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Old 04-27-2019, 11:39 AM   #1
stashio
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Location: Lancashire, UK.
Posts: 22
Default Slightly uneven idle - lambda or something else?

Hi folks my 3.2 has an uneven idle, I hesitate to call it lumpy because it's really not that bad. It doesn't seem to effect running at all yet but I wonder if it's a sign of a failing lambda sensor or something else? I've given it a full service including plugs so that side of things should be fine.

I have two codes against the engine:
09769 - Linear Oxygen (Lambda) Sensor B2 S1 Pump Current Trim Circuit
P2629 - 004 - Open
Freeze Frame:
Fault Status: 01100100
Fault Priority: 0
Fault Frequency: 2
Reset counter: 255
Mileage: 84358 km
Time Indication: 0
Date: 2000.00.00
Time: 09:39:23

Freeze Frame:
RPM: 3137 /min
Load: 15.7 %
Speed: 64.0 km/h
Temperature: 84.0C
Temperature: 22.0C
Absolute Pres.: 960.0 mbar
Voltage: 13.462 V

008599 - Oxygen (Lambda) Sensor B2 S1
P2197 - 001 - Signal too Low (Lean)
Freeze Frame:
Fault Status: 01100001
Fault Priority: 0
Fault Frequency: 1
Reset counter: 255
Mileage: 84378 km
Time Indication: 0
Date: 2000.00.00
Time: 14:17:03

Freeze Frame:
RPM: 2211 /min
Load: 51.0 %
Speed: 63.0 km/h
Temperature: 87.0C
Temperature: 22.0C
Absolute Pres.: 960.0 mbar
Voltage: 13.589 V
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Old 04-27-2019, 11:42 AM   #2
stashio
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The second code says the sensor signal is too low (lean) but does that mean the sensor itself is faulty or that it's correctly reporting the car is running lean and there's a different issue?
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Old 04-27-2019, 03:55 PM   #3
voxmagna
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I haven't used my vcds on a gasolene engine yet. Lambda sensors depending on their type usually output a changing voltage and it's best to look at them graphically in realtime rather than get a snapshot of data. The general rule is if they are changing their voltage when you do things to change the idle, they are probably o.k. That said, lambda sensors can be damaged or killed by bad fuel. The fault codes seem real but I would have expected to see the MIL light on? Here's one link but suggest you Google the fault codes. Notice in the link it says it's a common mistake to simply replace the sensor.

https://www.yourmechanic.com/article...-brady-klopfer

The fault frequency seems low, but is this because that scan was taken after clearing any fault codes? I'm always cautious treating vcds scans as the first point for doing a lot of work or spending a lot of money and I would try and look at what they are doing in realtime when the engine is up to normal temperature.
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Old 04-29-2019, 09:58 AM   #4
stashio
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Thanks!

Well the engine light came on today for B2 S1, I know S1 is the pre-cat sensor but which side is bank 2? I think that would be passenger side (UK) i.e. around the airbox on the V6 is that correct?

Second question as there's a left and right version of the sensor does that mean left hand facing the engine from the front of the car? I'd guess it would be facing the same direction as the car (i.e. as my back was to the engine)? Probably a daft question but worth asking ha ha! Thanks again.

EDIT: I figured it out, basically the sides are as though you're sat in the drivers seat (i.e. the car's left or right because you're facing the same way as the car - makes sense). Bank 2 is the left (i.e. passenger side for RHD cars) and sensor 1 is pre-cat just behind the air box. I'm off to give EuroCarParts some more of my hard earned money!

Last edited by stashio; 04-29-2019 at 10:50 AM. Reason: Google
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Old 04-29-2019, 02:50 PM   #5
voxmagna
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I have the Tdi which is configured different. But if you disconnect one at the connector on the bulkhead clip one at a time, the MIL light will come on, but scan and see which one it tells you is really faulty or which one was good and is now faulty (The one you disconnected).

Great thing about vcds, if you are canny it's a brilliant tool. My thermal sensors from memory had different wire colors. The thermal sensors usually have 2 wires, whereas lambda sensors normally have 4 wires, which should narrow them down. Lambda sensors are an important compatible part and if I thought one was faulty, I would only replace it with a genuine W.W OE part.
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Old 05-03-2019, 04:25 PM   #6
stashio
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To wrap this one up the car threw an engine light, replaced the lamba and that solved the problem (touch wood)!

It's worth knowing the OEM lamba's are Bosch, I bought mine from eurocarparts for 80 so you get OEM without paying the dealer tax.

Cheers!
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Old 05-14-2019, 09:49 PM   #7
voxmagna
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What makes the sensors expensive is the OE V.W proprietary connector. When you look in a Bosch catalogue you will see a million all with diffferent connectors. But basically most are the same sensor using 4 wires and some with 6 wires.

That's why Bosch sell 'Universal' lambda sensors. It's pretty much the same sensor as all the others, but you have to splice it on to your old V.W connector. I've replaced 3 or 4 of these in different cars and at the last count the universal was around 25-30 each, but there's more chance of finding the universal cheaper than a specific brand.

Temperature sensors in the exhaust are a different story because they have to match the curve already programmed in the ECU and V.W use 2 different sensor technologies. MY07 use the older (expensive) platinum sensors and shouldn't go wrong. Later cars use a cheaper thermistor at the edge of their spec in the pre-cat hottest exhaust. Which is why they seem to fail a lot.
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