particular instrument. Be aware the Bentley documentation has it backward on which side is ground referenced. Be sure you have power and ground to the module if that's a needed reminder.

The -933 will work based on my own experience which I think I shared with Zach when he was putting together that compatibility list. I had one in an 89 for a couple years.





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Art Benstein near Baltimore

Never miss a good chance to shut up.

I just ohmed the cps at the ICU plug and it came out proper. Sort of at a loss for where to go next.

"I just ohmed the cps at the ICU plug and it came out proper. Sort of at a loss for where to go next."

Maybe you could have the car towed to a Volvo mechanic.
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Art Benstein near Baltimore

A truly happy person is one who can enjoy the scenery on a detour.

Well, we have a runner. After going through every wire in the engine bay, i moved on to where i should have started to begin with. I found a couple of the pins on the ICU harness very slightly corroded. After cleaning, the car started and ran amazingly smooth. I greatly appreciate your assistance!

There are two common issues with the 240 electrical systems I often forget to emphasize, frankly because they haven't occurred much in my fleet: Previous owner "fixes" and windshield leaks. Sorry. I should have mentioned the leaky windshield.
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Art Benstein near Baltimore

I used to be indecisive. Now, I'm not so sure...