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VCDS Lite - First scan ever, N75 Open Circuit & Brake Light Switch Implausible Signal

4044 Views 6 Replies 3 Participants Last post by  Tomvw
VCDS Lite - First scan ever, N75 Open Circuit & Brake Light Switch Implausible Signal

VCDS-Lite Version: Release 1.2
Saturday, 01 March 2014, 11:56:16.


Chassis Type: 3B - VW Passat B5
Scan: 01,02,03,08,15,16,17,19,35,36,37,46,47,55,56,57,58,75,76,77

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Address 01: Engine Labels: None
Controller: 8D0 907 557 P
Component: 1.8L R4/5VT MOTR AT D04
Coding: 06051
Shop #: WSC 05314
VCID: 3D0DBAF72469
1 Fault Found:
17956 - Boost Pressure Regulation Valve (N75): Open Circuit
P1548 - 35-10 - - - Intermittent
Readiness: 0000 0000

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Address 02: Auto Trans Labels: 01V-927-156.LBL
Controller: 8D0 927 156 BM
Component: AG5 01V 1.8l5VT USA 8508
Coding: 00000
Shop #: WSC 00000
VCID: 79856EE770C1
1 Fault Found:
00526 - Brake Light Switch-F
27-00 - Implausible Signal

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Address 03: ABS Brakes Labels: 8E0-614-111-ABS.LBL
Controller: 8E0 614 111 B
Component: ABS/EDS 5.3 FRONT D00
Coding: 0273004283
Shop #: BB 24332
VCID: 1D4D5A7784A9
No fault code found.
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Right now I'm at the diagnosis stage, figuring out a method to troubleshoot and fix these errors. Here's what I know.

My friend did a VCDS scan a year back and I had the N75 valve issue then. I ordered a new VAG replacement N75 (no upgrade, made sure I got the right revision for a B5 1.8T) and I still have the error today. So that tells me something around the N75 is bad... wires or vaccuum hoses? At this stage, I'm not sure what else could cause the fault code (i.e. a boost leak or bad wastegate?)

For the brake light switch, I have a driver side taillight bulb out, and my high-mounted 3rd brake light only has 1 LED out of the bunch working. I'm guessing between the taillight and third brakelight I would see this fault code.
The faulty lights are not the cause of this.
00526 This can be ignored. See Special Notes: 00526 - Ross-Tech Wiki

17956 Check wiring and connections (Open circuit): 17956/P1548/005448 - Ross-Tech Wiki

You should replace the tail light bulb. If the third brake light has LEDs they could have bad solder joints re-solder them or
replace LEDs if faulty (ensure correct polarity), if it has bulbs replace them.
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The faulty lights are not the cause of this.
00526 This can be ignored. See Special Notes: 00526 - Ross-Tech Wiki

17956 Check wiring and connections (Open circuit): 17956/P1548/005448 - Ross-Tech Wiki

You should replace the tail light bulb. If the third brake light has LEDs they could have bad solder joints re-solder them or
replace LEDs if faulty (ensure correct polarity), if it has bulbs replace them.
Thanks Tom, I didn't know all that info was available.

Time to look up the wiring diagram for the N75 and see if anyone's had the same problems on here.
With the licenced version of VCDS, you can cycle the N75 (and pretty much any other electrically-operated valves) using output tests. If the valve doesn't click during the test, and the N75's coil isn't open (no continuity across the two pins) - then perhaps the wiring is broken somewhere between the valve and the ECU.
With the licenced version of VCDS, you can cycle the N75 (and pretty much any other electrically-operated valves) using output tests. If the valve doesn't click during the test, and the N75's coil isn't open (no continuity across the two pins) - then perhaps the wiring is broken somewhere between the valve and the ECU.
I wish I could buy the licensed version of VCDS but I'm in the middle of an engine swap on my Jeep and all of my cash is tied up into that project until I get it running. VCDS is $249. :icon_eek:

I don't like to (mostly because I'm not that great at it) but I have some experience tracing wires and using a multi-meter. I'll start at the N75 valve and work my way back to the ECU as necessary. I did a search and found that the yellow wire at the N75 typically gets disconnected somehow:

http://www.passatworld.com/forums/42-volkswagen-passat-b5-discussion/244130-boost-gauge-says-4-psi-but-feels-stock.html
http://www.passatworld.com/forums/42-volkswagen-passat-b5-discussion/121935-17956-boost-pressure-regulation-valve-n75-fixed.html
http://www.passatworld.com/forums/newreply.php?do=newreply&p=3339194

And if it's not an electric problem, I'll probably do a boost test. I received a compressor for Christmas so I can finally try this:
:: a4mods.com :: - The Premiere Audi A4 Modification Guide and Pictures Library
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See last paragraph.

VCDS-Lite Unregistered (FREE) will read all DTCs in all your scannable modules, and perform some tests and procedures.
You will need the registered version ($99) for some procedures such as TBA etc. For more info on functions Etc.
VCDSCompatibilityCharts.pdf

You can buy an interface like this OBD2 VAG-COM USB Cable Scanner Audi VW, on eBay for about $10.00.
NOTE: I do not recommend this or any particular one, but most seem to work well.
I suggest you DO NOT use the software supplied on CD with the cable, these are old and restricted, and many have Viruses.
(This connects to the OBDII Port in the car, and to a PC or Laptop Etc. running Windows)
Then download the VCDS-Lite, FREE software (or registered software for $99). From: Ross-Tech: VCDS-Lite
They also supply interface cables with full versions of VCDS from $249.00.

You can start with VCDS-Lite unreg. If you want more functions upgrade online for $99 to registered. If you still want more functions upgrade to the full version and Ross Tech cable. Ross Tech have been crediting the $99 Lite registration toward a full version.
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