[s-cars] Fuel Pump Relay (J17) Function - More than I thought. (Part 2)

[Dave Forgie]

Part 2 (Audifans is giving me grief):

"From the diagram, it can be seen that the ECU to signal to the FP
relay comes from Pin 3/55 of the ECU as a brown wire with a yellow
stripe, i.e. a switched ground. This pulls power from the No. 15
switched power terminal under the drivers side knee bolster. With
current allowed to run from 15 to ground (via the ECU), the relay's
electromagnets engage two contacts which then pull power off the 30
terminal (I don't think that one is switched. This allows current to
flow from the 30 power line to the J17 relay outputs 87A and 87F. 87A
energizes the N75 wastegate frequency valve and the five injectors
(which get their duty cycle control from the ECU). 87F energizes the
fuel pump (via a green wire to Fuse No. 17 and then a green wire with
yellow stripe to the FP) and the O2 sensor via a black wire to a 12 Amp
circuit breaker located under the passenger side (right side) kick
panel.

As a result, some running and/or stalling problems could be related to
a bad signal between the ECU and the J17 FP relay or the J17 itself.

HTH somebody."

Diagram at:

http://forums.audiworld.com/s4s6/msgs/133907.phtml

Dave F.