Family Volvo enthusiast here. I'm looking into a 2001 S40 here.

Wouldn't start. Shop found:

No fuel or spark. Pointed at the ECM. Replaced crank sensor.

I got an used ECM, replaced the CPS a second time.

Car tries to start. Catches but won't go further. I don't think this is an ECM "programmable by VIN" issue as the car DOES try to start.

Replaced spark plugs. With the replacement ECM, it does get spark and fuel (I smell). But something's still off.

I notice the spark is not consistent, and random. Should have a rhythm and be consistent. What else should I look at?

See YT vids:

 

The ECM is tied to the car.

I bought a used ECM for my car to avoid paying for a software upgrade.

When I installed the used ECM the car cranked and cranked and seemed like it was going to start but it never did.

Once I put back the original ECM the car started and ran.

I would try and see if you can get the ECM programmed to work in your car.

 

Good info to know, thanks davidx1994

I wonder if there's a removable EEPROM in the ECM itself, and swapping EEPROM's from the original to the new ECM would "transfer" the car's propietary VIN info over onto the working ECM?

OTOH, I will look into programming services.

 

The chip can be taken out but it is really problematic.The board needs to be cleaned then the chip can be soldered out.Now you do this only to upgrade the existing program on the chip.You can not replace the chip with another or load a program isnt written by the same ECM.You stop the car then take the chip out.Programmer modifies the values you put the chip back.The car shouldnt be turn on until its all done as the ECU constantly writes and re-writes the chip and the check-sum has to match or the ECU will not recognize it.
Unless the car was flooded I wouldnt jump on the ECU being the problem wagon just yet.Did you measure the fuel pressure in the rail?How long the car was sitting?Does the injectors in fact firing right or just spraying in one line and not creating a mist?
Watching the video it seems that that spark is practically non existent.If you say you replaced the plugs but it still sparks all over the place on it.The OEM plugs are Bosch platinum's these however are something else.Your next step should be replacing the coils.
Then you can take the idle/air control valve and see if its stuck and clean it.
You need fuel,air and fire for the engine to run.It seems to me you are getting a brain surgery for a runny nose.

 

There is no removable EEPROM - I checked.

The car was not sitting for long. I did think it was flooded, but it just barely catches and dies. Matches the symptom mentioned in post #2 about a different ECM for the car, which needs programming. With the original ECM there was no spark at all. With this one spark is there, but not consistent. I smell fuel, so the injectors must be working OK.

I found a local Volvo place that will do the re-program for $140.