Hi BB,

Its good to hear from you too!

Its bright and sunny Sunday morning here in Malaysia. At my job as Forensic Pathologist (thats Medical Examiner in the US) I usually don't heed speculations as they could be too absurd sometimes : ) No homicide case that needs my expertise yet today so I think I'd do some answers to your speculations!



Speculation no.1 - Audi "laser headlights"
I think thats more of marketing term in order to sell their cars better, for those buyers thats technologically inclined. Laser as you know it is a single waveform of light. Thats why you have red or green lasers. No white lasers by the way! Because you and I know white light is a mixture of colours! So thats one misnomer made by Audi. If their pixellated "laser headlight" could project some pictures on the road then might as well put some "conference room" LCD projector on the car's hood to light up the way. LCD projector nowadays are very bright too. Use some 12V DC to AC MOSFET inverter to power up these projectors on the car. By then you could show some animated pictures on the road too! Like to inform the pedestrian its ok to cross the road now?? Come on Audi you could do better than misleading the public. Sometimes I think these Germans are too much. "Desperate" is the word that comes to mind!



Speculation no.2 - The 555 IC fuel pump controller
Here's the web link:
https://www.volvoclub.org.uk/faq/EngineFIComputer.html#ECUFuelPumpControlCircuitRepair
Simply said this circuit is for those owners with faulty LH ECUs (ie unable to activate fuel pump relay). The circuit is supposed to use CPS signal from pin1 of LH ECU. That signal actually came from pin17 of EZK ECU as the CPS connects directly to EZK (not LH). If you repair (reflow solder) or recap your ECU I think you won't need this. That time the article was written ECU repair was expensive (still is) and most of used ECUs also expensive. Used ECUs are cheap now at eBay.



Speculation no.3 - Volvo didn't ground CPS harness at bell housing
I think you're referring to the CPS harness's screen ground. Yes its true Volvo didn't do that. The bell housing is also electrically grounded by its mating to the engine. Why then the CPS harness's screen is still grounded to EZK which ultimately uses intake manifold ground? I guess its good engineering practice to reference any sensor's screen ground back to its sensing circuit ground first. Don't agree with this? Many 900 cars are still working with this stock ground configuration.

Isolating the screen ground with capacitors (means no direct ground connection) usually works well in power supply designs (usually for switched power supplies) where the interference frequency is known (this to calculate the microFarad value of the isolation capacitor). Can't just cherry pick any capacitor and expect it to work.

Snap ferrite is usually installed in supply wiring like from power adaptor to laptop or mains input in switched power supplies. I've yet to see snap ferrite installed in sensor wiring. I guess you're being super-critical here.



Speculation no.4 - Your plan of what to do when it quits

Measuring here and there is good when you know what to expect and do next. Not if you're still beating around the bush. Maybe you could watch "Pine Hollow Auto Diagnostics" (PHAD) at youtube on how to do that. My favourite channel too, almost daily watched. Ivan's into using laptops, pico sensor, cylinder pressure sensor, current sensing devices in diagnosing problematic cars. My observation (and also to my relief) is that not one of 900 series Volvo needed these steps.


Hope these helps,
Amarin