No speedo and having problems

[karter74]

Anybody running a KAAZ dif (or any without a speedo drive gear) and had any problems with a vehicle speed sensor code. What did you do? Any Ideas? O2A and 98 VR6.

[pfcs]

I've had people bring me OBD II ABA A3s that they had swapped to a 5 spd mt and now wouldn't pass inspection because they posted a code for VSS fault but they ran fine as far as I know. This isn't showroom stock, what's the problem?
(we were able to patch in a VSS signal & pass NJ inspection)
(www.philscars.com)

[karter74]

I've had people bring me OBD II ABA A3s that they had swapped to a 5 spd mt and now wouldn't pass inspection because they posted a code for VSS fault but they ran fine as far as I know. This isn't showroom stock, what's the problem?
(we were able to patch in a VSS signal & pass NJ inspection)
(www.philscars.com (http://www.philscars.com))

Thanks for the Info. How did you patch in a VSS signal. The car cuts out at 5800 if it does not have that signal. Has been intermittent but seems to always bee there during a race. Finally figured out it is because it checks readiness on the warm-up lap and sets the code. If I run hard from the time I hit the track no problem. Took us a while to figure out what it was. Not fun loosing a good part of my power band...:shrug:

[pfcs]

A quick look @ 96-99 A3 Bently, 97-266 to 272 wiring diagrams, (7 plates):
VSS enters ECM (J220) @T68/65 <from <W/1-(fusebox bridge)-U2/2< from <T28/20 -(instrument cluster)-T28/27 <VSS (G22) vss signal to clstr, from.5mm white wire, center pin of VSS.
You could send VSS signal directly to J220 T68/65 (eng cntl mdl 68 pin connector, pin 65)
This was off ABA/4cyl digram but I think AAA is similar or identical in this area.
www.philscars.com (http://www.philscars.com)

[Dave Zaslow]

Karter74,

As you have discovered, the ecu must see a clean vss signal or when it hits that rpm or it goes into a limp mode and maximizes the injector on time flooding the engine with gas. Lots of A3's have this problem and the answer is to run directly from the VSS to pin 65 at the ecu as Phil has noted.

Do you not have a VSS on the tailshaft of the trans?

DZ

[karter74]

Thanks for the replies. Seems I either need to get a drive gear on the dif or make a signal for the computer... At least I know how to fix it. Just need to find the best way.

[shwah]

I don't think the VSS comes from the speedo drive. But I have not ever owned an A3...

[Dave Zaslow]

Chris,

The VSS signal runs in-out of the cluster and creates the signal for the speedo. There is no speedo drive.

If you follow the wiring diagram and trace the insane route this signal takes it is no wonder that the ecu gets a crap or no signal and goes into limp mode.

I replaced every bit of my engine harness and relay/fuse box. I advise others to jump from the VSS to pin 65 first.

DZ

[karter74]

Seems according to kaaz there is room for the speedo drive gear. I just need to tear the trans down over the next week and get it fixed. That's all:happy204:

[Bill Miller]

Seems according to kaaz there is room for the speedo drive gear. I just need to tear the trans down over the next week and get it fixed. That's all:happy204:
Sure seems like jumping the VSS is a LOT easier than tearing the trans down!

[karter74]

I do agree and am rethinking things. Just need to find a good signal. Wheel speed sensor won't work. I don't want to tap into the cam or crank signal and cause loss. I am open to ideas.

[pfcs]

If you can install the speedo gear on the diff carrier w/Kaz, then it would be the most sensible path and not too difficult/doesn't require too much dis-assembly.
Other "creative" remedies may be of questionable legality and effectiveness.

[Knestis]

On our 2.0 MkIII, the KAAZ we used was completely compatible with the VSS. It was never a question.

We had multiple wire faults per what's been described above.

K

[Dave Zaslow]

I do agree and am rethinking things. Just need to find a good signal. Wheel speed sensor won't work. I don't want to tap into the cam or crank signal and cause loss. I am open to ideas.

The VSS gives wheel speed as a 0 to 4vdc pulse so the ecu knows how fast you are going. I think it's once per wheel/axle revolution. The test is in the bentley manual. If you have a wheels speed sensor as part of the abs that will not do as there are too many pulses so the frequency will be way off.

DZ

[karter74]

I did want to say thanks to everybody. It is nice to get some decent help from a forum. Often is not the case.

The transmission builder is going to do the work for free if I get him the trans. I like the idea of have it fixed the right way and it gives me a speedo. As Phil pointed out in a message that can help in other ways.

[Flyinglizard]

For some reason I thought that the ring gear and the diff gear might be going about the same speed. Than it is about making the right amount of pulses.

[karter74]

started a new thread but this seems to have the attention of people who would know. Gear ratios for non IT gearbox?? suggestions?