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Discussion Starter · #1 · (Edited)
Hi All,

it's me again and I need your expertise recommendation. My engine light came on the when my VW mechanic ran a scan, there was the P0155 and a handful more, please see image below,.

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Here is what i found online - 'P0155 is a very common OBDII code that occurs in the Volkswagen Passat. It is caused by a failure in one of the oxygen sensors heated elements, specifically bank 2 sensor 1' and I shared with my VW mechanic too.

He recommended just to change that instead of all the 02 sensors. He said the labor will be $150 (an hour) and part Bosch will be $110.

What do you guys think?

I'm not sure if this code represents upstream or downstream 02 sensor, so please educate me. Also is this on the driver side or the passenger side?

I think its downstream per my mechanic and I also found the part at Autozone, please tell me if its the right part (attached).

Also, please see the other codes and educate me about the solution/s.

Lastly, while my car is running fine, not sure if this is related to 02 sensor, hence the P0155 code, my car's MPG has gone down 21 and this happened right after the 02 sensor situation.

Thank you so much!
Ellie
 

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Discussion Starter · #3 ·
1. They'll need to scan the ABS for an additional fault code. That message is just alerting you that there is a stored code in the ABS module.
2. Secondary air injection codes (both sides, or Banks). Below is a schematic of the SAIP system on the V6. Since you have both codes, first places to look are where both can be affected at once. #7 hose below comes out of the pump and then connects to #10 which splits off to the combi valve on both banks. Leaks can happen there. Then you have #24A which is the vacuum line from the solenoid. If any part of that is ripped or broken, it will not allow the combi valves to open and let the air through. Finally, the solenoid itself and the supply vacuum line to it.
17831/P1423/005155 - Ross-Tech Wiki
17819/P1411/005137 - Ross-Tech Wiki
View attachment 107542

3. Sensor 1 no matter which side is the one closest to the engine . AKA Upstream. It measures the amount of oxygen in the exhaust stream and works with the ECU to make sure the air and fuel ratios are optimal for peak efficiency. That affects the fuel economy and running condition if it is not working properly. It can produce misfires if the aforementioned ratio is off enough.
Thank you so much VAGGuy! I will text this information to my VW mechanic and see what he says. It sounds to me he needs to do some trouble shooting instead of change the 02 sensors? Please tell me in simple language what should be done and thank you again.
 

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Discussion Starter · #6 ·
RE: ABS - You can 1) Rest the DTCs and see if it comes back. 2) Disconnect the battery overnight (forcing the computer to reboot). Make sure you have your radio code. 3) Clean your battery terminals, and clean any rust or grease off the grounding point for the ABS module. If it is the ABS module; in newer models, VW forces us to buy the Pump and Controller Assembly which can run $2000. I have no affiliation with the company in the link below, but other people have purchased rebuilt abs modules from them. One note about rebuilds. The more you pay, the longer the warranty, but the parts in the module are all the same quality.

ABS module repair rebuild service for 97 98 99 00 01 02 03 VW Volkswagen Passat | eBay amdata=enc%3AAQAHAAAAsCvh%2F6927kpEPlQxxEH66UbqfZmQPHj2Ug75yhQH4%2FFVMJc6UGUc8Y3XFPrEusKCJoJX5k6BZ3qK%2FxrLHvV66x%2FXIX6az4ib%2Blpz9fAaAKvE5icjgon0PakWWFXd5S3aEC9fmb0Wiy%2FnPB2sRsgTNztCQ4xFlpXwsZ59vXE7qE4F0znCKBNifZvpOj1iIS4CNedpenTSIWWHrVa7kscvn07rBDdhrEt8VASK7eTuqZzK%7Ctkp%3ABk9SR4aQ6f-TYQ
Thank you so much Tobias. The ABS module was changed at VW dealership and the light and blinking came on a week after that. This was a while ago, but I will provide this info., to my VW mechanic to address it.
 

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Discussion Starter · #7 ·
The P1411 and P1423 codes are really a concern only at smog-check time, otherwise they don't hurt the car.

Those insufficient-flow codes can also be due to a worn-out SAI (secondary air injection) blower/pump. It should turn on for perhaps a minute when the engine coolant is cold, its purpose is to blow additional air into the exhaust manifolds ahead of the catalytic converters, to get them working quicker after startup. The blower tends to be hard to hear when the engine is running, unless you are close to the passenger-side headlight, which is slightly above the SAI pump. They can go bad - I changed it on my Audi A4 within the last couple of years but it won't affect fuel economy or cause misfires. Your mechanic should be aware that if he finds a seized SAI pump (can be due to water accumulation) it may have blown the SAI fuse, and/or damaged the SAI relay.

As an aside, I've been doing routine maintenance on the A4, and found the SAI outlet hose loose where it plugs onto the pump (obviously my fault because I had done the previous work). Hopefully you have a simple issue like that.
Thank you so much ylwagon. This is very helpful. I'm putting together everyone's reply on a word doc., will print and give it to my VW mechanic. I've done this in the past when you all provided insights and he appreciated that. It will help him to help me.

Just so that I understand this correctly, should my mechanic change the 02 sensor or not? My apologies, I'm not clear. I understand per you reply that he should do some trouble shooting first before he changes the 02 sensor?
 

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Discussion Starter · #9 ·
Hi All,

Thank you so much for all the information you have provided, educational and very helpful. So, based on what you know, should I've my VM mechanic do these trouble shooting to see if any of the issues above present before change the 02 sensor?

My apologies, I'm not sure what needs to be done, so please feel free to advise. I'd like to avoid additional cost if possible, since I just spent nearly $900 to get the thermostat housing and bunch of other related things fixed.

Thank you again and wishing you all a delicious Thanksgiving and very thankful to be a member of this wonderful forum and super grateful for all of your help over the years.

Ellie
 

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Discussion Starter · #11 ·
Ellie:

The Secondary Air Injection system may have gotten bumped when the Thermostat housing was replaced. @VAGguy, I don't know the layout of this engine well enough to advise here. If during the thermostat service something was jarred, what should Ellie tell her mechanic to look for, and possibly apologize for missing?

Toby
Thank you so much for this information. While I greatly appreciate to have a VW mechanic with reasonable labor rate of $150 per hour, he is very knowledgeable too and a nice person too, always on pins and needles for his repairs on my car, b/c half of the time when he fixes something, other things gets messed up, which I had to pay for or he just makes a bandwidth repair instead fixing it correctly.

I've spent lots of time to see if I can find another mechanic, but unsuccessful.

So, its possible that per your assessment 'Secondary Air Injection system may have gotten bumped when the Thermostat housing was replaced.' And he always tell me my car is old,and these kinds of things can happen often. This is my third VW car and I drove each of them for 100s of miles and even when I bought a new car, there was always something to fix right away, so, I've decided to hang on to my 2003 Passat as much as possible, get the repairs done instead of buying another used Passat. My apologies for all the stories, but we live in a society that doing the /right thing' is not on everyone's agenda as much as I hope for it.
 

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Discussion Starter · #12 ·
Thank you so much for this information. While I greatly appreciate to have a VW mechanic with reasonable labor rate of $150 per hour, he is very knowledgeable too and a nice person too, always on pins and needles for his repairs on my car, b/c half of the time when he fixes something, other things gets messed up, which I had to pay for or he just makes a bandwidth repair instead fixing it correctly.

I've spent lots of time to see if I can find another mechanic, but unsuccessful.

So, its possible that per your assessment 'Secondary Air Injection system may have gotten bumped when the Thermostat housing was replaced.' And he always tell me my car is old,and these kinds of things can happen often. This is my third VW car and I drove each of them for 100s of miles and even when I bought a new car, there was always something to fix right away, so, I've decided to hang on to my 2003 Passat as much as possible, get the repairs done instead of buying another used Passat. My apologies for all the stories, but we live in a society that doing the /right thing' is not on everyone's agenda as much as I hope for it.
Here are the parts and labor for thermostat housing which was done a couple of weeks ago,

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My engine light came of a couple of days after the repairs and my car kind of runs rough now.
 
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