'02 ALH with CEL, VCDS ODB2 not connecting. HELP!

Mopar-VW-Dieselman

Well-known member
Joined
Apr 14, 2008
Location
Inland Empire, SoCal
TDI
1992 HD 3/4 Ton Dodge Cummins, 2002 Blue VW Jetta TDI Automatic
I have an '02 Jetta ALH with a CEL.
It started after I received a low coolant light. I added VW coolant & distilled water (50/50) to reservoir and low coolant light went out. About 3 miles down the road I received a CEL.

I "tried" to connect VCSD to OBD2, but received a connection error. I tried several times, same issue. I used same cable and laptop on '97 Passat TDI and had no problem connecting and running a diagnostic, so I know the VCSD cable and laptop USB connections are good.

Any thoughts other than a VW dealer to resolve the issue. Maybe something I can check?

I took a look under the dash and did not see any obvious wire or other connection problems.

I have a job interview coming up Monday or Tuesday and need it fixed. I'd hate to have it quit on me on the way to an interview (not a good thing). This is the first time I've ever had an issue with the VCDS and OBD2 not connecting.

Any recommendations would be greatly appreciated.
 

UhOh

Top Post Dawg
Joined
Dec 24, 2014
Location
PNW
TDI
2000 & 2003 Golf GLS
Have you ever been able to get this combo working on this car? If so, when was the last time (and what has changed since)?

Might be worth a shot to disconnect the battery cables and touch them together (to discharge your electrical system).
 

BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
Check relay 109, re-seat it, If it's black get a new one.
Check fuses.
Any add on wiring?
Does the little light on the VCDS light (if applicable)?
Do you have the latest software (it should still connect)?

Back in the early days there were a lot of discussions on Coolant Migration. The coolant level sensor could crack and fluid would wick into the wire looms, real bad news. Hope it's not that.
 

Mopar-VW-Dieselman

Well-known member
Joined
Apr 14, 2008
Location
Inland Empire, SoCal
TDI
1992 HD 3/4 Ton Dodge Cummins, 2002 Blue VW Jetta TDI Automatic
Have you ever been able to get this combo working on this car? If so, when was the last time (and what has changed since)?

Might be worth a shot to disconnect the battery cables and touch them together (to discharge your electrical system).
Yes, I've connected several times over the past several years. Only change was the "low coolant" light and adding coolant/distilled water (50/50 mix)

Check relay 109, re-seat it, If it's black get a new one.
Check fuses.
Any add on wiring?
Does the little light on the VCDS light (if applicable)?
Do you have the latest software (it should still connect)?

Back in the early days there were a lot of discussions on Coolant Migration. The coolant level sensor could crack and fluid would wick into the wire looms, real bad news. Hope it's not that.
I will check the fuses. Nothing added to car for over 140,000 miles and have made connection with this laptop and VCDS cable multiple times. I do have the latest VCDS software installed too. No the light on the VCDS does not come on. Car starts and runs just fine, so I don't think it's the 109 relay, but I'll take a look at it and re-seat it.
 
Last edited:

UhOh

Top Post Dawg
Joined
Dec 24, 2014
Location
PNW
TDI
2000 & 2003 Golf GLS
Peek inside your wiring loom coming from the coolant reservoir tank and make sure it's not wet there. I think that I, and Bob:D, would feel better knowing that there's NOT that nasty coolant migration issue happening!
 

Mopar-VW-Dieselman

Well-known member
Joined
Apr 14, 2008
Location
Inland Empire, SoCal
TDI
1992 HD 3/4 Ton Dodge Cummins, 2002 Blue VW Jetta TDI Automatic
Peek inside your wiring loom coming from the coolant reservoir tank and make sure it's not wet there. I think that I, and Bob:D, would feel better knowing that there's NOT that nasty coolant migration issue happening!
Good idea, I'll check that as well. I did find a burned out 7.5 amp fuse. The "small size". I have a bunch of the standard size replacements, just not the small ones. My wife went to get a box of various amp small fuses. I hope that's the culprit. I'ts from space #12 if that helps any of you out there.

When my wife gets back, I'll be off line to test VCSD. This laptop is in a docking station and the WiFi doesn't work in the garage.
 

JB05

Top Post Dawg
Joined
Oct 20, 2005
Location
Il.USA
TDI
Golf,2005,anthracite blue
My old lap top would not connect on its battery power alone. I had to plug into an outside source of electricity.
 

Mopar-VW-Dieselman

Well-known member
Joined
Apr 14, 2008
Location
Inland Empire, SoCal
TDI
1992 HD 3/4 Ton Dodge Cummins, 2002 Blue VW Jetta TDI Automatic
Thanks a million UhOh and BobnOH.
I replaced the 7.5 amp fuse and the VCDS connected just fine.
Error: 16490 - Manifold / Barometric Pressure Sensor (G71) / (F96)
P0106 - 35-00 - Implausible Signal
I cleared the code and drove it around the block and it didn't come back on. I'll look more into it later, I have a business call in less than 1/2 hour.

I checked the wire loom and connector. BONE DRY. BUT I did add some DIELECTRIC to the connection to help prevent any other issues in the future.

When I get back to it in a few hours and drive it a bit more, I'll update you all.

Thanks again UhOh and BobnOH.
 

Mopar-VW-Dieselman

Well-known member
Joined
Apr 14, 2008
Location
Inland Empire, SoCal
TDI
1992 HD 3/4 Ton Dodge Cummins, 2002 Blue VW Jetta TDI Automatic
....just a little update....
I put about 100 miles on the car yesterday, still no problems.

I connected the VCDS just fine this morning and ran a diag. on it, just in case there was still a problem lurking without a CEL.
Everything just fine!
 
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