New Stereo, Now OBD won’t work

If this is a re-post forgive me. I did search for any similar posts. And if this post is a re-post of my first attempt forgive me again. There were problems with the original post.

I bought a 98 Jetta for my son and had the factory HU replaced (Sony) since the factory unit was only a cassette which didn't work. Since the install the OBD won't work (discovered the day after the install). VW says there are can-bus wires that have to be connected in order to complete the circuit. I went back to the audio shop and had them show me their work. They didn't cut any wires and used a harness for the connections. I removed the center console and AC/Vent controls and looked for any disconnects. None were found. There are five wires on the back of the OBD plug. All were solidly connected. The only thing I did see was an ORANGE / white wire on the aftermarket harness coming from the end plugged in to the factory harness that was not connected. The wire that this wire plugs in to is either gray/blue or Lt. gray/Lt. blue. From what I've been able to find out this is a switched 12V+ lead. Obviously this wire was connected to the original HU. Could this be the source of my problem? Does this wire need to be connected? If so, to what? If not, any ideas on why the OBD doesn't function since the install? I'm sure I'm not the first person to change out the factory HU on a 98 Jetta.

As addtional information, the factory HU was made by Clarion (I think) with and 8 speaker set-up. Two tweeters in the dash and rear deck and two drivers in the doors and rear deck.

If any of you have any ideas or suggestions, I thank you in advance.

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G Tres

Welcome to the world of VW.  The OBD system is still functioning, however for the VW scan tool to function you need to have the factory deck operational. For so mysterious reason the scan tool will fry if the factory deck in not installed.  Simple solution is when the veihical goes in for service remove the aftermarket deck and plug in the factory, after service simply plug the aftermarket deck back in.  Be glad the shop was good enough to use a plug.

Wow, I was just reading through this, and sorry i dont have any helpul advice. but wow those vw engeneers must be very advanced in there thinkings... I know more about older style cars, and have a 99 chevy now, but since when did the obd system even have anything to do with a radio...   Arent the only things a radio needs 12+, GND, and remote+, and obviously the wires leaving them to the speakers... not to mention antenna.. I dont know. Why i dont drive Vws.

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99 Blazer LT.   Yellow Top. Big 3. Infinity Kappa Speakers All Around. Jensen CD/DVD flip out. 2 Infinity Kappa Perfect 12DVQs powered by a Alpine PDX600.1 (in one custom box, building a FG box)

No.... the tool will not fry if there is no factory deck. It will fry if some installer failed to actually read the instructions with the VW harness and connected the power antenna lead. It is actually the "K" line, which is a diagnostic wire. Unhook the power antenna lead.... you do not need it on 96 and newer. Use the 40-VW53 antenna adaptor if you want AM radio (has proper connection for the power antenna lead to power up the active antenna base.) And yes... you can scan the car without the factory deck. My 2004, my 2001, and my 2000 had the factory deck for all of a day when I first got them. I have no problem ever scanning either of these cars.

Gus

PS: Why is there so much misinformation and speculation about VW stuff I have no idea.... they are no wierder than most of the crap North American automakers are putting on the road. In fact, they are a lot better built, and tend to hold their value far more often.

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Wherever I go, that is where I end up......

gus 1 - Thanks for your input.

What color is this wire? Looking at the color code (not the actual wires), I see a BROWN / white stripe wire for alarm sytem control module, but nothing for a power antenna wire, which this car doesn't have (the power antenna). And if I diconnect this wire, does it reconnect somewhere else, or just insulate it and leave it loose?

Also, if I don't have this wire, what would happen if I took the car in without a radio of any kind connected? Surely VW has run in to a situation before where the radio was out for repair, or stolen. Seems like they would have some recourse such as a jumper plug or something that would allow them to run the diagnostics. 

I await your thoughts and thanks again.

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G Tres

If your car has an antenna on the roof, it's powered.

If you look on the adaptor harness, you will see there is a blue or a blue/white on the same pin as the "Alm" BROWN / white wire on the factory harness. Don't connect it to anything. Same goes with anything labelled as "K-Lin" on the factory harness.

If there is a grey/blue on the factory plug, it is probably a dimming dash light wire, or illumination.

As far as scanning the car with a non factory radio in it?   Not a problem... the only thing is when you call up the radio on the scan tool (you can... output tests, recoding, etc. can be done on it), it will have a code stating either "no communication" or "K-Line error" for just the radio (To get technical... it would show up under "Radio" in the main modules screen of the scanner.    I have one... pretty neat tool if you happen to own a VW and never go to the stealership for anything other than the odd part) The only reason the dealership is leery of non factory radios is this K'line issue and having 12V applied to it by improper radio replacement. The VAS1550 or 1551 scan tool does not have K-Line protection on it (like the Vag-Com does), and can be damaged by voltage on the K-Line.

Basically.... the moral of this story is.... don't connect to anything other than 12V, switched 12V, and ground at the harness and you will be quite fine. If you actually listen to AM radio, consider purchasing an active antenna adaptor such as the Metra 40-VW53 to properly power up the active portion of the antenna base.

Gus
Uber Vw geek.......

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Wherever I go, that is where I end up......

gus  1

The antenna is fender mounted. As I recall in discussion with the installer when he was showing me his work, he did mention that the antenna adapter he used had a small amplifier built-in. The adapter they used has a siver tube aproximately 1/2" in diameter and 4" long. I'm almost positive he mentioned that they did use the power antenna lead to accomodate this adapter. I'll confirm this later today or tomorrow by pulling the HU and looking for the wires on the factory harness you mention. If this solves the problem, as it sounds like it will, I'll let you know.

Thanks again for your input and expertise.

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G Tres

gus 1,

The antenna is fender mounted. As I recall when I went back to the shop to have them show me their work, I'm sure the guy mentioned they did use the power antenna lead to accomodate the antenna adapter they used which had a small amplifier built-in, which was approximately 1/2" in diameter and 4" long. From what it sounds like, this is likely the problem. I'll pull the HU over the next couple of days and check for the wires you mention. I'll keep you posted with the results.

Thanks again for your input and expertise.

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G Tres

gus 1,

The double post was unintentional. There was a problem with the first one. Disregard one or the other.

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G Tres

Fender mounted antenna isn't active. Only the ones on the roof. Just a plain ol' normal 40-VW10 adaptor (non active) is necessary then.

The BROWN / white is not necessary for anything.... same goes with the grey/blue (half the time the dimming circuit on most decks doesen't work that well anyways.

Gus


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Wherever I go, that is where I end up......

gus 1,

Your diagnosis was absolutely correct.

I pulled the HU on Wednesday and found the BROWN / white wire on the factory harness plugged in to the blue/white wire on the aftermarket harness just as you said. I did some minor re-wiring and re-installed the HU. It took until today to get by a shop to see if the OBD scan would work. It did and the CEL was reset. Now all I have to do is find out why the CEL comes on repeatedly for the same thing-emission loss/leak (slow leak). It'll be somewhat easier now that the OBD is working again.

Your input was invaluable. Please accept my sincere thanks for your willingness to share your knowledge and expertise. I am in your debt.

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G Tres

What motor? I may be able to shed some light on this as well......

Gus


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Wherever I go, that is where I end up......

The motor is the 2.0 liter, 5-speed trans. The throttle body was changed by the dealer just before we purchased since the car wouldn't idle with the A/C running. The auto shop that did the TBI said he thought the problem was related to the gas cap not put tightly enough after re-fueling. Taking that info, I noticed the gas cap was not the original and bought the correct one from VW. At the same time I replaced the plastic end on the dip stick tube was also broken. I had the CEL reset with both of these items changed and the light stayed off for 6 days, came on for 1 day, went off again for 2 days and came back on. Since the OBD works again, as previously stated, I had the CEL reset Saturday. My son called on his way to school today and said it was back on. VW seems to think it's something like a hose with a crack or pinhole causing the problem, which they weren't able to scan the car as you already know from my original post. I'm sure they can now since the OBD funtions again, but if you have any suggestions, I would appreciate your input.

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G Tres

Yeah, it does sound like a vaccuum problem.

Check all of the vaccuum hoses very carefully.... an old trick is to carefully mist some WD40 or Brakleen along any suspect hose. When the motor revs up from sucking in the solvent, you found your leak. The other thing to try is use a normal hand suction pump to pull a vaccuum on the system, and carefully listen for any leaks.

The other thing to check is if the TPS (throttle position sensor) was properly aligned and learnt to the computer when it was swapped over.   Did the dealer give you any indication as to the codes they pulled from the car when they scanned it? Even a code number would help.

Gus


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Wherever I go, that is where I end up......

The only code number I know of was from the guy I know at a shop nearby. Seems like it was 402 (I can double check this since the CEL is on again), which he looked up and got the "emission leak/loss (slow leak)" diagnosis. This was the same diagnosis given by the shop the car dealer uses. When I was at VW they said they can pinpoint the exact location. How, I don't know unless their approach is wholesale parts changes to "pinpoint" the problem area.

I can certainly take the car back to the shop the dealer uses, or call the guy at the shop that did the work and ask him about the TPS alignment and computer read at installation. There may be something there. If this can be solved without VW that would save me their $76 diagnostic charge which is not applicable to the cost of the repair. While I'm not opposed to spending money to have this problem found and repaired, I was rather surprised at this particular VW dealerships policy of two separate charges for the same problem. That's not typical for other car dealerships in this area.

I'll keep you posted and thanks again.

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G Tres