Sometimes a bad cluster can cause that. Do you have a spare? If not, you can check for 12v (I think it's 12v, not ground) from the ECU with the bulb removed, to verify it's the ECU sending a signal, not a screwup in the cluster.

The light should come on at startup, turn of from the bulb check, and then re-light if there's a fault, I think, but don't quote me.

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The light comes on at start up, turns off. Then comes back on and stays on. So it's working properly. Haven't checked 12v from ecu yet. If it is working properly, what would cause me not to be able to read the code out of the obd port? I tried my scanner and an O'Riellys scanner

 

Thanks for the response!

I'll try another cluster soon. His speedo only works some times. Which leads me to believe it's the cluster. But the should be codes because it will sputter on occasion.
What are the chances it's the ecu?

 

Lower than it being a cluster.

 

Bump! Any thoughts? Pretty confused

 

Did you try what I said?

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If the car has an aftermarket radio it may be messing with the code reader. There's a wire in the harness that needs to be cut or jumped search Ross Techs website for more info.
The coolant bulbs often fail, putting a used one in is still taking a chance that the sensor inside won't work. Did you clean it out before installing ? If you don't want to spend the $20 for a new one make sure it's cleaned out as good as can be, some people have had good luck with CLR. Also what type of coolant is in the car, if someone put generic green coolant in without a complete flush it can mix with the VW coolant and turn into sludge destroying the sensor.

If the car runs at all then the ECU is fine.
Have you tested the MAF?
Make sure the ground wires are clean and making good contact.
Replace any vacuum hoses that look or feel like they're deteriorated.
Have you checked the timing and timing belt?

 

Thanks for the reply!

So the car doesn't have a radio but I'll the radio wires are properly separated with connectors. So they shouldn't be connecting.

As far as the coolant goes. When he first got it, it had green coolant so we flushed it out and put in g12 but is noticed today it could use another flush.

Maf was cleaned but not replaced or checked

 

The only thing I could think of is a grounded signal line like mentioned above, but I don't even think a 96 has that wire going to the radio.

There is a connector strip above the fuse box, that could have something unplugged. Can you deep down the fuse box and get a look at the back of that strip?

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There are fuses mounted above the fuse box you need to check, does the cigarette lighter socket have power?
I think they're on the same circuit

 

Alright I'll check all of those tonight. I no the cigarette light has power cause I check those those fuses

 

Any one have a pic of the plugs going into the junction box for the obd? I found mine and I'll that's plugged into it is a yellow plug with a grey/white and yellow wire. Which is what bently says. But I should have 4 other wires coming out of it I think

 

There should be one from the ecu, one from the abs, one from the airbags, and one from the auto trans (as well as from a diode connected to 12v switched) if you had one.

If you only have the one connector, that's probably the one to the dlc? You'll need to search for the missing wires behind the fuse box.

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Just found one on a different mk3. All three of those were pulled out. Code reader works now! Problem solved! A hole laundry list of codes popped up so time to start narrowing it down!

Thanks for the help!