Readyness State

Hi, Can anyone help me with this? I have had missfire problems on cyl 3 and 4 on my MY01 XC70 AWD. Before maintenance I read and cleared the codes - the readiness code was OK. Now post maintenance the engine will not start but tries to do so. However the state of the readyness code has changed. This seems to be associated with an O2 sensor problem. My engine is the B5244T3. I understand this version has two O2 sensors. How do I set about diagnosing this problem and how do I access both sensors? Do I need any special tools? Any help is very much appreciated.

Is this the same thing as your previous thread? Were you not able to start the engine since this earlier thread?

https://www.volvoxc.com/forums/showt...ing-at-low-RPM

If so, I'd recommend not starting a new thread. It's the same problem.

I'm not sure what you mean by the "readiness code." Maybe it's a difference between the USA OBDII system and rest of world. In the USA there are several emissions related readiness monitors where the car must perform and pass diagnostic checks of various emissions related systems before the readiness monitor is properly set to a "pass" setting. In some states, if not enough monitors are set to "Pass," the vehicle will fail inspection. So, i'm not sure what this one readiness setting that you are talking about is.

I'd refer you back to Astro14's post in your earlier thread encouraging you to check fuel, compression, spark, and timing.

I thought this was a pretty good youtube video series on diagnosing a no-start condition. This is the link to video #1. There are 2 more. Could be helpful.

https://www.youtube.com/watch?v=LuRI8bjjNho

Brett

Hi yes, All points covered by Astro check out: plenty of fuel pressure but I was dismayed to see debris in the fuel I colleted from the fuelrail via the shrader valve (new fuel filter fitted a year ago but car sat idle mostly since due to Cov2- lockdowns here) Coils and plugs are new; Compression test = Ok; Oil is new; Coolant is new also chaned out coolant sensor and thermostat; MAF sensor and plenum chamber sensors good; new TCV valve and hoses - silicone -all electrical connections cleaned on engine harnes. The "readiness state" is in Volvo Vida Fault checking section, on selecting specific fault it comes up as oxygen sensor. Car is up on jackstands if it is dry tomorrow, as forcast I will be chasing the at area. Engine cranck fine and is close to starting. Off to get the battery out to fully charge again overnight - spent agood hour with ignition on using Vida DiCE today. Thanks for YouTube link that's a magnificent aid!

If you're seeing debris in the fuel from the fuel rail I would suspect you might have clogged fuel injector filters. These filters are small (see photo) and any amount of debris seen in the fuel could clogged them up rather quickly. You could pull the injectors and check the filters or do a basic type flow check. The O2 readiness shouldn't contribute to your no start condition as the O2 sensor is open loop when first starting a cold car. Debris in the fuel and reaching the injector fuel rail needs to be understood and dealt with.


simple test for injector flow check and be careful with this type of testing
https://www.youtube.com/watch?v=ImnIw3lQOnA

Does it start with external fuel, i.e. starter fluid delivered into the intake? If so, then it's a fuel problem, despite the fact that you have fuel pressure. Could be clogged fuel injectors as suggested by First Volvo or just poorly operating injectors. As I recall, you had a sudden stall. (If this was all in one thread, I would go to the top of the thread and confirm that was the case, but I can't since this is now in a second disconnected thread, and I'm not inclined to go hunting around and find your initial thread.) A sudden stall implies a sudden event. Clogging of injectors or poorly operating injectors isn't typically something that is sudden. I would expect a slow decline in performance.

Spray some fuel into the intake and see if it fires up. Very simple test to determine if the problem is fuel.

Coils and plugs are new, but that doesn't mean that the spark plugs are firing. Put a spark tester in each coil and see if there is spark.

Brett