Note: This may or may not apply to non-North American UrS4s and UrS6s.
I had previously did a little documentation of the NAmerican UrS4/S6 Central Relay panel (above the Driver's side knee bolster) and knew about the relay in position 4 on that relay panel. (For the automatic cars, it is even labelled the Starter Interlock Relay, i.e. you have to be in Park or Neutral before the ignition switch will energize the starter when the key is turned to START). The question was if the manuals don't have that relay per se but they have a "back-up light" relay, why does it seem to be involved in the starting of an UrS with a manual transmission. I had also documented that some ROW (rest of the world) UrSs did not have the "back-up light" relay but had a jumper instead. Based on the recent thread, I decided to investigate further.
Relay in question is the "204", third from the right:
I first checked the Bentley and found the relay and its connections spread over at least three electrical pages. Hmm..not easy to document. Then I checked the FAQ and found a generic 1996 A6 quattro starter diagram that Nate P. (ImQuattro) had posted. I printed that off and then annotated it based on the Bentley. The result is this:
So based on that diagram, my interpretation is that *IF* the Central Locking/Alarm System control module (on the central locking pump, beside the battery, in a foam box, under the rear seat) is happy with the situation (e.g. no alarms), it energizes the J219 which pulls the connection between 17/87 and 19/30 closed. As a result, when the ignition key is turned from OFF to START, current from the ALWAYS HOT No. 30 bus flows through the ignition switch, through the J219 (Pins 19 to 17), down the black "50A" wire to the "50" terminal on the starter solenoid. The starter solenoid, in turn, energizes the starter motor (which is wired directly to the battery) and presumably, the engine starts.
IF there was an issue with the central locking module or the J219, then it would still potentially be possible to start the engine by removing the "204" J219 and jumpering positions 17 and 19, as shown with this factory jumper from a ROW UrS. A home-made jumper would be 2 spade connectors on the end of about 1.5" of 12 or 14 gauge wire.
So where are the back-up lights in this story? Not sure, maybe on that S3/50A branch. Doesn't matter. What doesn matter is it appears that we have a form of starter interlock/imbolizer that prevents starting if the central locking system isn't happy for any reason.
C4 UrS Central Relay Panel (Under Drivers Knee Bolster ) PN callout
I had previously did a little documentation of the NAmerican UrS4/S6 Central Relay panel (above the Driver's side knee bolster) and knew about the relay in position 4 on that relay panel. (For the automatic cars, it is even labelled the Starter Interlock Relay, i.e. you have to be in Park or Neutral before the ignition switch will energize the starter when the key is turned to START). The question was if the manuals don't have that relay per se but they have a "back-up light" relay, why does it seem to be involved in the starting of an UrS with a manual transmission. I had also documented that some ROW (rest of the world) UrSs did not have the "back-up light" relay but had a jumper instead. Based on the recent thread, I decided to investigate further.
Relay in question is the "204", third from the right:
I first checked the Bentley and found the relay and its connections spread over at least three electrical pages. Hmm..not easy to document. Then I checked the FAQ and found a generic 1996 A6 quattro starter diagram that Nate P. (ImQuattro) had posted. I printed that off and then annotated it based on the Bentley. The result is this:
So based on that diagram, my interpretation is that *IF* the Central Locking/Alarm System control module (on the central locking pump, beside the battery, in a foam box, under the rear seat) is happy with the situation (e.g. no alarms), it energizes the J219 which pulls the connection between 17/87 and 19/30 closed. As a result, when the ignition key is turned from OFF to START, current from the ALWAYS HOT No. 30 bus flows through the ignition switch, through the J219 (Pins 19 to 17), down the black "50A" wire to the "50" terminal on the starter solenoid. The starter solenoid, in turn, energizes the starter motor (which is wired directly to the battery) and presumably, the engine starts.
IF there was an issue with the central locking module or the J219, then it would still potentially be possible to start the engine by removing the "204" J219 and jumpering positions 17 and 19, as shown with this factory jumper from a ROW UrS. A home-made jumper would be 2 spade connectors on the end of about 1.5" of 12 or 14 gauge wire.
So where are the back-up lights in this story? Not sure, maybe on that S3/50A branch. Doesn't matter. What doesn matter is it appears that we have a form of starter interlock/imbolizer that prevents starting if the central locking system isn't happy for any reason.
C4 UrS Central Relay Panel (Under Drivers Knee Bolster ) PN callout
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