'97 Model 850 Oxygen Sensor Monitor Not Ready

[jpeisker]

Vehicle at issue is a 1997 Straight 850 in USA with 120K miles.

Problem is passing state inspection here in Texas where they recently changed the emissions law saying no-go if more than two ODB-II monitors are not ready. It's well-documented that the '96 and '97 850s have problems with monitors being ready, since the catalyst (C) and evap (E) monitors always reset when the ignition is turned on, meaning they won't be ready until a drive cycle is completed.

So I'm already handicapped with two not read(ie)s, meaning the state will allow no more, and I can't be sure an inspector will let me keep the engine running before he hooks up his tester even if I can get them to be ready after a complicated drive cycle. Besides these two monitors, the oxygen sensor monitor (O) is the only one I can't get ready, so I am looking for some tribal knowledge here. Dealer service department claims this is not documented and that they can only go by what their shop diagnostic tool tells them is wrong (in this case, nothing).

What does it take to get the oxygen sensor monitor ready on a 1997 model 850? The oxygen sensor heater monitor is ready and happy. No codes show up when scanned, so the O2 sensor may be OK. It's illogical but possible that the O2 sensor has to be good before the monitor can be ready. In which case, how do you know that the sensor is good if the monitor is not able to check for a fault? (chicken and egg scenario) Or are there simply some other conditions that have to be met for the O2 sensor monitor to be happy?

Should I just replace the front O2 sensor anyway? Hate to go to the expense and trouble of this, but if it's a good fix, then I will. I'd like a definitive answer to the readiness question, but I'd settle for a sure solution based on similar experience.

Thanks,
Jim

[Zimbo]

Are you checking readiness yourself? This is the first I've heard that evap and catalyst reset each time you start the car. That's certainly not the case for my 97 850 turbo.
Maybe it's different with turbo?
Once my monitors get to a state of readiness they stay there for me. Getting them there has been my headache.

-Rob

[MadeInJapan]

Issues with readiness none-the-less is a known issue with our cars and many testing stations actually hook up a smog reader to the tail pipe instead of go with the 02 code (at least in California, from what I've read). Check locally in your area, to see what flexibility they have with testing your car.

[jpeisker]

Zimbo, you're blessed not to have the same issue, since your '97 is a turbo. These readiness problems are reportedly documented in Volvo SB 2-23-0056 (although I can't find a copy directly) for '96 turbos and '96-'98 Volvos excluding turbo 850 (seems like these two overlap with the '96 turbo).

This service bulletin is referred to by numerous state and federal documents I've dug up on emissions testing and ODB-II. Most suggest that the evap and catalyst monitors reset themselves every engine cycle, and this seems to be true for my vehicle. A federal document (EPA420-R-01-015) with the friendly title of, "Performing Onboard Diagnostic System Checks as Part of a Vehicle Inspection and Maintenance Program" features this bit on Volvos in Appendix D:

1996 Volvo 850 Turbo - Vehicles will clear readiness at key-off. There is no reprogramming available for this line of vehicles. These vehicles should be scanned for MIL illumination without regard to readiness status. Volvo Technical Service Bulletin #SB 2-23-0056.

1996-98 Volvo vehicles (excluding 850 Turbo) - These vehicles may have a high degree of “Not Ready”for catalyst and evaporative monitors due to a “trip based” design. Volvo has provided driving cycles in its service information to allow monitors to operate. These vehicles should be treated as other non-problematic vehicles. Volvo Technical Service Bulletin #SB 2-23-0056.

MadeInJapan,
Until Sept. 2008 it was true in Texas that you could get away with a tailpipe emissions test (which is how I've escaped until this year). But state law now mandates that the vehicle cannot pass regardless of emissions quality if there are more than two monitors not ready. As I said, it appears that the catalyst and evap reset themselves everytime I turn on the engine, so if I just ignore these, I need to get that pesky O2 sensor monitor ready to keep me at my limit of two.

Anybody know the conditions for getting the O2 monitor ready?
Jim

[MadeInJapan]

Looks like you might be in for a swap unless you find that the problem with readiness is really leaking vacuum hose(s) or a MAF going bad...all of which can create the illusion that the front 02 is the culprit. Get all of those checked out before sinking the bucks.

[jpeisker]

Problem solved, hope I can explain it well....

Apparently the oxygen sensor monitor does not go ready until the catalyst sees a few successful cold starts with a properly functioning secondary air system (air pump). I infer this through a recent replacement of all my secondary air system parts. Until a few cold starts since replacing these parts, the O2 monitor would never be ready.

The air pump was tackled first because it was running intermittently (I would hear an occasional whine or squeal from it). It finally quit altogether and would not run on or off the vehicle. Unlike other people's experience, mine was not full of water, just dead. So I replaced it with an aftermarket Volvo replacement 1270558 (not the low-cost VW pump). When this pump runs it is relatively quiet and I can't hear it when the engine is running (some people have reported hearing the pump running).
The pump relay tested good on the bench but the dealer service shop claimed it was bad, so I replaced it anyway (could have been intermittent or weak under motor load).
After replacing these two parts I was hoping this would get the O2 monitor running again, but after a week of driving it was still unhappy.

Since the dealer shop diagnosed only the air pump and relay, I had not checked the air injection valve (AKA secondary air system (SAS) valve). Upon examination out of the vehicle, it was stuck in a slightly open position, letting just a little air by when I blew through it. After soaking in carb/throttle cleaner for a long time it would still not budge. So I got a replacement SAS valve and gasket. It was good to see that the new valve had the improved design, evidenced by a disk instead of cotter pin visible through the outlet port. This new valve opened and closed firmly when vacuum was applied or shut off. Lots of air would go through when open and you could feel and hear a solid "clunk" when the valve was opened and closed.

Put this on the car (unlike many people report, I had no trouble working the 10mm bolts with a 1/4" socket wrench, although I have a non-turbo model). and checked for vacuum control to the valve. Starting the car cold, the solenoid control valve opens about 30 sec. after turning on the engine. The vacuum was a bit weak (8-12" Hg), less than manifold pressure (20" Hg), and not enough vacuum to operate the valve (it would not "clunk"). So I followed the line back to the control solenoid valve and watched the vacuum jump around when I wiggled the black elbow at the end of the solenoid valve. Clearly there was a leak around there which was enough to keep the SAS valve from opening. Removed the solenoid valve and found the black plastic inlet/outlet ports loose so I applied high temp silicone gasket material all around it and let it cure for a few hours. Reinstalled and reconnected the lines and measured reliable, solid vacuum at the SAS valve and a good solid "clunk" when it operated.

While I was checking vacuum in this line I pulled the little black/white check valve between the intake manifold and the SAS solenoid valve. Found it to pull through both directions, so I replaced it as well (should pull vacuum only one direction). Not sure how important the check valve is or why it's even there but it must serve some functional or safety purpose.

After replacing/repairing all these secondary air components and driving around for a few days, suddenly the O2 sensor monitor got ready and I headed straight for a state inspection place to get my sticker. As expected, the Catalyst and Evap monitors are never ready but Texas allows two (maybe because of '96 and '97 Volvo 850s !) so it passed and I was very happy. The inspection guy told me that because of this issue he's seen some 850 customers give up on their cars and sell them out of state because they can't pass inspection here. As an engineer I'm a little more determined to solve the problem and can't really afford a new car right now anyway. The dealer service departments aren't all that helpful either, so it's no wonder. This has been a seven week ordeal: multiple trips to the dealer, new battery (which resets the computer), multiple component diagnosis and replacement myself (some of which reset the computer), lots of waiting and drive cycles to see if the computer is happy, one warning from a state trooper for attempting to follow the "official" drive cycle on a freeway, and lots of head scratching and research all along the way.

One frustrating thing to note is that the computer did not set any trouble codes relative to the secondary air system. All those things wrong and it wouldn't give me the usual P0401 or anything else. I guess the SAS valve was open just enough and the pump worked just often enough to make the computer happy about their behavior, but not satisfy the O2 monitor.

So I have two things to summarize here-- 1) O2 monitor readiness seems to depend on multiple cold starts with properly operating secondary air system. 2) Secondary air system can have multiple issues. In my case, I ended up replacing or repairing all five functional components because they were all truly defective (OK, the pump relay was only suspect). Hope this helps somebody else with similar problems.
Jim

[turbotim2]

Thanks for your diagnosis, I am sure this will help many out there!

[MrAl]

Hello,

I recently found this quote in this thread:

START QUOTE
1996-98 Volvo vehicles (excluding 850 Turbo) - These vehicles may have a high
degree of “Not Ready”for catalyst and evaporative monitors due to a
“trip based” design. Volvo has provided driving cycles in its service information
to allow monitors to operate. These vehicles should be treated as other
non-problematic vehicles. Volvo Technical Service Bulletin #SB 2-23-0056.
END QUOTE

But i read elsewhere that there can be up to 2 monitors 'not ready'

So which is true?

Thanks.

[abscate]

The EPA says up to two monitors can be not ready. For a 1999 or earlier. Each state can choose to follow the EPA rule, or not. You have to confirm with your state.

[JRL]

2 not readies allowed all the way up to and through MY 2000, ESPECIALLY non turbos (Denso cars)