Clearing the Engine Management Light..

[jb0o]

How is this done?

I recently replaced the Cat Convertor on the A3 when a rattle noise appeared, note that at the time of the fault there was no Engline light on the dash.

The other day the engine management light came on and I got worried. I scanned the car expecting to find a new fault but I only found the Catalytic fault...(must have forgottent to clear it previously) so I clicked on 'Clear DTCs' and the Engine Managemt light is still on and when I scan the car the fault still pops up..

Any ideas? I didn't even think a faulty Cat would cause the engine management light to come on, but there is no other recorded fault..

Thanks

 

[bearthebruce]

if there is a leak in the exhaust, a code could be set. Without telling us the code information, it's really hard to guess what problem may still exist. Sure you got the right CAT? Did the Oxygen sensor get damaged during the install? Did the oxy sensor's wiring get damaged.

Post up the scan data. That will help us to help you.

 

[NHN]

Yes I would of said the sensor would be the 1st thing to check & if its plugged in mate for a start, as Bruce says a scan would help mate.

 

[jb0o]

Thanks for the replies guys and sorry for my late reply, been really busy the past week.

Heres the scan:

1 Fault Found:
16804 - Catalyst System; Bank 1: Efficiency Below Threshold
P0420 - 002 - Lower Limit Exceeded - MIL ON
Readiness: 0000 0000

And where could I check that the sensor is plugged in? Is it near the Cat?

Thanks again,

 

[NHN]

Sen Khufu a PM as he has this engine & I'm sure he could advise where & if there is a sensor on the pipe as he has ramps etc to check, I'm sure he wouldnt mind.

 

[bearthebruce]

There is a sensor before the cat and one behind the cat. Both can be monitored in measuring blocks - around group 032. The efficiency error usually means that the sensors are working but they are out of proportion to what is expected. As a result, more times than not, you have a leak in the system.

If a sensor were unplugged, then the heater circuit for the sensor would be barking about a fault in the heater circuit. While you should check that the wiring is not plugged in, I suspect you have a different problem that will not be solved by the sensors. Look for an intake leak after the MAF. Could be vacuum lines or others.

 

[Khufu]

Sen Khufu a PM as he has this engine & I'm sure he could advise where & if there is a sensor on the pipe as he has ramps etc to check, I'm sure he wouldnt mind.

I have the 2.0 FSi. IIRC when I looked my car has 6 sensors!

 

[bearthebruce]

Color me confused. You have 6 oxygen sensors in your exhaust? What do all of them do?

Documentation we have shows, one CAT, two sensors. One sensor before the CAT, one after. Take a look at this picture: http://i.imgur.com/qiRxRl.gif
The sensors are B1S1 - item 22; and B1S2 - item 3. Where are the other 4 sensors?

This fault code, as said, usually will occur when the two sensors are not in proportion to one another as they should be. Most often it is caused by a leak - not by a bad sensor.

 

[jb0o]

Thanks for the reply again guys.

Getting quite annoying this as the Cat was only fitted 4 weeks ago.

This may be a stupid question but how could I find the leak, suppose there is one?

 

[bearthebruce]

If replacing the CAT was the only thing done, I'd start looking around the job that was done to fit the CAT. If you can't find anything there, start looking at the plastic hoses and vacuum lines around the engine.

One last question: was the replacement CAT a OEM CAT or a less expensive aftermarket one? There have been reports in the US that some aftermarket CATs are not up to snuff. Just thinking about your problems.

Did you ever look at the output of the sensors using the measuring blocks?

 

[jb0o]

This is the Cat I got from Online Automotive: http://onlineautomotive.co.uk/Products.aspx?ProductCode=EX311824

I'll have a look at the blocks now..

 

[jb0o]

Have just looked at the Meas. Blocks of 032 and it showed the following:

0.8% 8.2%
Lambda Lambda

 

[Ads]

I had a similar problem when I had a cat changed. It wasn't on my A3 but still the same problem.

Kwikfit did the work using one of their parts (never again!!). Straight away engine management/cat faults appeared.
They claimed it was down to a leak and tried everything to put it right.... i.e. using LOADS of sealant around all joins throughout exhaust, changed sensors, removed and refitted entire exhaust.
Nothing cured the problem.

In the end I demanded they source a new cat from different manufacturer. They fitted it and problem was solved. No more engine management/cat faults.


Sometimes these non OEM parts just don't do the job. And I have always found exhausts are one of the worst for this. I've had numerous problems with them on numerous cars.

 

[bearthebruce]

I'm with you on the CAT - How can a $300ish CAT be the same as the $800ish CAT? I don't think that the OEM rips you off by more than twice. I think the inexpensive parts drop the platinum required to fire the CAT properly and do the job intended.

Only two readings were reported for the O2 sensors. If these were block 1 and block 2, then these only reported the Bank 1 Sensor 1 readings at idle and at partial load. We need to see all 4 readings because S2 determines the efficiency of the CAT. If you have no readings for sensor 2, then we can go after the wiring to the sensor as the problem. So, Group 032, you should have B1S1 @ Idle, B1S1 @ Partial Load, B1S2 @ Idle, B1S2 @Partial Load - those are the 4 blocks in that group. Further, the reading on B1S1 should be higher than the reading on B1S2. For more information on CAT efficiency - not just VW specific - see this page: http://www.autoshop101.com/forms/h64.pdf

 

[jb0o]

Thanks for the help Bruce,

I've checked group 032 again and all it shows is this:

I'm assuming its the 01-Engine controller

 

[bearthebruce]

Yes - 01 Engine. I'm going to be out of town for several days so I won't be able to do much more on this. Can you get me the engine code? I want to try to look up some tech data on your engine if i can. Also, what version VAG-COM? Are you running a full version? If not, can you find someone with VCDS 908 to take a look at the measuring blocks? I'm wondering if there was an issue in the label files you have for this module that may have been corrected in a subsequent release.

 

[jb0o]

Yes - 01 Engine. I'm going to be out of town for several days so I won't be able to do much more on this. Can you get me the engine code? I want to try to look up some tech data on your engine if i can. Also, what version VAG-COM? Are you running a full version? If not, can you find someone with VCDS 908 to take a look at the measuring blocks? I'm wondering if there was an issue in the label files you have for this module that may have been corrected in a subsequent release.

I was thinking this also, but I also flicked through all of the blocks available and didnt find any labels labeled "B1S1 @ Idle" etc..

Version is 704.1, was passed down from my brother. It is the full version (the about button verifies that)..

Where could I find the engine code? Would it be unfer the advanced ID of the engine controller?

 

[jb0o]

Problem sorted Thanks for the help chaps

 

[NHN]

Whats slightly irritating is when people have a problem & ask for help & help is given freely, they manage to resolve the problem, but they never update the thread with the solution overall, maybe it would be prudent for you to do this as too many people fail to update the threadwwith there fix/es & it doesnt help anyone in the end.

Also 704.1, is it registered with RT, sounds like its a counterfeit to me as it would of updated to 908 by now.

 

[Khufu]

My car has twin downpipe with twin cats. There were 3 sensors on each exhaust, one up near the manifold, one before the cat and one after. I though it odd too, no idea what the two up at the manifold do???

Looked at your pic Bruce, that's off a car with Turbo - over the pond here we have 2.0 Fsi without a turbo LOL