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Volkswagen OBD II Vr6 golf 00525 error code


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Last Post: Dec 20, 2013 9:42 AM Last Post By: Elbarto
Insamoufonyx

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Registered: 01/10/13
Vr6 golf 00525 error code
Posted: Jan 10, 2013 5:54 PM
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Hi all, I've got a mk3 golf vr6 and I'm getting error code 00525 - oxygen sensor short to ground.
I've replaced the sensor but still getting a code.

I've also checked the measuring blocks and the sensor voltage shows around 0.550v when first started and the gradually but very quickly (less than 30 seconds) drops to 0v and stays there. Once it's hit 0v it flags the 00525 error code again.

Can provide vagcom logs.

Any help appreciated :)
tcovenant2000

Posts: 1,775
Registered: 12/09/03
Re: Vr6 golf 00525 error code
Posted: Jan 10, 2013 7:25 PM   in response to: Insamoufonyx in response to: Insamoufonyx
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This is almost certainly a bad O2 sensor. It's crapping out when hot. That's very common.
You can tell for sure by disconnecting the O2 sensor and trying the test again (reading the voltage from the measuring block). If the voltage stays around .5V then you'll know the O2 sensor is bad. If it drops out anyway, further tests are indicated but check the wiring and consider the possibility that the ECU may be bad.

Thomas
Insamoufonyx

Posts: 13
Registered: 01/10/13
Re: Vr6 golf 00525 error code
Posted: Jan 11, 2013 3:42 AM   in response to: tcovenant2000 in response to: tcovenant2000
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Would have thought a brand new O2 sensor being bad was pretty unusual?

Im going to try what you sujested as well and see ive also had a look at a wiring diagram and going to try some checks for a short to earth.

i also noted on the fusebox and relay layouts ive looked at it states theres a relay in position 13 for the heating part of the O2 sensor, however when having a look on my car there isnt one in that position? could this be the problem that someone has removed the relay for whatever reason?

Cheers
Insamoufonyx

Posts: 13
Registered: 01/10/13
Re: Vr6 golf 00525 error code
Posted: Jan 11, 2013 6:02 AM   in response to: tcovenant2000 in response to: tcovenant2000
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Hi again,

ive done some checks on the wiring to see if its all functional as expected and here are my results:

Wiring Harness:

Pin 4 is down to earth
Pin 3 is down to earth

Pin 3 to Pin 4 is loop with 46300ohms resistance when cold.

Pin 3 to Pin 4 reads 0.445v on ignition and engine running.

On the Sensor

Pin 3 is down to earth.

To me the fact that Pin 4 and Pin 3 on the engine harness are both to earth sounds wrong or am i miss-understanding how the system works?

tcovenant2000

Posts: 1,775
Registered: 12/09/03
Re: Vr6 golf 00525 error code
Posted: Jan 12, 2013 1:56 PM   in response to: Insamoufonyx in response to: Insamoufonyx
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I'm not saying you're not missing a relay...however there is a separate code for open heater circuit which a missing relay ought to show, so that's a bit odd.
My son installed a brand new O2 sensor and in the process he damaged the connection at the top where the wire goes in (single wire style). His symptoms were similar in that the O2 sensor was showing as dead intermittently even though it was brand new. It's not likely, but not impossible that the O2 sensor is bad.
You are misunderstanding something.
If pin 3 reads 0 OHMS to ground and pin 4 reads 0 OHMS to ground there's no way that they could have 46000 OHMS between them.
If by "down to earth" you mean that they show 0 Volts then that's different. You'll need to measure resistance to ground on those pins.
Again, if the O2 sensor is disconnected and you put the negative lead of the meter on - of battery and measure the voltage at the pin (I don't have a wiring diagram, but it sounds like it's 3 or 4) and it is holding steady at .445 then it sounds like your O2 sensor is bad.
Try this: Read the measuring block with the O2 sensor connected and wait for it to drop to 0. Then disconnect the O2 sensor and if the voltage returns to around .5V and holds then the O2 sensor is likely bad.
Again, it could still be your ECU. The O2 sensor will act as though it isn't connected until it warms up, then it will act as if it's there. If the ECU is faulty it may show .5V or so until the O2 is operating.
Thomas
Insamoufonyx

Posts: 13
Registered: 01/10/13
Re: Vr6 golf 00525 error code
Posted: Jan 13, 2013 8:05 AM   in response to: tcovenant2000 in response to: tcovenant2000
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Right,

Ive replaced the o2 sensor again as most things were pointing to that, it seams to have partially solved the problem but not entirely, the new sensor reads fine most the the time but occasionally drops out but if i take the car back to idle and wait a minute it will come back and be fine again.

Could it be the case that my cars running so rich its tripping the lambda out? or is this not possible?

Cheers
tcovenant2000

Posts: 1,775
Registered: 12/09/03
Re: Vr6 golf 00525 error code
Posted: Jan 13, 2013 10:02 AM   in response to: Insamoufonyx in response to: Insamoufonyx
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It's not an issue of "tripping the lambda out". The O2 sensor senses the difference between ambient O2 and O2 in the exhaust. The lower the O2 in the exhaust the higher the voltage at the output of the sensor. So, no. Running too rich would cause a higher voltage.
However, if you're running lean (bad mix, low fuel pressure, vacuum leaks, etc) that would match your symptoms. The leaner the mix, the lower the O2 sensor voltage.
If it seems to work well at idle but gives you fits and drops out at higher RPMS then I'd suspect plugged fuel filter, weak fuel pump, bad injectors or an air leak on the air filter side of the throttle plate (as opposed to the manifold side which would cause probs at idle).
Insamoufonyx

Posts: 13
Registered: 01/10/13
Re: Vr6 golf 00525 error code
Posted: Jan 13, 2013 10:08 AM   in response to: tcovenant2000 in response to: tcovenant2000
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Attachment new lambda.csv (15.1 KB)
Very interesting reply thanks!

il have a look for any leaks as theres not many places there could be.

However when i stuck the car on my mates emisions tester it was reading 4.2% on the Co2 rather than 0.2% (required here) so i was under the impression that it was running rich? i also used to get a bit of popping and burbling from the exhaust when i had a Decat section in and i assumed this indicated it was running rich?

ive attached the .csv file of my vagcom log since fitting this new sensor, could you have a quick look and see if theres anything you notice thats odd?

Thanks

Edited by: Insamoufonyx on Jan 13, 2013 10:08 AM
tcovenant2000

Posts: 1,775
Registered: 12/09/03
Re: Vr6 golf 00525 error code
Posted: Jan 13, 2013 3:50 PM   in response to: Insamoufonyx in response to: Insamoufonyx
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Good info there! Thanks!

OK. A bit of school, if you don't mind.
When you burn fuel you are oxidizing chains of hydrocarbons. Hydrogen and Carbon molecules that combine with O2 to produce H2O and CO and CO2 and, by the way, heat which runs your engine.
As you move from too rich to lambda of 1 (ideal fuel/air ratio) to too lean CO2 starts low and CO is very high (due to insufficient Oxygen to convert all the Carbon into CO2 instead of CO). As you approach Lambda of 1, CO2 keeps rising and peaks at lambda of 1. CO, on the other hand, drops rapidly toward Lambda of 1 and as you get leaner it sort of flattens out.

You should check with your mate, again. Typical CO2% at lambda and too lean runs around 15-20%. That is what you SHOULD see in a proper engine.
However, typical CO is around .5% at Lambda and too lean. CO runs as high as 5% or so as the engine is running richer. Add a Catalytic converter to the engine and CO drops to well below .1%.
So I suspect that what you saw on the emissions machine is that the CO was running 4.7% and you were expecting .2%. Not CO2 which is what you said. I'm just trying to make sense of what you said here. If that's the case, I can only agree with you that you are running rich.
Having a cat and hearing popping noises can happen with too rich of a mix, but also with too lean of a mix. With too rich of a mix you don't burn all the fuel and it combusts in the cat. But with too lean of a mix you get misfires (lean misfire it's called) which means unburned fuel goes to the cat and combusts. So popping in the cat is meaningless for your purposes.

Question: In the .csv file it appears that the RPMS are all over the place. Were you revving the engine or is the idle loping like that?

Something is goofy, though. You can see that the LAMBDA % is moving off of 0%. 0% means that the ECU isn't enriching or leaning the mix. The mix is where it should be. You can see that the O2 output is dropping to 0V. The ECU responds by trying to rich the mix (Lambda % on your chart is increasing). The O2 sensor seems to respond by way overshooting (voltage above .5V). Then the Lambda % drops to zero or even negative (ECU stops leaning the mix). Then the O2 drops to 0V again and the cycle repeats. After a few tries, the ECU gives up (thus the long strings of 0% lambda and 0V on the O2). That's what's triggering your code. After a timed reset, the ECU again tries to rich the mix and the cycle repeats.

The fact that your emissions seems to indicate you are running too rich, but the O2 sensor says you are running really lean makes me think that you have problems in the exhaust system. Either the O2 sensor isn't threaded tightly or you have holes in the exhaust system that are allowing outside air to contact the O2 sensor. This would cause the engine to THINK it's really lean when it isn't. It's also possible that the O2 sensor is still just faulty. Swapping in another one would tell you for sure.

Thomas
tcovenant2000

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Registered: 12/09/03
Re: Vr6 golf 00525 error code
Posted: Jan 13, 2013 4:18 PM   in response to: tcovenant2000 in response to: tcovenant2000
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Just for your reference, here's a handy chart of emissions.

http://www.autoshop101.com/forms/h56.pdf

Thomas
Insamoufonyx

Posts: 13
Registered: 01/10/13
Re: Vr6 golf 00525 error code
Posted: Jan 13, 2013 6:51 PM   in response to: tcovenant2000 in response to: tcovenant2000
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Hi Thomas i appreciate the time your putting into you replies and im more than open to a bit of teaching!

Also my appologies i did infact mean CO not CO2.

In the during the logging of the .csv i was doing a short local drive. idle seams fine at 680-720rpm, everything above that was either a blip of the throttle at stand still, or me actually driving along.

If it would make the information clearer i will do a idle only log tomorrow. Is there any other measuring blocks that could help understand the issues?

As for leaks in the exhaust i will have a good look tomorrow, the lambda is clamped down tight to the crushing seal and the joint between the manifold and cat section is sealed, i will take a look at the manifold flange on the back of the head and theres a couple of blanks in the manifold i will tighten but to be honest it doesn't sound to be leaking from anywhere.

i would also be doubtful that the o2 sensor is faulty, i have had similar issues with 3 separate sensors now.

The only thing that has come to mind is that the o2 sensor earths through its body and through the exhaust by contact yes? when i was fitting the lambda today i noted that the top face of the threaded boss for the o2 sensor was covered in rust/dirt. im wondering if this poor earth connection could be causing issues? i don't really want to remove the sensor again unless i really have too, its a pain to do especially at this time of year and the thread on the cat section is a bit ropey and i don't want to make it any worse.

Thanks, Rob.
tcovenant2000

Posts: 1,775
Registered: 12/09/03
Re: Vr6 golf 00525 error code
Posted: Jan 13, 2013 8:40 PM   in response to: Insamoufonyx in response to: Insamoufonyx
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It's good to know that you were playing with the throttle and driving around a bit. I don't think you'll gain anything by trying to just idle for a long period while recording. In these instances the driving around data is more significant. You do have some periods of idle in your data already and it doesn't seem to matter if you're driving around or idling. Something is weird there.
This could, indeed be a grounding issue. One thing you can do is simple. If you have jumper cables try attaching the jumper cable to the battery - post and the other end of the cable to bare metal on the engine and see if it makes any difference. It isn't uncommon in these cars to have engine to battery ground issues and the jumper cable will certainly answer that. Just make sure you have a good, strong, clean connection at both ends.
If it doesn't seem to make a difference, you can try putting the jumper cable straight onto the O2 sensor at one end and battery - post at the other and again see if it makes any difference. If either of these things seems to help then some work is called for...either ensuring the ground from engine to battery or ensuring that the O2 sensor is making a solid connection to ground.
Do you have the 4 wire or the 5 wire sensor?

Thomas
Insamoufonyx

Posts: 13
Registered: 01/10/13
Re: Vr6 golf 00525 error code
Posted: Jan 14, 2013 4:33 AM   in response to: tcovenant2000 in response to: tcovenant2000
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ive got a set of good jump leads so i will give that a try earthing the engine to the battery later today, i think earthing directly to the lambda probe could be a bit more challenging.

the sensor is a 4 wire.

Thanks.
tcovenant2000

Posts: 1,775
Registered: 12/09/03
Re: Vr6 golf 00525 error code
Posted: Jan 14, 2013 10:13 PM   in response to: Insamoufonyx in response to: Insamoufonyx
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Yes. The 4 wire ones consist of 2 heater wires (that have nothing to do with the O2 sensor output, they just keep it warm!) and 2 wires that are both carrying signal. It's known as a "differential output". I think the auto industry realized their mistake with these, because the 5 wire sensors add a shield wire that goes to ground.
Yes, getting a connection with a jumper cable onto the O2 sensor is going to be fun. But if you're so inclined they do make jumper cables with angled ends.
I was only suggesting jumper cables because they are strong and it's easy to wiggle them around and ensure a good, solid connection. If you can think of some other way to ensure a good O2 sensor to battery negative terminal connection, try it!

Good luck! Let me know what happens.

Thomas
Insamoufonyx

Posts: 13
Registered: 01/10/13
Re: Vr6 golf 00525 error code
Posted: Jan 15, 2013 1:51 PM   in response to: tcovenant2000 in response to: tcovenant2000
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Attachment Log1501.xlsx (78.1 KB)
Hi Thomas,

Im just on the way out the door so i will make this quick,

I tried earthing the engine to chassis again today and it didn't seam to have any effect.

i havent had chance to try and earth the lambda directly yet but hopefully will tomorrow.

how ever i did carry out a idle log today and gave more successful results.

please see attached.

Cheers
tcovenant2000

Posts: 1,775
Registered: 12/09/03
Re: Vr6 golf 00525 error code
Posted: Jan 15, 2013 10:30 PM   in response to: Insamoufonyx in response to: Insamoufonyx
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Wow...that's more consistent.
All I can say it that it appears your o2 sensor believes you are running lean. When the lambda % increases (enriching the mix), the voltage comes up off of zero. That's consistent with the exhaust gas O2 content dropping down.
Ideal fuel/air ratio is an O2 output around .5V.
The really strange thing here is that your O2 sensor can't seem to produce anything other than 0 or .5. As the fuel mix is enriched the O2 still reads 0 then suddenly leaps up to .5V or more. Bizarre.

Thomas
Insamoufonyx

Posts: 13
Registered: 01/10/13
Re: Vr6 golf 00525 error code
Posted: Jan 16, 2013 4:21 AM   in response to: tcovenant2000 in response to: tcovenant2000
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Had another twiddle on the way out yesterday and i found that one of the manifold bolts were loose so i retightened that. This is making me wonder if i did infact have a airleak and the exhaust was bringing in clean air giving the car the impression it was lean, however i am supprised i hadn't noticed any blowing from the manifold if it was leaking.

I havent had a chance to do any logging since but i should be able to today. im also going to carry out some resistance checks from earth to then engine, exhaust and some other points just to ensure ive closed out the posibility of bad grounds. I belive anything reading above 0.5ohm would indicate a bad earth?

Cheers, Rob.

EDIT: The more i think about this the more i think it could have been the manifold causing a leak into the exhaust. Looking forward to doing some logging now.

Edited by: Insamoufonyx on Jan 16, 2013 9:22 AM
tcovenant2000

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Re: Vr6 golf 00525 error code
Posted: Jan 16, 2013 10:13 PM   in response to: Insamoufonyx in response to: Insamoufonyx
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Exhaust leak is really what I've been thinking. Makes the most sense. I look forward to the next log!

Thomas
Insamoufonyx

Posts: 13
Registered: 01/10/13
Re: Vr6 golf 00525 error code
Posted: Jan 24, 2013 5:59 PM   in response to: tcovenant2000 in response to: tcovenant2000
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Hi again Thomas,

Right, ive been a bit quiet as ive had a busy week or so.

Ive now replaced the lambda again and it's solved part of the problem but i seam to have uncovered a new problem.

I believe there is a wiring fault somewhere or my ECU is kaput!

i was doing some checks tonight as my lambda reads an almost constant 0.345v.

I "back probed" pins 3 and 4 on the lambda wiring while it was connected and the engine running.

The readings on my voltmeter were around 0.660v where as vagcom was reading 0.345v. So somewhere im loosing 0.2-0.3v so this says to me a wiring fault?

I tested the lambda plug pins to earth first with the ECU conected and got the following results:

Lambda Pin 4 To earth - 46k ohms
Lambda Pin 3 to earth - 289 ohms

Then carried out these checks again with the ECU disconected and got the following results

Lambda Pin 4 To earth - Open Circuit
Lambda Pin 3 to earth - Open Circuit

I also did some functional checks on the wiring back to ECU.

All wires from the lambda that go back to the ECU had a resistance below 0.5ohms (good results)

However when i checked the ECU pins that should be to earth i uncovered the following:

ECU Pin 56 to earth - High resistance
ECU Pin 7 to earth - Open Circuit
ECU Pin 1 to earth - below 0.5ohms (good)

Does this sound normal?

im going to "back probe" the return wires at the ECU to see if its still reading the same as right next to the probe tomorrow. That should tell me if its the wiring back from the lambda to the ECU.

Im still not going to know if its internal to the ECU or if the ECU isnt getting a good earth or live?

Cheers

tcovenant2000

Posts: 1,775
Registered: 12/09/03
Re: Vr6 golf 00525 error code
Posted: Jan 24, 2013 11:14 PM   in response to: Insamoufonyx in response to: Insamoufonyx
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Reading the ohms to earth on pins that are not supposed to be earthed is basically meaningless. You are pretty much measuring the resistance of an input circuit. The wire tests are good and seem to be fine. I was telling you before this might be an ECU problem based on the idea that the O2 output seems to leap from 0 to .6V or more without really ever going in between (there were some in-between numbers, but likely they are the result of averaging within the ECU).

Here's a simple test. Disconnect the plug to the Lambda sensor. Locate the two that aren't the heater wires. Short them both to earth. Run the car and check the voltage. This should cause the ECU to see 0V always and try to rich the mix over and over again, similar to what you were seeing before.
Next, connect a "D" cell battery (I assume you are in England or Australia or someplace where they speak English instead of American, so not sure what that battery might be called. It's a 1.5V cell, the larger size) across the wires. It can't hurt the ECU to get it backward, so feel free to connect it either way. It might be easiest to earth one of the wires, connect the other to + on the cell and then earth the - on the cell. Then check the voltage using the software. If it's always 0 or negative, spin the cell around the other way and try again. You should be able to read a constant 1.5V (may not be a full on 1.5V due to limitations in the ECU, but should read over a volt). It should never vary. During this time the ECU should be trying to lean the mix as much as it can, so the engine may struggle with running. I don't know if you can read the voltage with the software while the engine is off. But since the Lambda is a voltage output device and so is the battery this test should decide once and for all if the ECU is working.

Thomas

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