O2 sensor for B5252 10valve fenix 5.2
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O2 sensor for B5252 10valve fenix 5.2
I am looking for details on how to test the upstream ( only1 ) O2 sensor on my 98 850 ( Canadian delivery. NOT 20 valve )
the b5252 with fenix 5.2 was delivered to non-US markets
Any help would be appreciated.
Currently the lambda light comes on about 30 seconds after start up.
Replacement (non OEM) sensors have not helped
12 months ago , if I turned the key to pos II, started the heater fan and then started the engine the lambda light stayed off
Possibly an electrical issue ?
Car runs ok with lambda light on.
the b5252 with fenix 5.2 was delivered to non-US markets
Any help would be appreciated.
Currently the lambda light comes on about 30 seconds after start up.
Replacement (non OEM) sensors have not helped
12 months ago , if I turned the key to pos II, started the heater fan and then started the engine the lambda light stayed off
Possibly an electrical issue ?
Car runs ok with lambda light on.
Senior Member
Joined: May 2012
Posts: 1,988
Likes: 52
From: Kingsport, TN
Well, you could backprobe anything there and just look at the voltage. That won't tell you what the ECM is thinking, but it could give you an idea if you have wiring issues.
If you've had the same problem with more than one sensor, you might also question whether the car is running hopelessly rich or hopelessly lean for some totally different reason. The car doesn't know which sensor to disbelieve, and the lamda light covers that whole area. The MAF has to be accurate and then fuel pressure needs to be accurate and all the spark plugs need to fire, and then it should all just work out such that the o2 sensors appear to work.
I trust this is common knowledge, but there are two wires down there that generate, when the engine is hot and the sensor is hot, about 500 millivolts (half a volt) between those two wires. It produces its own voltage and there's no "signal" power going there. The engine is supposed to vary the mixture to get the sensor to wander around a bit up to 800 mV and down to 300 mV. There are also going to be two wires down there that operate a heater. Naturally you'd have power going to this heater and a ground wire coming from the heater to ground.
If you want to backprobe at the ECM you'll need a wiring diagram, and I don't have one for that car. Look here:
https://www.volvoclub.org.uk
They have an entire 850 service manual posted (look for that), but it is the US service docs unfortunately. There are some other docs here on the UK site which might relate to the 10 valve engine. I know that's what they got some years.
If you've had the same problem with more than one sensor, you might also question whether the car is running hopelessly rich or hopelessly lean for some totally different reason. The car doesn't know which sensor to disbelieve, and the lamda light covers that whole area. The MAF has to be accurate and then fuel pressure needs to be accurate and all the spark plugs need to fire, and then it should all just work out such that the o2 sensors appear to work.
I trust this is common knowledge, but there are two wires down there that generate, when the engine is hot and the sensor is hot, about 500 millivolts (half a volt) between those two wires. It produces its own voltage and there's no "signal" power going there. The engine is supposed to vary the mixture to get the sensor to wander around a bit up to 800 mV and down to 300 mV. There are also going to be two wires down there that operate a heater. Naturally you'd have power going to this heater and a ground wire coming from the heater to ground.
If you want to backprobe at the ECM you'll need a wiring diagram, and I don't have one for that car. Look here:
https://www.volvoclub.org.uk
They have an entire 850 service manual posted (look for that), but it is the US service docs unfortunately. There are some other docs here on the UK site which might relate to the 10 valve engine. I know that's what they got some years.
Last edited by firebirdparts; Jun 4, 2024 at 12:28 PM.
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