CEL - O2 sensor only (too rich) BEW

Hi there,
Recently fixed a turbo overboost issue (bad N75) and hoped it would take care of an O2 sensor too rich, but alas it has not. I seem to have steady vacuum, had a shop do a smoke test and also checked that vacuum stays in the system after engine shut down using the Mightyvac.

Is there a VCDS test or series of tests I can run since I have hold of a borrowed unit right now? I'd love to narrow this down more.


Address 01: Engine Labels: 038-906-016-BEW.lbl
Part No SW: 038 997 016 R HW: 028 101 114 6
Component: R4 1,9L EDC G000SG 0282
Revision: 12345678 Serial number: VWZ7Z0D9265339
Coding: 0150031
Shop #: WSC 23344 444 11345
VCID: 2D5F00AAB762D956E5-5178
1 Fault Found:
18628 - Oxygen (Lambda) Sensor B1 S1
P2196 - 000 - Signal too High (Rich) - Intermittent
Freeze Frame:
RPM: 1344 /min
Torque: 0.0 Nm
Speed: 34.0 km/h
(no units): 255.0
Temperature: 27.0∞C
Absolute Pres.: 1040.4 mbar
Voltage: 1.898 V
Lambda: 12.9 %
Readiness: 1 1 0 0 0

I replaced the O2 sensor a couple of months ago and the CEL stayed off for a couple of weeks, but then came back on. I've checked off replacing the O2 sensor because of that, but I guess it could be that I got a bad one. Ideas?

Where did you buy the replacement sensor?

Amazon.com

Bosch 17480

https://www.amazon.com/gp/product/B005ETESNW/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

dugslug said:

.
18628 - Oxygen (Lambda) Sensor B1 S1
P2196 - 000 - Signal too High (Rich) - Intermittent
Freeze Frame:
RPM: 1344 /min
Torque: 0.0 Nm
Speed: 34.0 km/h
Absolute Pres.: 1040.4 mbar
Voltage: 1.898 V
Lambda: 12.9 %
Readiness: 1 1 0 0 0

Click to expand...

I see a few things that stand out to me, the code appears to be thrown when de accelerating indicating injectors pushing more fuel than desired, or the turbo actuator is not leaning out the system like it should.

I’m reading up on the actuator system, I can’t remember if it has a relearn procedure or a “you must drive for x mileage until learned”

Can you clear the faults and post another freeze frame so we can see if the numbers/set conditions change.

The light has come on immediately upon an engine brake deceleration situation in the past, usually 5-20 miles after clearing the code. I just cleared the codes today and I'm driving tomorrow a good 100 miles so I'll post the results after that drive.

But yes, all the freeze frames I've looked at for this code have had 0.0 Nm of torque and usually the speed is highway speeds.

dugslug said:

The light has come on immediately upon an engine brake deceleration situation in the past, usually 5-20 miles after clearing the code. I just cleared the codes today and I'm driving tomorrow a good 100 miles so I'll post the results after that drive.
But yes, all the freeze frames I've looked at for this code have had 0.0 Nm of torque and usually the speed is highway speeds.

Click to expand...

Any aftermarket parts? Tune? EGR system all intact?

While you drive it would be a good idea to watch or log the EGR system since it comes into play at light or no throttle. You might have the egr valve sticking.

Then I would be watching MAF actual vs specific.

Anyone else know what this upstream O2 sensor controls? All i’ve Found is EGR valve function...

It indicates that the system is reading fuel during engine braking - and there should be none. It's usually the O2 sensor on these cars. If it's not the sensor - something is letting "fuel" into the engine. I'm wondering if engine oil - like excessive flow through the breather / bad turbo would read high enough to cause this? My 04 had the same problem, but was just the sensor.

Could the throttle position sensor be out of adjust and with the pedal up the sensor thinks it's still being pushed on?

Anyone know the relearn for it?

This is the place to start.

Meister Kraft said:

Any aftermarket parts? Tune? EGR system all intact?

While you drive it would be a good idea to watch or log the EGR system since it comes into play at light or no throttle. You might have the egr valve sticking.

Then I would be watching MAF actual vs specific.

Anyone else know what this upstream O2 sensor controls? All i’ve Found is EGR valve function...

Click to expand...

There is a lot of talk about fuel in this thread.

The O2 sensor doesn't read fuel, it detects oxygen. The BEW uses the O2 sensor to determine if the EGR is working. It's throwing the code 'rich' because on a long deceleration, the engine reduces/stops fueling, the EGR duty is going to increase to reduce oxygen going through the motor to reduce the NOx. The computer looks to the O2 sensor to see less oxygen in the stream due to increased EGR flows and thus confirming that the system is working.

It also looks at the MAF sensor to see a reduction in intake air volume as some has been replaced by increased flows through the EGR.

All is stock on this car. No EGR deletes or tunes.

I cleaned the EGR valve twice in this car's lifetime, once about 2 months ago. Actually, more like scraped out the build-up. It looked like the valve had been moving but I have not checked the movement. However, I've never cleaned out the egr cooler or intake manifold. If I have to do this I certainly will, but I'd rather not if I can determine that the EGR system is working.



How do you check MAF actual vs specific? I don't see that measuring block in VCDS.

Any other clues to assess if my EGR system is working correctly would be appreciated.

Thank you for your thoughts on this!

I am guessing at the VCDS operations to run because I could not find a specific MAF test to run. Here's what I have so far:


Above is the Basic Settings run of the EGR test, the car was running and VCDS turned the EGR off and on, which I could feel as it happened.

Then I did a driving at 55mph run logging the EGR specified vs EGR actual from the Measuring Blocks 003 in VCDS. At time 41.3 I let off the throttle and let the car engine brake. There is an obvious separation between the specified and actual at this point.
What does this mean? It seems like the EGR cycling done in the Basic Settings would indicate that things are fine, but the graph seems to say otherwise. Then again, I have really no idea what I'm looking at.

dugslug said:

Then I did a driving at 55mph run logging the EGR specified vs EGR actual from the Measuring Blocks 003 in VCDS. At time 41.3 I let off the throttle and let the car engine brake. There is an obvious separation between the specified and actual at this point.
What does this mean? It seems like the EGR cycling done in the Basic Settings would indicate that things are fine, but the graph seems to say otherwise. Then again, I have really no idea what I'm looking at.

Click to expand...

You can see the duty cycle flat line as well, meaning the system effectively just shut off the EGR. Differences in MAF readings spec. vs actual while in gear with the EGR commanded closed is not unusual. I wouldn't read too much into it.

If your car is smoking excessively, O2 sensors can go bad and no longer read due to that as well as soot builds up on the sensor.

Hey Matt,

I pulled this off one of my thumb drives for comparison. No faults in the system.

Graph from an 04 BEW







02-sensor testing (Incase you need it)
See post #10 - http://forums.tdiclub.com/showthread.php?t=150556

Matt, I think what you are saying is that my graphs don't show anything is wrong with the EGR system. Is that right?

So if that is true, in my process of figuring out why I get a O2 rich CEL I shouldn't worry about EGR. My turbo is all good as well (N75 was the problem on a fault that showed up along with O2 rich).

There is some blue smoke on startup, for about 2 seconds especially on colder mornings. Is that typical? And is that enough to make an O2 sensor go bad? This could be one reason why a new O2 sensor a couple of months ago didn't show any CEL for a solid month after the replacement.

Then again, the car has puffed that same cloud of blue smoke on startup since 80,000 miles when I got it. Seems like it would have done the same thing to the original O2 sensor.


Meister, I can't tell if you have an engine braking situation scenario in your plots. This is the only time I see my EGR actual deviate from the EGR specified.

My car runs excellent. Feels like it has all the power of when I first got it at 80,000 miles.
Any other thoughts before I go out and buy another O2 sensor to replace the one I put in a couple of months ago?

Thank you all for your ideas!!

dugslug said:

Meister, I can't tell if you have an engine braking situation scenario in your plots. This is the only time I see my EGR actual deviate from the EGR specified.

Click to expand...

The graph I have is with an automatic so I didn’t gear hang like a manual, the best comparison is at the start from zero to seven seconds. Around the same rpms as the first couple of freeze frames provided.

On the graph you posted the 40-48 sec marker stands out to me, actual vs spec has a lot of deviations from each other. 100 is the max and the graph shows around 300 at the 42 sec marker.

So we check the box that the EGR system functions ok

I think you you are getting extra air entering the engine after the MAF and before the 02, new 02 installed is faulty, or you have a wiring issue. This next part is all on you, it’s all visual.

Keep us posted

What’s the best way to find where air might be entering the system?

I will take the O2 connector apart underneath and clean the connection to make sure that’s good. And inspect the wire going back up top.

dugslug said:

What’s the best way to find where air might be entering the system?
I will take the O2 connector apart underneath and clean the connection to make sure that’s good. And inspect the wire going back up top.

Click to expand...

A smoke machine is the best, my personal unit is a redline smoke pro.

Brake clean will act like a fuel source, spray around the suspected area and wait 15 or so seconds before moving to the next location

http://forums.tdiclub.com/showthread.php?t=150556

Ok cool, I know someone with a smoke machine so I'll see if I can have him take a look at the intake system.
Meanwhile, I ran another log with some of the info from the 003, 010 and 033 measuring blocks together and came up with this graph. If someone could analyze it for anything that might make an O2 sensor unhappy please let me know!
If there's nothing amiss on the plot or isn't other scenarios I should run on the VCDS I'll assume air leak or bad O2 sensor.
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I don't wanna jack this thread, I also don't wanna start a new thread...So here it goes...
anyone here know if when tuning a BEW if there is any legit reason to keep the o2?

I have a bunch of parts and am about to have a custom made DP.
I want the best econ/ power and if keeping the 02 gives some econ ill keep the POS...

Thanks in Advance