2007 A4 2.0T Quattro No Crank

So, Ive solved this issue. This may not be the case for everyone, but it was for me.

I replaced the starter on the car but still had a no crank. With the help of a friend, a multimeter and a new battery, we started at the starter interlock relay. On this car, it is located under the hood on the driver's side of the car, by the windshield. There are 4 screws to remove to gain access to the ECM, and the SIR. The SIR is the relay furthest to the front of the car inside the relay compartment. We removed it and, with the battery connected, turned the key to crank, and checked pin 5. If there is 12VDC there, then your system is working correctly. Now, this lead us to investigate the Starter Signal Wire that plugs into the solenoid on the starter. Using a jumper, we touched the batter cable (on the solenoid) and touched the pin on the solenoid. Low and behold, the motor cranked.

So, we inspected the connector and the female pin inside that connector and found it to be corroded. We cleaned it, used a pick to tighten up the connection, and plugged it back in. When the moment of truth arrived, I cranked the car and she fired right up.

This is my experience, yours may be different. But with the lack of troubleshooting information out there for these cars, anything helps. I have attached a schematic from All Data to give you a hand.

Hope this helps.