A6 2010, CAHA ENGINE, Aut.

[Daniel.augustsson]

Good evening! A question, has two error codes and an Audi A6 -2010 that does not start. It came on suddenly after changing the xenon bulb (accident?) anyone have any ideas about the below?

When a friend helped me read the error codes, there were a lot of communication errors. These do not come now. After some digging in the car, we now have 2 fault codes, a U111300 (function limitation due to received message, permanent) which cannot be deleted, and a P305300 (starter motor control, return measurement, short circuit to ground/interruption -permanent. The latter is deleted temporarily, but returns when I drive with the starter motor. It should be added that the starter motor does not make its own attempt to start when I release the key, without me must hold the key in the right position to run the start.All inputs are welcome!
//Daniel

[Smac770]

CAHA, so 2.0 TDI. So not 2.0 TFSI, which is what this forum is for.

MY10 A6, so C6.5. That's probably the forum to really post this in, since you have more of an electrical issue than an engine issue, based on the description. https://www.audizine.com/forum/forum...5-C6-A6-S6-RS6


"the starter motor does not make its own attempt to start when I release the key, without me must hold the key in the right position to run the start"? I assume this means you can't just turn the key to start position and release it and the engine will start up. You have to hold the key in the start position until the engine has ignited, and then you can release the key to the run position?

It appears the C6.5 uses the same J53 + J695 starter relays pair like in the MLB vehicles (B8, C7, D4). This "term 50" voltage output from the starter relays, it goes to the starter solenoid, and to a pin on the ECM. This is how the ECM confirms when the starter is being activated to spin; and the ECM can know if the engine is actually spinning via the engine speed sensor aka crank position sensor.

And the ECM controls the activation of both of the two starter relays.

I assume your P3053(00) code means the ECM control (of the relays) or monitor (of term 50 voltage) has failed in some manner. Common first step would be to swap out the relays and see if anything changes.

The ECM pins are not the same as my B8.0, the specific fuse references are obviously not going to be the same, and the relays are not the same as mine (which are a pair of 404s in the ECM box), but this is the general architecture you're working with:

B8.0 CAEB starter relay circuit.png

B8.0 CAEB starter relays pinout.jpg

Looks like the relays are under the dash behind the headlight switch on a C6? https://youtu.be/T32sNntKFN8?t=438 At that moment in the video, he's looking at the relays panel. The J53 is the right most cube in the top row. The J695 is the cube to the left of the 404 pair in the lower row. The control lines from the ECM to the relays pass through the 17-pin red connector in the ECM box, pin 4 (to J695) and pin 5 (to J53).

So between all that, you should be able to sort out something. Most likely the relays are just flaking out; known to happen eventually. Or you might have corrosion in the wiring connections somewhere, or maybe that 17-pin red is not connecting well (just disconnect and reconnect it). Can't say until you get in there and start assessing.

[Daniel.augustsson]

Hello. I have now measured the continuity between the relay and the pin on the ecu, it was ok. and the relays to. I have also measured the voltage into the ECU pin (85 on my ecu), and I have voltage there when i run the starter . I am starting to think that the error is in the ECU, what do you think? I have also measured the voltage on the injectors when the starter is running, it is 0v. I believe that the ecu has broken down and therefore cannot continue the sequence of start-ups. I would lbe happy for more inputs!

Daniel

[Smac770]

ECM malfunction is always a possibility.

[Daniel.augustsson]

Hello again. Do you think there are other possible causes? What could it be? Daniel

[Smac770]

https://www.audiworld.com/forums/a6-...-crank-2876610

In that instance, guy said it was the wire from starter relay output (term 50) to the monitor pin on the ECM. But if you're saying the wire at the ECM that is the term 50 monitor wire shows 12v when the starter is running, it would seem the only thing left is the ECM itself.

As for the U1113, no way to know without a full VCDS autoscan log posted.

[Daniel.augustsson]

Hello again. Sorry for asking more questions, but have a question I would like an answer to. The cable to the ECU is branched on the wire between the starter relay and the solenoid. Do you know where? I'm starting to think that the insulation is bad and want to temporarily replace it with a temporary one. But I have to link it with the wire to the ECU. Another question, if I measure between the solenoid + and ground, what ohm value should I have there? Thanks in advance!

[Smac770]

I don't know specifically on a C6. But it appears it'll be in the ECM box.

The black/red term 50 output wire leaves from the J53 starter relay plate and runs to the red 17-pin connector in the electronics box in the plenum chamber (ie, where the ECM is located), pin 16. After passing through that pass-through connector, the large wire carries on to the starter. Somewhere shortly after the 17-pin, the smaller wire from the ECM is spliced to that larger wire. It may well be the smaller wire is crimped in with the larger wire at the 17-pin. Don't really know.

That splice point is referred to as "D97, connection (50) [ie, term 50] in right engine compartment wiring harness". But I don't know if there's some reference to look up where D97 is physically located.

https://audi.7zap.com/en/rdw/audi+a6...AHA_diesel_4_2

That's the engine harness for a C6.5 CAHA. The 17-pin red is item [7]. The ECM connectors are items [2] and [3]. The 1-pin to the starter is item [23], this passes the term 50 through from the engine harness to the starter harness. I wouldn't be surprised if the spice of the small wire from [2] or [3], whichever connector it's on, to the large wire between [7] and [23] to be there where the wires comes together before [4]. But can't validate that.

It also seems the 17-pins are "across the plenum chamber" on the left side if you're LHD drive, while the ECM is always on the right side? Don't know the C6 stuff. Don't know on the starter solenoid resistance. It appears from google search that 0.4 Ω to 2.0 Ω is typical.

[Daniel.augustsson]

Hello again! I really appreciate the time you took to help me. I have changed the starter as I thought it could be the one, but no. There is a capacitor at the ecu, do you know what it does? (C24?) I'm also thinking about where relay j329 is located, and what it does. Thanks in advance! Daniel

[Smac770]

That's the AC suppression cap. Being a cap, it's an open circuit to DC and a short circuit to AC. So any AC that somehow gets generated in the car electrical (likely by the alternator) is grounded out.

J329 is the term 15 relay. As I've posted, if you measure 12v at the starter relays output (term 50), that originated from the term 15 at the starter relays input. So not likely the issue.

That sideways picture hurts my neck. You see it draw what I've already drawn. Term 15 into J695, the output of which feeds into J53, the output of which goes to the starter solenoid. The branch at D97 is the line that goes to the ECM so the ECM can validate the starter solenoid voltage is active.

The control side of the starter relays, you see both are connected to the term 15. And the ECM grounds the other side of each to activate the relay.

[Daniel.augustsson]

Hello again. I soon go crazy. Do you know how the start sequence works with relay, solenoid, ecm? The car starts when I hold the key clockwise, but if I pull to the right and let go, the car tries to start for a second, then nothing happens. At that moment, I get the message P305300. I'll soon have to hand in the car and be ruined :(

[Smac770]

I mean, if it's like every other turn-the-key-to-start car I've ever been in, you have to hold the key in the start position until the engine fires up, then you release the key and it springs back to the run position.

https://ownersmanuals2.com/d/71210/a...-owners-manual
page 109 (111 in the PDF), unfortunately, it fails to elaborate if you should have to hold or not hold the key upon turning it to the start position.

Does the car start fine if you hold the key in the start position until it starts and then release it? Or does it also cut out the cranking after a second even while you hold the key in the start position?

[Daniel.augustsson]

My car is special, it has both key start and start/stop button. We think it went wrong when it was ordered :) The car makes a start attempt when I turn the key clockwise and releases, however, it does not start. Nor does it start with a quick press of the start button. If, on the other hand, I hold the key clockwise, or the start button, it starts. I still have error code U111300 that cannot be deleted, as well as P305300, which can be deleted, but returns after every start/start attempt. I have bought a used ecu that I got today, and a friend is going to clone it tomorrow. Then we'll see :(