Posted by Alan on June 14, 2008, 10:16 pm, in reply to "Re: update"
Hi Dave,
Thanks for the reply.
Since I posted I found a 98 A6 with the same EMS that also had 5v koeo. Also Mark Murphy (thanks Mark) had an older A6 that had a constant voltage too. So it seems that the voltage is correct. Next question is why this voltage exists? I suspect it is there to allow the ECU check the injector circuit, unless someone knows better.
Now back to this problem child. Mine has 5v on inj 1,2 and 4. Nothing on 3. Bearing in mind that number 3 is the one that is not firing I feel this must be relevant. In case I had a short pulling the 5v to ground I cut the wiring at the ECU. 1,2 and 4 still have 5v coming from the ECU but nothing on 3. If I am correct about the 5v being for diagnostic purposes then that may explain why the ECU never pulses number 3. It would not however explain why 3 different ECU’s do not output the 5v on number 3. Is it possible that this 5v is also used to check circuits through other components too? I thought of this so unplugged every sensor and actuator on the engine. No change. Maybe the 5v output for inj number 3 is common to something else but is shorted within the loom?