Problem with CEL on my 1998 S70 GLT

[MoVolvos]

But I'm not sure if that would prevent the O2 sensor test from running too.

I would follow the recommendations except under 60 mph on the freeway for safety reasons. On the freeway the car is under less load so should burn cleaner and use less fuel that's why more MPG. Clean oil and good fuel will help with cleaner combustion as dirty oil will pollute if you have some blowby.
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[MoVolvos]

But I'm not sure if that would prevent the O2 sensor test from running too.

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O2 test should be start immediately and ongoing as soon as you start your car. The question is when does it reset? From what little I know it seems it requires several drive cycles before providing an input to whether clear the CEL or give one if you have reset the codes and didn't pass.

For info only, not advocating emissions tampering. I would look at the Appendix J to see if you qualify to be exempt from the Readiness. In NC 20 year or older cars are smog exempt. I don't remember the age in CA.
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https://carperformanceboss.com/resettin ... sor-guide/
https://vehiclefreak.com/how-long-to-dr ... sion-test/
https://roadweekly.com/how-to-trick-an-o2-sensor/

[wrybread]

Thanks for rhat. And I don't think what I'm doing with the evap test sequence is tampering, just gaming it a little. And my conscience is good, today I smoke tested the rear section of the evap lines (no leak) and inspected all the lines and junctions in front of the evap valve, no issues there either. Replaced the evap valve too for good measure. If there's an actual emission issue with my evap system it's incredibly minor.

[MoVolvos]

Thanks for rhat. And I don't think what I'm doing with the evap test sequence is tampering, just gaming it a little. And my conscience is good, today I smoke tested the rear section of the evap lines (no leak) and inspected all the lines and junctions in front of the evap valve, no issues there either. Replaced the evap valve too for good measure. If there's an actual emission issue with my evap system it's incredibly minor.

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In terms of tampering, I was referring to one of the links I suggested for reference and information not what you are doing.
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[abscate]

The OXS and CAT monitors require 30-60 second times of overrun, with the fuel injection turned off , while the ECU measure front and rear OXS to see if these components are functioning. That’s the ‘“coasting” time on the drive cycle.

The fastest I’ve ever completed these is 25 miles, usually ot 125 miles or so. It’s not easy to find a traffic place you can coast down from 45 mph in mid LI!

This guy goes deeper into OBD and readiness than most any other…

https://www.rlescalambre.net/handling-i ... s-monitors

[wrybread]

Thanks. And I'm curious, does running the AC stop the oxs and cat tests too, or just the evap? Or am I wrong about it stopping any test at all?

[wrybread]

It's been a marathon few days working on my car. Replaced by O2 sensors and then quickly passed the O2 Sensor test, now the only tests that haven't finished are the Evap Sys and Secondary Air Sys.

Does anyone know if the Secondary Air Sys test will complete when there's a full tank of gas? I'm trying to delay the Evap test from running if possible, even though I've now swapped the evap valve and a couple of lines. I'm not seeing any leak but at this point I'm just hoping to limp through the smog test.

[abscate]

You need cold start cycles to run the SAS test. You can also install the diode , and leave all the sAS parts on to pass the visual, to pass this test

[wrybread]

Thanks for that. I have a diode on the way just in case I don't pass the SAS. I'm hoping that code getting thrown was a fluke. I hotwired the SAS pump and it's working fine, so hopefully it won't come to drastic measures, but it's sure nice to have the option.