Hello, So recently while driving my 2001 Audi TT Quattro I was at a light when my car suddenly shut off, I tried to start it back up (thinking my knee had bumped my key shutting the car off) but it wouldn't start back up (the engine will still turn over). After letting my car sit for about an hour it turned on and I drove home. It hasn't shut off at a light again (yet). It has now started to not restart after driving for about 10 miles, then after about an hour of the car sitting there it will not restart until the engine has cooled down (again the engine turns over fine).
I can hear the fuel pump turning on and priming the car.
Today when it did it I disconnected both fuel lines to see if it was some vapor lock happening, I dont think thats it either (fuel came out of the lines and all pressure was out of the lines and I reconnected them let the fuel pump prime the engine). Is there some sensor or relay that would cause this?

 

So just put the car on my uncles VAG-COM and I got these 3 codes:
18010 - Power Supply Terminal 30
P1602 - 35-10 - Voltage Too Low - Intermittent
17925 - Power Supply Relay For ECU (j271 or j363)
P1517 - 35-10 Electrical Malfunction - Intermittent
16706 - Engine Speed Sensor (g28)
P0322 - 35-10 - No Signal - Intermittent

After some searching the 18010 code should just be the battery not connected properly (while working on the rad fans I was unplugging the battery a lot so I think it could have come from there (but I also don't know if the car had ever had a VAG-COM put on it)). The bottom code (16706) I have no clue where it came from or entirely what it means. The the code that I think is most likely to cause it is the middle one (17925). Does anyone know where to start on this code?

 

First thing I'd look for is loose ground connections in the engine bay wiring harness. Find them and loosen them up and retighten them. Also check the ground straps that connect the engine to the body of the car. Loose grounds can cause all kinds of weird electrical issues and are generally the FIRST thing to look for when diagnosing electrical issues.

 

ok once I get home I'll run through all my grounds. what are the odds that the relay has gone bad?

 

So I havent gotten a chance to look at it, due to me getting off work and having to run to my second job to finish some stuff. Basically my car is now dead across town...... But it seems to only do it when its hot outside. What could this be? Im still going to check all the ground wires and test that relay. But what would make it do it only when its hot?

 

Because when things are hot, things are more likely to loosen up.

 

i like the engines speed sensor code because that is the direction im leaning with mine having the same problem. Engine coolant temp sensor or something of that nature. The computer getting the wrong signal when the motor is hot and injecting a mix the motor cant burn.