Starter motor relay

[Sealti96]

Does any one know the exact location of the starter motor relay on a B8 A4 ??

I'm also looking for the starter/ignition switch wiring diagram.

I have tried searching forums, YouTube and Google and can't find any definitive answers.

Any help would be greatly appreciated.

[Smac770]

fuse/relay panel B, the one in the ECU box, under the wiper fluid funnel in the plenum chamber. Should be the second from the car right side end in the row of relays.

[old guy]

Clicky click®

[Sealti96]

Thank you !! Would happen to know the number on it??

My car has a small black relay that says 404 on it in that location. Just want to make sure.

My car was having starter issues so I went and replaced the starter but now the starter is not getting a signal.

Its not the stater because I energized the starter solenoid directly and it cranks but once I connect the signal wire on the car and hit the start button nothing happens.

[Sealti96]

I'm suspecting that the relay or something else got damaged in the process.

[Sealti96]

Think you sir.

[Smac770]

The documentation is confusing. It refers to dual relays, J53 and J695, and then says both relays are in the same spot.

power to the whole situation starts with:
term 15 12v -> fuse panel C, row 1, fuse 16 (40A) -> ECU box plug T17r (the white one) pin 15

this pin 15 then connects to a variety of things:

B8.0 CAEB starter relay circuit.png

So the 12v comes in, passes through two ECU controlled relays, then goes out "T5l pin 1" to the starter. It never explains where this T5l is. The other four pins appear to be related to the coolant fan control module.

So you'd want to test for ground from the two ECU control pins when you're trying to start the car, as well as see how far the 12v makes it.

Getting in that box is such a pita, or I'd look at my '09 to see what's what with that relay(s).

https://nemigaparts.com/cat_spares/e...q/636u/937200/
Unfortunately, ETKA does seem to help other than supply the possible part numbers. Doesn't say which one you should actually expect as the starter relay(s).

[Smac770]

https://forums.quattroworld.com/a5/msgs/7356.phtml

Ok, so there actually are two relays in that B spot. Both "404" marked in the linked example.

So 7M0951253C, now replaced by 4H0951235C
https://parts.audiusa.com/p/Audi__/6...M0951253C.html
https://parts.audiusa.com/p/audi__/R...H0951253C.html

Interesting that they are SPDT rather than SPST; the de-energized output, pin 4, is unused in this instance but it'll be 12v hot anytime the car is on.

[whats77inaname]

My car was having starter issues so...

Can you expound on that a bit?

The reason I ask: https://www.audizine.com/forum/showt...A4-won-t-crank

While I was going through that mess, I was told by more than one Audi tech that the starters on our cars rarely fail.

[Sealti96]

For a few months the car would intermittently fail the first start attempt but would always start on the second attempt.

But last Friday the starter was sounding extra tired and smelled like fried circuit inside the car but the car started but later that night it finally died.

I would press the srart buttom and nothing would happen, no clicking or nothing.

So I took out the starter and did a bench test on it and indeed was fried.

[Sealti96]

The documentation is confusing. It refers to dual relays, J53 and J695, and then says both relays are in the same spot.

power to the whole situation starts with:
term 15 12v -> fuse panel C, row 1, fuse 16 (40A) -> ECU box plug T17r (the white one) pin 15

this pin 15 then connects to a variety of things:

B8.0 CAEB starter relay circuit.png

So the 12v comes in, passes through two ECU controlled relays, then goes out "T5l pin 1" to the starter. It never explains where this T5l is. The other four pins appear to be related to the coolant fan control module.

So you'd want to test for ground from the two ECU control pins when you're trying to start the car, as well as see how far the 12v makes it.

Getting in that box is such a pita, or I'd look at my '09 to see what's what with that relay(s).

https://nemigaparts.com/cat_spares/e...q/636u/937200/
Unfortunately, ETKA does seem to help other than supply the possible part numbers. Doesn't say which one you should actually expect as the starter relay(s).

This is great info!! I really appreciate it.

Would you happen to have a diagram of the ignition switch/start botton?

[Smac770]

All the wiring diagrams are in a document, along with all the other repair documents, on erwin.audiusa.com
The key slot and adv key start/stop button are not tied to the J623 or the starter directly. They are connected to various other modules, which all talk via CAN bus, including to the J623 ECU. It's the J623 ECU that invokes the starter by grounding those two control lines to the relays, which then passes 12v to the starter.

[whats77inaname]

For a few months the car would intermittently fail the first start attempt but would always start on the second attempt.

But last Friday the starter was sounding extra tired and smelled like fried circuit inside the car but the car started but later that night it finally died.

I would press the srart buttom and nothing would happen, no clicking or nothing.

So I took out the starter and did a bench test on it and indeed was fried.

Ah, I see. Thank you for extrapolating

[Sealti96]

Guys I think this problem might be past my level of experience, I sent the car off to my friend's autoelectric shop to be diaognosed. I will keep this thread updated until the problem is solved.


Thanks for all the feedback!!

[Sealti96]

Car is up and running once again. ($400 later) Luckily my friend owns the shop, sure an Audi shop would charged me way more.

ECM was fried (APR stage 2 flashed)

Turns out that the first rebuilt starter was built wrong, the starter solenoid was rotated away from the engine causing the main positive terminal to touch the motor mount bracket which I didn't notice at first. When I connected the battery I saw a kinda hard spark right there I knew something was wrong so refrained from connecting the battery and went back to check the starter I bought from advanced auto (big mistake).

I got a different starter which had the right clocking on the solenoid terminals, installed it and everything came together very easily then I went and connected the battery (no hard sparking this time) but when I went to start the car I noticed the check engine light and esp light flashing and the car would not crank or start.

Something else I noticed was that the cooling fans start running as soon I would press the on button which is when I knew I screwed up big time.

I know some guys are asking themselves why I was asking about a starter relay/diagram and the reason is that I didn't know that the starter signal runs through ECM first, all the cars I used to working you can completely unplug the ECM and the starter would work even if the car didn't start.

I hope someone can learn from my lack of Audi mechanical knowledge even though I'm a very mechanically inclined individual.

But honestly I blame Advance Auto for not having good quality control with the re-builders.

[Sealti96]

I am not even exaggerating when I say it took about 1 sec to damage to the ECM.

[Shabayaba]

Hi I’m looking to fix my crank no start issue with my 09 Audi s5