VW Beetle Forum banner
1 - 20 of 34 Posts

·
'02 Snap Orange 1.8T/5spd
Joined
·
152 Posts
Discussion Starter · #1 · (Edited)
2002 Beetle with 1.8T. I'm getting a CEL and codes for:

17608 Boost Pressure Control Valve (N249)
P1200-35-00 Mechanical Malfunction

16795 Secondary Air Injection System
P0411-35-00 Incorrect Flow Detected


I'm using the current version of VCDS, along with Bentley, but don't see the location or mention of N249 in 26-16 and subsequent pages, but have located it using Diagnostic Test Mode (it's on top of the valve cover, in the middle of the cover. It does click on and off, if I attach a hose to either of the ports, it will pass both vacuum or pressure (blowing or sucking on the hose with my mouth).

I have a functioning blower, both for the long run time on initial cold start, and for the shorter run times during monitoring at idle, as well as in Diagnostic Test Mode. I also have vacuum leaving the solenoid on the valve cover that's located in the corner, behind the oil filler cap.....which ultimately feeds the combi valve to open the valve.

I haven't removed the combi valve to check if it opens, but during the initial cold start blowing session, the idle speed is increased until the blower shuts off, and then idle drops down to normal.....but maybe combi valve allowing air into the exhaust wouldn't cause this.

Based on what I see in Bentley. there doesn't seem to be much to this system: The ECM switches a control relay near the brake booster. That relay triggers the vacuum solenoid on the valve cover to allow vacuum to get to the combi valve and open it, and the blow blows air (powered through that same relay?).

How does the ECU set a code for blower function?

Does the "Mechanical Malfunction of Boost Pressure Control Valve N249" mean it's probably gummed up inside (and therefore junk) and not allowing pressure or vacuum....or whatever it reads/delivers/allows to occur?
 

·
'02 Snap Orange 1.8T/5spd
Joined
·
152 Posts
Discussion Starter · #3 ·
I don't know how to make VCDS do a scan. Can you tell me what that is, what it shows, and how to do it.

The car also won't pass cat aging test, in set readiness codes. It shows a constant reading of .53 in window 3 during "test on" mode.
 

·
Registered
Joined
·
15,839 Posts
17608/P1200/004608 - Ross-Tech Wiki

16795/P0411/001041 - Ross-Tech Wiki

There are two solenoid valves located in the vacuum system (N112/N249), one enables the diverter valve to open (N249), typically when the engine is at idle or when changing gears to re-direct unused boost pressure, while the other (N112) allows the EGR, or combi valve, to open during cruising speed for increased fuel economy and lowered emissions.

These are located; on top of the valve cover and next to the vacuum reservoir. You can follow the vacuum lines from the combi valve; to the N112 valve (to the left of the N249; if you are standing in front of the car).

Here is a video; showing, a testing process for the combi valve; using a vacuum pump/tester: (Jetta 1.8T shown)

https://www.youtube.com/watch?v=08flKdnIBQk

Here is another video; going over the secondary air injection system, how it works and the most common problems:

https://www.youtube.com/watch?v=Zj-_bAiPq9Y
 

·
'02 Snap Orange 1.8T/5spd
Joined
·
152 Posts
Discussion Starter · #5 · (Edited)
Thanks for the RossTech links. In that list, everything checks out for both codes, except I haven't checked the Diverter Valve, or know where it is, and I haven't checked if the combi valve actually works. So I'll do a combi valve check next.....of course it's raining again now.

Regarding the connection/relationship of N249, it doesn't connect to the combi valve. N112 (located over by the oil fill cap) does. Am I missing something?
 

·
Registered
Joined
·
15,839 Posts
Right:

n249 for divertor valve
n112 for combi valve

The combi valve is connected to the head and a hose goes to the N112. It is near the coolant flange; that the coolant temp sensor is connected to.

Location: #6 on diagram here:

6 - Secondary Air Injection (AIR) Solenoid Valve -N112-
- Secondary air system

Volkswagen Workshop Manuals > New Beetle Turbo S L4-1.8L Turbo (AWP) (2002) > Powertrain Management > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Electronic Throttle Control Module > Component Inf

combi valve testing:

Volkswagen Workshop Manuals > New Beetle Turbo S L4-1.8L Turbo (AWP) (2002) > Powertrain Management > Emission Control Systems > Air Injection > Air Injection Control Valve > Component Information > Testing and Inspection
 

·
Registered
Joined
·
3,690 Posts
Most Secondary Airflow issues on the 1.8t are due to a broken/cracked corrugated pipe where it connects to the Kombi valve on the drivers side rear of the engine. The hard plastic pipe is usually cracked on the underside and hard to see.
 

·
'02 Snap Orange 1.8T/5spd
Joined
·
152 Posts
Discussion Starter · #8 ·
Most Secondary Airflow issues on the 1.8t are due to a broken/cracked corrugated pipe where it connects to the Kombi valve on the drivers side rear of the engine. The hard plastic pipe is usually cracked on the underside and hard to see.
I have good plastic pipes. Checked 'em both on and off the car.
 

·
'02 Snap Orange 1.8T/5spd
Joined
·
152 Posts
Discussion Starter · #10 ·
Secondary Air System is pretty straight forward.

Either the pump does not run, there is an air leak, the Kombi valve is stuck or the Pre-cat O2 sensor is lazy.
So is that how the ECU measures SAi performance, by watching voltage at the B1S1 O2 sensor?

i'm betting on stuck combi valve, at this point.
 

·
Registered
Joined
·
3,690 Posts
So is that how the ECU measures SAi performance, by watching voltage at the B1S1 O2 sensor?
Yes, on the majority of the vehicles this is the what the SAI system is monitored. One vehicles with Wideband (5-6 wire) O2 sensors the airflow needs to be monitored in a different way. Some systems (not sure if VW has this) actually have an input MAF on the SAI pump fresh air input to monitor the airflow.

i'm betting on stuck combi valve, at this point.
Could be a Kombi valve, but have also seen the impeller in the pump spin on the shaft and not move air as well.

When the car is off you should be able to blow the Kombi valve open with your mouth on a hose connected to the valve. Be careful as the output hose from the pump WILL break or is already broken, you claim it is not cracked or broken but if it is original it WILL BE cracked near the Kombi valve on the underside.
 

·
'02 Snap Orange 1.8T/5spd
Joined
·
152 Posts
Discussion Starter · #12 ·
The plastic pipe from the air pump the combi valve is 100% perfect, and like brand new. The air pump blows a tremendous amount of air....I've tested it. Could not blow the combi valve open by blowing on the hose with my mouth.
 

·
Registered
Joined
·
3,690 Posts
I checked and it appears the Kombi valve is vacuum controlled. So without vacuum applied to the Kombi valve it may be next to impossible to blow through the valve by mouth. There should be a small vacuum fitting on the side of the valve that has a small vacuum hose that is then connected to a control solenoid somewhere.

https://www.ecstuning.com/Volkswagen-New_Beetle--1.8T/Engine/Emissions/Air_Pump/ES269590/

Make sure all of the small vacuum hoses are in good shape. I do not recall the entire vacuum routing, but there are 2-3 small vacuum check valves, OE ones are black and white, they end of falling apart due to the under hood temperatures.
 

·
Registered
Joined
·
61 Posts
If you pull off the air hose at the combi valve - the one that comes for the SAI pump - then when the combi valve opens you'll get a blast of exhaust back through the valve into the engine bay. Very noticeable. If the combi valve stays shut at you won't.
 

·
'02 Snap Orange 1.8T/5spd
Joined
·
152 Posts
Discussion Starter · #15 · (Edited)
Thanks guys. I'll check these 2 systems out in more detail as I get time this week.

Did more digging through Bentley in order to locate the components and the vacuum line routings, etc. and it appears I have 3 separate problems:

1) SAI system fuction, which will probably wind up being a stuck combi valve, which gets vacuum from N112 on the right side of the valve cover.

2) A turbo system pressure issue, which right now looks like it's caused by the round black plastic diverter vavlve...which gets vacuum for actuation from N249 in the middle of the valve cover (N249 has nothing to do with combi valve function or the SAI system).

3) A CAT that's dying, because the 2 oxygen sensor do check out in readiness codes.

Found this diagram which shows the routings and relationships pretty goods, even though it's not for a Beetle:
 

·
Registered
Joined
·
3,690 Posts
Thanks guys. I'll check these 2 systems out in more detail as I get time this week.

Did more digging through Bentley in order to locate the components and the vacuum line routings, etc. and it appears I have 3 separate problems:


3) A CAT that's dying, because the 2 oxygen sensor do check out in readiness codes.
If the O2 sensor Readiness Monitors are not Clear/Ready/Pass this does not mean the catalytic converter is bad.

Make sure the engine is at the proper operating temperature, 205F, and make sure the O2 sensors are not lazy. You may just need to drive the car much further on the highway.

Also read this thread -

http://newbeetle.org/forums/1-8-lit...essure-drop-between-turbo-throttle-valve.html
 

·
'02 Snap Orange 1.8T/5spd
Joined
·
152 Posts
Discussion Starter · #17 ·
As I mentioned, both 02 Sensors do check out, either during the manual setting of readiness codes using VCDS, in the driveway...which requires the car to be run long enough at 2,200rpm, that the engine is up to operating temp, and the CAT is getting above 500*F.....or out on the freeway during a longer drive.

I'm not sure if VCDS can pick up that the sensors are lazy though.

Thanks for the link. I'll give it a read.
 

·
Registered
Joined
·
15,839 Posts

·
Registered
Joined
·
3,690 Posts
With an ODBII App like OBDFusion you can actually Log the O2 sensor behavior on cold start and determine if the sensor(s) are lazy. The post-cat sensors tend to be easier to flag as I believe most of the pre-cat O2 sensors are "Wideband" 5-6 wire O2 sensors which are a bit more difficult to properly Log.

See attached graph from a non VW vehicle with standard, non wideband pre-cat O2 sensors and you can clearly see that the Bank #1 pre-cat O2 sensor is lazy.
 

Attachments

·
'02 Snap Orange 1.8T/5spd
Joined
·
152 Posts
Discussion Starter · #20 ·
Update: Fixed

And the winner is......(I'm an idiot)......"broken vacuum hose between SAI Solenoid N112 and the Combi Valve."

Had I spent another 30 seconds on the diagnostics and tried to simply blow through the vacuum hose, or suck through it, I would have heard the huge tear down at the fitting on the Combi Valve, not to mention, seen that the hose didn't hold vacuum or pressure. *facepalm*

Cause: Just like with 100% of the rest of the car, "someone's been in here" and not put the car back together properly. Blows my mind that there are mechanics out there who work like this, but I digress. There is a metal bracket at the Combi Valve end of the cylinder head. This bracket holds a curved metal pipe, allowing the pipe to snake alongside the cylinder head, miss the Combi Valve, and then drop downward where a rubber hose attaches. The bracket has 2 bolts, one at each corner of the head. The rear bolt was missing, the bracket was shoved upwards, and the pipe was pinching the bottom of the vacuum hose, right where it meets the fitting on the Combi Valve.

With the bad end of the hose trimmed off, the bracket bolted down correctly, and the metal pipe "persuaded" slightly lower, the vacuum hose fits, holds pressure or vacuum, and when vacuum is release, the Combi Valve makes a nice internal clunk.

Thanks for all the help guys, I really appreciate it. Please help yourselves to some nice juicy, "I told you so's.":rolleyes:
 
1 - 20 of 34 Posts
Top