[Ellie]

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,.

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

 

[VAGguy]

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

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.

 

[Ellie]

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.

 

[ylwagon]

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.

 

[Tobias]

RE: ABS - You can 1) Reset 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

 

[Ellie]

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.

 

[Ellie]

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?

 

[Tobias]

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.

Ellie:

When the ABS module is replaced, it needs to be re-coded to the ECU. After that, it requires an Adaption be run. This can be done with VCDS and some other apps that talk to the car. It cannot be done with regular ODBII scanners. You might want to have the programing checked.

You can learn more here, but the part numbers will be different: https://forums.ross-tech.com/index.php?threads/1714/

Also, the Secondary Air Pump that comes on when the car starts up, changes the sound of the exhaust until the cat comes up to temp. Makes the car just a little throatier until it shuts off. The combi valve works with the SAI to heat the cat.

 

[Ellie]

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

 

[Tobias]

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

 

[Ellie]

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.

 

[Ellie]

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,

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

 

[ylwagon]

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?

If those are the original O2 sensors, they are around 20 years old now, and maybe wearing out. Four of them at $110 and labor at $150 X how many hours will be expensive. For comparison, my Audi A4 V6 has similar warm-up codes, typically for bank 1 (driver's side) despite changing all O2 sensors just a couple of years ago. After doing so the car ran better and the mileage increased enough to notice, but I still get that insufficient flow code. The problem is that insufficient flow can result from other things, such as clogged SAI passages which are awfully difficult to fix.

My thinking is that you, being smarter than the average bear, should buy a basic OBD code reader, from Harbor Freight, AutoZone, online, etc. to post them as you already do but avoid trips to your mechanic. As to your O2 sensor with the heater fault, I might skip that since the insufficient flow codes are going to light the CEL anyway, and a faulty heater won't have any effect on how the car runs. The rough-running is more important to solve at this point.

I'm kind of in the same boat with my A4; it has over 275,000 miles and has been needing attention. It is now my backup car, but I like it enough to put up with occasional troubles.

 

[Ellie]

If those are the original O2 sensors, they are around 20 years old now, and maybe wearing out. Four of them at $110 and labor at $150 X how many hours will be expensive. For comparison, my Audi A4 V6 has similar warm-up codes, typically for bank 1 (driver's side) despite changing all O2 sensors just a couple of years ago. After doing so the car ran better and the mileage increased enough to notice, but I still get that insufficient flow code. The problem is that insufficient flow can result from other things, such as clogged SAI passages which are awfully difficult to fix.

My thinking is that you, being smarter than the average bear, should buy a basic OBD code reader, from Harbor Freight, AutoZone, online, etc. to post them as you already do but avoid trips to your mechanic. As to your O2 sensor with the heater fault, I might skip that since the insufficient flow codes are going to light the CEL anyway, and a faulty heater won't have any effect on how the car runs. The rough-running is more important to solve at this point.

I'm kind of in the same boat with my A4; it has over 275,000 miles and has been needing attention. It is now my backup car, but I like it enough to put up with occasional troubles.

Thank you so much ylwagon and my sincere apologies for a very late response. I do not receive notifications from Passat Forum like I used to and unless I log in, I will not see new responses such as yours. I've done what's possible to get the notifications, but thus far unsuccessful.

I logged in to provide an update and saw your very helpful note.

I texted all the posts-responses from you all to my VW mechanic as I always do and politely said that I'm providing this information to help him to help me as I believe knowledge will empower us to solve issues more successfully! He does appreciate information that I provide and always tells me I'm not his average customer and he appreciate smart customers who care about their cars. And I always tell him that everything I know I learned from you guys and from being a member of Passat Forum and plus my own relentless search on Google about my car's issues.

To make the long story short, I asked him before we proceed with 02 sensor replacement, can he run another scan to see what codes will pop up and he did. The 02 sensor code did not pop up but these two, which originally had popped, did:

P1411 = Secondary air injection system, bank 2 - insufficient flow detected.
Probable cause: Intake leak, hose(s) blocked / leaking, secondary air system valve / solenoid.

P1423 = Secondary air injection system, bank 1 - insufficient flow detected.
Probable cause: Intake leak, hose(s) blocked / leaking, secondary air system valve / solenoid

So, he did not change the 02 sensors, but spent about an hour and half trouble shooting, running tests, changed a ripped hose some where in my car (sorry, I can't remember exactly where), cleared some clogged hose by putting some solution in it, cleared the codes and said its fixed and when I asked what the cost, he said consider it my Christmas present to you, Ellie, since, last month you spent about $900 on your car at my shop. I thanked him and gave him $100, plus a nice bottle of wine and chocolates for Christmas. Since, he does not charge me when ever I go there when my engine light comes on and he scans it.

I'm grateful to all of you for making me smarter not just for my car, but in general, b/c there is no point of spending our hard earned $ on unnecessary things.

My car runs fine knock on the wood, while my car is old, but I'll continue to take care of it as much as possible, b/c it is not just my car, its also my best friend, it truly is.

I wish all of you a wonderful holiday season and hope Santa brings you lots of wonderful things.

Thank you so much again.
Ellie

 

[ylwagon]

You sound like the kind of friend people would be lucky to have. If you are ever down towards San Diego, we'll have a bottle of wine with your name on it.

Those two codes, 1411 and 1413 may have the same problem in common. To recap, the 'secondary air' is blown into the exhaust manifolds prior to going through the catalytic converters, to mix with any un-burned gasoline as a way to speed the working of those catalytic converters when cold. An electric blower about the same size as a hair dryer supplies this air through pipes to so-called "combi" valves, one at the back of each cylinder head of the engine. When you start the car and the engine's coolant temperature is low, the computer will turn on that blower, plus open a small valve that conducts intake manifold 'vacuum' to rubber diaphragms of the combi valves. Atmospheric pressure acting on the other side of the diaphragm then opens the valves, allowing the secondary air to flow past into the exhaust.

This action being accomplished is inferred by the response of the rear Oxygen sensors, which should show less Oxygen than the front sensors. If not correct, then either the O2 sensor isn't working properly, the catalytic converter is defective, or the secondary air isn't getting into the exhaust. When both sides of the engine have the same problem, I'd suspect the last reason.

 

[Ellie]

You sound like the kind of friend people would be lucky to have. If you are ever down towards San Diego, we'll have a bottle of wine with your name on it.

Those two codes, 1411 and 1413 may have the same problem in common. To recap, the 'secondary air' is blown into the exhaust manifolds prior to going through the catalytic converters, to mix with any un-burned gasoline as a way to speed the working of those catalytic converters when cold. An electric blower about the same size as a hair dryer supplies this air through pipes to so-called "combi" valves, one at the back of each cylinder head of the engine. When you start the car and the engine's coolant temperature is low, the computer will turn on that blower, plus open a small valve that conducts intake manifold 'vacuum' to rubber diaphragms of the combi valves. Atmospheric pressure acting on the other side of the diaphragm then opens the valves, allowing the secondary air to flow past into the exhaust.

This action being accomplished is inferred by the response of the rear Oxygen sensors, which should show less Oxygen than the front sensors. If not correct, then either the O2 sensor isn't working properly, the catalytic converter is defective, or the secondary air isn't getting into the exhaust. When both sides of the engine have the same problem, I'd suspect the last reason.

Thank you so much ylwagon! Greatly appreciate your kind words and your wine offer!

This information is very helpful and if my engine light came on again, will pass it to my VW mechanic. While reading your post, I remembered he did say some valves were not closing correctly, but he fixed them.

Thank you so much again,
Ellie