93 850 a/fs and code

whatthe · Post by **whatthe** » 04 Feb 2006, 11:49

One of my wifes friends was over yesterday and mentioned the check engine light was on in her 93 850 (no turbo 20 valve). She took it to a 'volvo place' and they told her it was 'o2 sensor code' and 'MAF code'. They reset the codes (supposedly 'cleaned' the sensor) and told her if the light came on again, she would have to replace both sensors despite the car driving and idling normal. The light came on again the next day for her.

While she was talking with my wife, I put my wideband on her car and took it for a quick spin (I have a portable system that attaches to exhaust tip). It was 14.7:1 while driving, and 13:1 WOT... at idle it was a slightly rich at 13:1-ish. Other than the idle, pretty normal. From the results, the car is safe as is, and I would not tell her to get new sensors until the current stuff is looked at a little closer.

I noticed the article about the worn connections, and I didn't take anything off the car to have a look yesterday. I have not worked on Volvos, and I did not know the procedure for resetting her light yesterday anyway. I did manage to check and get the 121 code though.

I was just wondering if anybody else has had problems with the 121 light, but no obvious problems with the running condition of the vehicle. I don't mind taking the sensor off for her and looking at them as well as the connections and stuff, but is there anything else that should be looked at?

Post by **MadeInJapan** » 04 Feb 2006, 13:15

1-2-1 on these systems is MAF signal absent or faulty. You may know of the fix for this already, but use some contact cleaner and push the sensor on the MAF housing and pull it off quickly. Do this about 15 times or so. Then use a plastic tie to cynch down the wire lead that sticks up on the connector to around the housing. Here is a write-up: http://www.volvospeed.com/Repair/maf_secure.php
If there is no signal from the MAF, the car will still run, though not at optimum levels. If it is running this way, of course the 02 sensors are going to give false and possibly problematic readings, setting a CEL. Therefore I would not assume that the 02 sensor is bad to begin with as the shop your friend took her 850 to did. If you get everything sorted out and you plug the MAF in and the car bucks and idles wildly or dies, then your MAF is truly bad and needs replacing. I would look for one at a junk yard to begin with if this is the case...these things are not cheap...close to $200...but www.fcpgroton.com is your friend's new friend, if this is the case. The MAF can be replaced in 10 minutes and only takes a screw driver. On the other hand the 02 sensor is a real pain and takes a special tool to do it right. If this is the case, do not get the one you have to splice wire in...get the one with the Volvo connectors already attached. fcpgroton has these too.
Regards,
MIJ

whatthe · Post by **whatthe** » 05 Feb 2006, 09:42

Thanks for the reply, I will try the fix for her when she comes by again. It drives fine, so I will assume the connection problem.

whatthe · Post by **whatthe** » 16 Feb 2006, 08:48

The connections didn't look too bad when I saw the car. I tried the 'fix' then looked at the codes (The codes this time were 1-2-1 and 2-3-1 (I think it was 231 not 232), and then reset the codes. After about 20 miles the light came back on though.

Apparently now, it is surging a bit at idle, up-down, up-down...

Is there a lambda adjustment on these cars (the code says something about lambda adjustment), and could that be causing hte problem?

She was going to buy a new MAF because the idle was worrying her. Is there something else to try first? I hate to have her spend the money for nothing.

Post by **MadeInJapan** » 17 Feb 2006, 18:33

I still think it's a MAF...and it's setting the secondary code. Depending on what is read from the MAF, the fuel mixture is adjusted by the ECU. It's not being properly adjusted and therefore the code. I may be wrong, so I hope someone else chimes in here...don't think it's a true O2 (oxygen....or lambda) code.

whatthe · Post by **whatthe** » 18 Feb 2006, 10:19

I think you are right. I checked the code yesterday for her and it was just the MAF by itself this time. Perhaps the maf was just giving the false readings at/near idle. The O2 was cycling fine and everything was fine at cruise, it was 14.7:1 as it should be.

Anyways, I had her grab a MAF and put that in. She said it drove better and I'm not sure if the light has come back on. So far, it looks to have been the problem. I would have thought the sensors would suffer a more complete failure.

Side question - is the block heater on the front or back of the block if there is one? She killed the battery in -30c trying to start it before we swapped the MAF, and we had to get it going in -20c last night... which it wasn't being very gracious with. I couldn't see a cord in the dark, so in the odd chance the cord was ripped off, should I look by the firewall side, or rad side?

Post by **MadeInJapan** » 18 Feb 2006, 12:14

I'm hoping the new MAF did the trick...where did you find a replacement? Dealer is expensive. About the block heater, recall campaign 79 deals with a replacement of them no matter what the miles or age. Don't know if she knows this...especially if it's out...but it was a fire hazard. Sorry but never used one, so I'm not sure of the location or where the wiring is, though always thought the wiing was behind or at least near the passenger side head light. Does it plug into a wall socket or is it interally fired up by the battery?