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2004 Passat B5.5 Wagon GL
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Discussion Starter #1
Hi all, I am new, so please bear with me here...

I have a new to me 2004 B5.5 Passat Wagon GL that the previous owner let water ingress upon (filled rain tray and well into passenger compartment)... They replaced the ECU before I purchased, and the car runs and drives, but has a few Gremlins to say the least...

Symptoms:

-down on power
-once up to temperature, the revs will drop and EPC light comes on (often accompanied by CEL)
-will stall when coming to a stop, or starting occasionally
-one time it failed to hot-start after driving...only to start once the car had cooled
-temperature reporting seems a little off--it seems slow to get up to temp, and fluctuates some while driving down the freeway
-CCU was wet and corroded...clean contacts some (they are far from perfect) and cleaned ground. Once I did this the door locks and windows began to function again.
-CEL light is on, and codes are consistent in VCDS

Tried:
-Cleaning ground under cowl, in rain tray and behind coolant res.
-Cleaned and replaced relays and fuses in ECU box

Next Ideas:

-Replace Engine Speed Senor (stalling, hard start, down on power)
-Replace Coolant Temp Sensor (address temp. reporting, maybe hot start issue?)
-Replace MAP Sensor
-Investigate grounds and see if any are corroded and can be cleaned up further

VCDS Lite 1.2 (registered) Auto Scan Result:

VCDS-Lite Version: Release 1.2
Tuesday, 15 September 2020, 11:52:18:36669


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

-------------------------------------------------------------------------------
Address 01: Engine Labels: Redir Fail!
Controller: 4B0 906 018 DP
Component: 1.8L R4/5VT G 0002
Coding: 0016501
Shop #: WSC 05311
VCID: 7297D6F62DB7
4 Faults Found:
16706 - Engine Speed Sensor (G28): No Signal
P0322 - 004 - No Signal/Communication - Intermittent
16490 - Manifold / Barometric Pressure Sensor (G71) / (F96): Implausible Signal
P0106 - 008 - Implausible Signal
17841 - Secondary Air Pump Relay (J299): Open Circuit
P1433 - 004 - No Signal/Communication
16514 - Oxygen (Lambda) Sensor B1 S1: Malfunction in Circuit
P0130 - 008 - Implausible Signal
Readiness: 0110 1101

-------------------------------------------------------------------------------
Address 03: ABS Brakes Labels: 4B0-614-517.LBL
Controller: 4B0 614 517 G
Component: ABS/ESP front 3428
Coding: 04275
Shop #: WSC 05311
VCID: 253DFDAAACF9
No fault code found.

-------------------------------------------------------------------------------
Address 15: Airbags Labels: 6Q0-909-605-VW5.LBL
Controller: 1C0 909 605 C
Component: 09 AIRBAG VW61 04 0003
Coding: 12345
Shop #: WSC 05311
VCID: 243BE0AEA7C3
No fault code found.

-------------------------------------------------------------------------------
Address 17: Instruments Labels: 3B0-920-xx5-17.LBL
Controller: 3B0 920 929 B
Component: KOMBI+WEGFAHRSP VDO V04
Coding: 15235
Shop #: WSC 00000
VCID: 263FFAA6D1FF
WVWND63B94E210227 VWZ7Z0C8521541
2 Faults Found:
01336 - Data Bus for Comfort System
80-10 - Single-Wire Operation - Intermittent
00476 - Control Module for Fuel Pump (J538)
49-00 - No Communications

-------------------------------------------------------------------------------
Address 19: CAN Gateway Labels: 6N0-909-901-19.LBL
Controller: 6N0 909 901
Component: Gateway K<->CAN 0001
Coding: 00006
Shop #: WSC 05311
VCID: F0935CFEA3BB
3 Faults Found:
01336 - Data Bus for Comfort System
80-10 - Single-Wire Operation - Intermittent
00476 - Control Module for Fuel Pump (J538)
49-00 - No Communications
00463 - Control Module for Digital Sound Package (J525)
49-00 - No Communications

-------------------------------------------------------------------------------
Address 46: Central Conv. Labels: 1C0-959-799.LBL
Controller: 1C0 959 799 C
Component: 08 Komfortgerát HLO 0003
Coding: 00258
Shop #: WSC 00028
VCID: 370127E20655
2 Faults Found:
01336 - Data Bus for Comfort System
80-00 - Single-Wire Operation
00931 - Locking Module for Central Locking; Rear Right (F223)
27-00 - Implausible Signal

-------------------------------------------------------------------------------
Address 56: Radio Labels: 3B7-035-1xx-56.LBL
Controller: 3B7 035 180 F
Component: Radio NP2 0016
Coding: 00401
Shop #: WSC 05311
VCID: 2339E3B2A2CD
No fault code found.

End --------------------------------------------------------------------------------------------------
 

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Have you cleared the codes yet? I'd be sure to clear all codes then drive around a while to see which come back. Some may be very old and irrelevant. Any real problems will reset a code.
 

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2004 Passat B5.5 Wagon GL
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Discussion Starter #3
Good question--I should have been more clear. Those are the codes after clearing via VCDS. There were more beforehand, but those are the ones that persist after going into each module and clearing manually.
 

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Looks like you are going to go harness-diving. First would be getting into the ECU box and checking out the wiring and SAIP relay. Then you'll want to open up all the tape covering the CCM wiring under the driver seat all the way to the a-pillar. There are splices in that harness that have likely corroded and/or broken.

If you want to throw some parts at it, you're on the right track and the ones mentioned aren't expensive just to replace for peace of mind.
 
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Discussion Starter #5
Looks like you are going to go harness-diving. First would be getting into the ECU box and checking out the wiring and SAIP relay. Then you'll want to open up all the tape covering the CCM wiring under the driver seat all the way to the a-pillar. There are splices in that harness that have likely corroded and/or broken.

If you want to throw some parts at it, you're on the right track and the ones mentioned aren't expensive just to replace for peace of mind.
That was what I worried about--diggin' in the harness sounds like a bit of a nightmare.. I have access to a donor car to pull many of those sensors off of, so I thought it might be a logical starting point. Could a short in the hardness lead to those implausible sensor readings? Does utilizing a used sensor (even if only for testing to see if they address/change the output in VCDS) a good/worthwhile idea in your estimation?

I did clean the connects on the relays in the ecu, but I did not test them. Honestly, this is kinda my first rodeo diving into this level of electrical nightmare.
 

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Discussion Starter #6
Thanks to @VAGguy & @Iowegian for feedback earlier!

UPDATE:
I worked on the car this weekend and am seeing progress. The engine fault codes (the module/issues am focused on first) that remain from the original scan are:

VCDS-Lite Version: Release 1.2
Monday, 21 September 2020, 13:33:31:36669
Control Module Part Number: 4B0 906 018 DP
Component and/or Version: 1.8L R4/5VT G 0002
Software Coding: 0016501
Work Shop Code: WSC 05311
VCID: 7297D6F62DB7
2 Faults Found:
16490 - Manifold / Barometric Pressure Sensor (G71) / (F96): Implausible Signal
P0106 - 008 - Implausible Signal
16514 - Oxygen (Lambda) Sensor B1 S1: Malfunction in Circuit
P0130 - 008 - Implausible Signal

Fixes:


Engine Speed Senor fault: I replaced it with a sensor from my donor/parts car. The new ESS solved the issue, and now I have cruise control back and am out of EPC (& what felt like limp) mode! Car drives much better, but feels down on power still (more on that below).

SAIP fault: fixed by the replacement of relay #373 in the ECU box, taken from donor car. The relay that was in there "looked fine" but upon removing the plastic cover, was completed rusted out and the arm did not move to close the circuit (as VCDS suggested).

Faults that remain, and where I am seeking advice:

o2 sensor -- Swapped the upstream sensor off of the donor/parts car, and there was no change. I do not know that the sensor was any good to begin with. Is there a way to check resistance (etc) on the sensor(s) to see if they are any good to begin with before shell out for a new one?

MAP sensor -- My donor car is also a AWM but has the larger diameter and different style MAP sensor, so I cannot test a replacement part for a fix. I tried to clean the original, apparently faulty MAP sensor with MAF cleaner, but it still isn't working. I presume this sensor's failure is why the car feels "down on power," and seems to stumble off the line? Same question as above--can it validate this part is not working by checking the part with a multimeter?

Disclosure: electrical is NOT my strong point, so any advice appreciated (and ideally explained like I am a 5 year old!).

Finally, my other gremlin is the car NOT wanting to crank (whatsoever, not even a click) when the car is hot, and sometimes when the car is cold. When it does crank, it starts instantly. Any ideas here??

I have read all the "no crank" threads I can find on here & I am thinking this issue may be:
  • Clutch position switch (cycling the clutch a time or two seems to get it to crank when it is cold)
  • Ignition switch (less likely)
  • Starter solenoid (would possibly explain why it is more prone to this issue when hot?)
  • or...?
Any suggestions or encouragement is appreciated! I will update this thread as I make progress in the event it is helpful to anyone else.

Thanks everyone!

-RSS
 

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SAIP fault: fixed by the replacement of relay #373 in the ECU box, taken from donor car. The relay that was in there "looked fine" but upon removing the plastic cover, was completed rusted out and the arm did not move to close the circuit (as VCDS suggested).
These relays usually fail from arcing and if your relay was truly rusted I would check and/or clean the ECM board. Electronics of any kind don't like corrosion or moisture and if the relay was rusted everything in that box should be checked.
 

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Discussion Starter #8
These relays usually fail from arcing and if your relay was truly rusted I would check and/or clean the ECM board. Electronics of any kind don't like corrosion or moisture and if the relay was rusted everything in that box should be checked.
Previous owner replaced the ECM before giving up on the car and selling to me. Looks pretty clean and corrosion free in there now. I replaced the ECM relay as well, just for good measure.
 

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Sounds good. I'd check and clean all the plugs, wires and splices you can see too then. No need to do anything that looks clean and dry but if there is any sign of crud I'd clean it with an electrical contact cleaner.

For the O2 sensors, you can measure the resistance of the heater elements but if those are bad they almost always throw a specific code so there isn't much testing that can be done with just a multi-meter.
 

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Sounds good. I'd check and clean all the plugs, wires and splices you can see too then. No need to do anything that looks clean and dry but if there is any sign of crud I'd clean it with an electrical contact cleaner.

For the O2 sensors, you can measure the resistance of the heater elements but if those are bad they almost always throw a specific code so there isn't much testing that can be done with just a multi-meter.
@Iowegian thank you--appreciate your support/guidance on this endeavor.

Got it--it will pull up the carpet again and have a look around for crusty wiring/grounds/connections. Ditto in the ECM box.

The "old" o2 sensor had a fault code at one point about the heating element...haven't seen it since this other one was put in. I guess i will plunk down on a new o2 sensor (it is a wear item anyway) and hope that solves for one of my codes!

I have been told the MAP sensor could be a leak in the intake/boost piping somewhere...do I need to pressure test, or is spraying some start fluid on hoses and connections (and listening to the engine) a sound approach?
 
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