1. Fantastic. Glad to here the speedo is correct now.
My SPEEDO is ACCURATE NOW
But it's important to know exactly what fixed your problem(s). Please paste the entire contents of the 850log.txt (that records the DTC clearing, the B901 and B90D reprogramming and verification and all errors that occurred during that process, and any complete Scan, with the accompanying Summary) into the KWPD3B0 interpreter's Paste here
box, then press Interpret.
2. Concerning the 1.5 days and the 38 hours (and your assertion in the PM that only the mileage triggers the SERVICE light)...
Any of the 3 SERVICE Reset Interval (SRI) counters can trigger the SERVICE light coming on, *if* one of them exhausts its respective limit. Common European '98 S70 T5 limits are: 7500 km, 360 days (=1440 0.25 day intervals [but typically listed as 12 months or 1 year]), and 500 engine hours.
The SRI 1/4 Days counter = 1.50 days actually reflects 1.50 to 1.75 days, ie, 36-42 hours. 38 definitely fits in that range.
Almost always, if you've reset SERVICE light 1.5 days ago, your SRI Engine Hours counter will then be somewhere between 0-10 hours, depending on how much you've driven during those 1.5-1.75 days. The only time I could image Engine Hours counter reaching 38 hours while calender time was 36-42 hours would be during a near non-stop cross country USA trip or trans-Siberian trip.
But now that I think about it... What if the implementation of the Engine Hours counter is merely a record of how many hours Ignition is at pos I (or whatever position the ignition falls back to after starting the engine). Then:
a) if you had the instrument cluster out of the car, yet powered as if ignition was at pos I for 38 hours, or
b) if you left the cluster in the cluster in the car, left ignition on pos I for 38 hours (maybe because you had been listening to some music and forgot to turn the ignition off after turning the music off), then I could possibly believe SRI Engine Hours counter could increment to 38 Engine Hours in 36-42 calendar hours.
Interesting. I think I just learned something new.
Enough speculation. I no longer think there's reason to doubt the cluster because of the 38 Engine Hours in 1.5 days. And I no longer think those SRI counters are implausible.
3. Let's hope that your last ABS fix was performed *after* that "850 OBD-II" scan (reportedly on 2018-11-01) that recorded ECU 51 B90A = 05 00 (ie, 0005 hex) and that there has been no further incrementing of B90A since it reached B90A = 3B 00 (ie, 003B hex). I'll leave it to you to check that periodically. Because if it does increment **any**, then something is awry that might affect either the odometer and/or the speedometer and/or the mileage in ECU 51 B903.
4. In my USA '98 S70 GLT, changing ECU 51 B90D from 05 hex to 0F hex caused the Fuel Level gauge to lower about 0.560 US gallons (but it might take minutes for the lowering to complete). Changing ECU 51 B90D back from 0F hex to 05 hex caused the Fuel Level gauge to rise (very suddenly) about 0.560 US gallons.
I'd expect the same general behavior for your car, though the precise amount of decrease/increase might be somewhat different. At ECU 51 B90D = 0F hex the Low Fuel alarm will come on sooner than at the 97-98 S70 ECU 51 B90D = 05 hex (default value for S/V/C/XC70).
For more details, see B90D - Fuel Level Adjustment
and/or item 0D in jonesrh's ECU_51_B9_Meaning_of_Values_raw_notes.rtf
5. Concerning your "how to read ECU 51 B90A with 850 OBD-II app?" question...
Recent versions of "850 OBD-II" app scan ECU 51 B90A during the "Scan" function, then report that value in the Summary on a line similar to the following:
59 Hours of lost kilometres (per 1000 km)
That line was seen when your ECU 51 B90A = 3B 00 = 003B hex = 59 decimal.
I believe the "850 OBD-II" app interprets ECU 51 B90A more similar to how the Volvo Scan Tool (VST) does, **not** how jonesrh's KWPD3B0 interpreter (possibly erroneously) interprets it. The jonesrh KWPD3B0 interpreter is based upon my experience with my '97 850 T5. It might not be applicable to someone else's ABS failure behavior.
Looking at this ECU 51 B90A business in hindsight, I think it's moot. It's mere speculation how many miles were "lost" when ABS was failing. I wouldn't put much faith in either the jonesrh KWPD3B0 interpreter approach or the "850 OBD-II" approach or the VST approach at interpreting "lost mileage".
1998 Volvo S70 GLT - 205.5K miles - S70 & M44 testbed in 2016-2019; traded 2019-07-15 (for spare time)
1997 Volvo 854 T5 - 147K miles - 850 testbed in 2012-2017; junked 2017-09