1.4 BBY: random stall and buzzing noise

[a-zwo]

Does it crank okay while making the noise? Theory 1 would be that the power steering pump draws a lot of power and maybe pulls the battery down to the point it can’t start (while the pump is running)

As for why it stalls in the first place, it could be a similar thing with a weak battery as mentioned? Or something else is causing the ECU to reset.
I would guess that the pump running is a failsafe and probably the intended functionality if it loses communication with the ECU. If you were travelling at speed and something went wrong, it would be far better to keep the pump running rather than stop it.

 

[Edwrai]

Does it crank okay while making the noise? Theory 1 would be that the power steering pump draws a lot of power and maybe pulls the battery down to the point it can’t start (while the pump is running)

As for why it stalls in the first place, it could be a similar thing with a weak battery as mentioned? Or something else is causing the ECU to reset.
I would guess that the pump running is a failsafe and probably the intended functionality if it loses communication with the ECU. If you were travelling at speed and something went wrong, it would be far better to keep the pump running rather than stop it.

It will crank just fine but will not start, if ignition is turned off and back on will then start fine. The turn over while it’s making the noise is no slower than normal.


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[PlasticMac]

May not be relavant, but on the FSI, a fault in the power steering triggers a limp mode power reduction, via the injectors, for safety as control is compromised. Such an intervention may well prevent starting.
If the engine cranks, then the power steering pump is not drawing significant power. The battery couldn't do both.
I'd suspect the PS Controller
Mac.

 

[Edwrai]

So I was doing other work and tested this today, when the car is running the power steering pump does not vibrate like it does when this fault occurs, no idea what on earth it’s doing. Had a poke around the wiring near the hulk head and back, and no damage that I can see..


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[Sveshais]

Also, the power steering pump is underneath the ABS controller, so it could be that making the noise.

The noise is clearly linked, so identifying that could be quite helpful.

For all of those errors to appear, something quite major is happening, either a short to ground, as mentioned above, or power loss to the ECU. I’m fairly sure no matter what happens to its CANBUS, the ECU should keep running the engine.
The throttle controller is only powered/grounded by the ECU, so the ECU is what’s faulting.

Good point, much appreciated! I had this put aside to see if cleaning the earh connections and fully charging the battery did any good. Today it turned out that it didn't and I got the same issue, but VCDS came up with a couple additional codes I didn't see before:

2 Faults Found:
01314 - Engine Control Module
004 - No Signal/Communication - Intermittent
01314 - Engine Control Module
013 - Check DTC Memory - Intermittent

Will do a thorough check on all the wiring on the weekend, but is there also some diagnostic check I could do for ECU itself?

 

[George Hogg]

Try pulling the ABS and PS fuse individually and see if the noise goes

 

[Edwrai]

May not be relavant, but on the FSI, a fault in the power steering triggers a limp mode power reduction, via the injectors, for safety as control is compromised. Such an intervention may well prevent starting.
If the engine cranks, then the power steering pump is not drawing significant power. The battery couldn't do both.
I'd suspect the PS Controller
Mac.

I also suspect the PS controller


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[a-zwo]

@Edwrai @Sveshais if it happens again, try turning the wheel while the noise is happening (engine off). The pump is just a gear pump, so it shouldn’t be able to make anything other than “normal pump noises”. It does have an over pressure valve in it though. Maybe in this fault state, the pump goes to full speed and the noise is the over pressure valve. If that’s the case, you’ll have very light steering while it’s happening.

@Sveshais which controller are those latest codes from? Guessing not the engine ECU?
If you could post an Autoscan of all modules that would be very helpful

I’m still leaning towards ECU/ECU power. The only way the power steering is connected to the ECU is by CAN and K Line. So the only fault it could create is shorting the CAN and K line to ground/12 volts. As there is the throttle control error, something is going wrong with the ECU when this happens, which would mean Magneti Marelli didn’t protect CAN and K line and allow faults to reset the ECU. I would be very, very surprised if that was the case.

 

[Edwrai]

May not be relavant, but on the FSI, a fault in the power steering triggers a limp mode power reduction, via the injectors, for safety as control is compromised. Such an intervention may well prevent starting.
If the engine cranks, then the power steering pump is not drawing significant power. The battery couldn't do both.
I'd suspect the PS Controller
Mac.

@Edwrai @Sveshais if it happens again, try turning the wheel while the noise is happening (engine off). The pump is just a gear pump, so it shouldn’t be able to make anything other than “normal pump noises”. It does have an over pressure valve in it though. Maybe in this fault state, the pump goes to full speed and the noise is the over pressure valve. If that’s the case, you’ll have very light steering while it’s happening.

@Sveshais which controller are those latest codes from? Guessing not the engine ECU?
If you could post an Autoscan of all modules that would be very helpful

I’m still leaning towards ECU/ECU power. The only way the power steering is connected to the ECU is by CAN and K Line. So the only fault it could create is shorting the CAN and K line to ground/12 volts. As there is the throttle control error, something is going wrong with the ECU when this happens, which would mean Magneti Marelli didn’t protect CAN and K line and allow faults to reset the ECU. I would be very, very surprised if that was the case.

PS controller doenst have Kline only CAN and only able to talk to the cluster, which reports errors on it’s behalf , based on Audi documentation. It’s on the same CAN network as the abs, engine and cluster.

In my case I have changed the ecu and cluster and the problem remains, however I didn’t change them for this reason, it’s very random and can’t be recreated by turning the ignition on and off a few times.

Personally I think it’s the PS pump going mad and fooding 500 baud CAN which it shares with the items above

 

[a-zwo]

Yeah you’re right, I was clearly hallucinating when I checked the SSP.

If you’ve swapped the cluster and ECU it does seem that way.
I originally thought it would want to keep the engine running under all circumstances, but it’s not really dangerous if it stops thinking about it more. Maybe if the CAN bus goes mad it triggers the same kind of failsafe as what happens in a crash, and stops the fuel pump?

Out of interest, did you have the same codes as @Sveshais

 

[Sveshais]

@Sveshais which controller are those latest codes from? Guessing not the engine ECU?
If you could post an Autoscan of all modules that would be very helpful

Sorry, of course, scans attached. There are two: first one done when check engine came up a few days after all codes being reset during the initial earth connection check and battery charge, and another one after the latest stall. Files are named accordingly. No codes were cleared in between, it might help to filter out the unrelated codes as they are quite a few.

 

[Edwrai]

Yeah you’re right, I was clearly hallucinating when I checked the SSP.

If you’ve swapped the cluster and ECU it does seem that way.
I originally thought it would want to keep the engine running under all circumstances, but it’s not really dangerous if it stops thinking about it more. Maybe if the CAN bus goes mad it triggers the same kind of failsafe as what happens in a crash, and stops the fuel pump?

Out of interest, did you have the same codes as @Sveshais

I had very simliar ones, I have changed the ignition relay and it does seem somehow to have improved but has not gone, its very strange, I need to have a poke around under the floor and the earth points.

I get these I believe but not the others

16706 - Engine Speed Sensor (G28)
P0322 - 35-10 - No Signal - Intermittent
18057 - Powertrain Data Bus
P1649 - 35-10 - Missing Message from ABS Controller - Intermittent
18058 - Powertrain Data Bus
P1650 - 35-10 - Missing Message from Instrument Cluster - Intermittent
17953 - Throttle Valve Controller
P1545 - 35-10 - Malfunction - Intermittent

 

[Edwrai]

Sorry, of course, scans attached. There are two: first one done when check engine came up a few days after all codes being reset during the initial earth connection check and battery charge, and another one after the latest stall. Files are named accordingly. No codes were cleared in between, it might help to filter out the unrelated codes as they are quite a few.

Sceshais, do you have an multimeter? Can you measure the voltage on the battery and then measure the voltage from measuring block 4 I think on the engine. With the engine off and on?


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[Edwrai]

FYI battery changed, no difference one in 10 times it will still refuse to start, changing the ignition relay to one I had in a bucket of parts fixed the power steering noise when this occurs however, all very strange, still investigating.

 

[Edwrai]

So a development to this,

When it occurs I can scan the ecu and every module however! This is what the dash looks like, notice no engine lights or epc or any other light except the battery light and the handbrake. It’s almost like the car thinks it’s running!

 

[Edwrai]

Now this is interesting from the Audi self study guide

Power steering sensor G250
The sensor is located in the valve dome of the power-assisted steering box.It records the steering angle and calculated the steering angle speed.If the sensor should fail, the steering function is still guaranteed.The power steering shifts to a programmed emergency running mode. The steering forces required are greater.Error functions are stored in the power steering control unit J500.

I think I'm going to give changing the pump a go as this sensor is inside the pump.

 

[Joga]

Now this is interesting from the Audi self study guide

Power steering sensor G250
The sensor is located in the valve dome of the power-assisted steering box.It records the steering angle and calculated the steering angle speed.If the sensor should fail, the steering function is still guaranteed.The power steering shifts to a programmed emergency running mode. The steering forces required are greater.Error functions are stored in the power steering control unit J500.

I think I'm going to give changing the pump a go as this sensor is inside the pump.

Actually, the G 250 is mounted in the bottom part of the steering rack, not in the pump. It was also only there for the early cars.

 

[Edwrai]

Actually, the G 250 is mounted in the bottom part of the steering rack, not in the pump. It was also only there for the early cars.

Thanks Joga I have also discovered this with further research.

I did find that pulling fuses when this occurs can wake up the ecu so something strange is going on here.

I’m currently leaning towards just changing the unit as I have a spare, just so I can discount it, however it may only be a symptom and something else is failing the ecm to not communicate.

This only occurs sometimes, once the car is started there are no issues, and it normally only requires one ignition off and then to try to start the car again.


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[PlasticMac]

I thought the same, that it was replaced by the steering angle sensor on later cars, so I looked at the wiring schematic, and it's there, with no note about it being phased out, as is the case with other mods that came during production. The circuit symbol doesn't look like an angle sensor to me.
Could it still be there, but slight change in function?
I did wonder how it did what the SSP says it did.
Mac.

 

[Edwrai]

I thought the same, that it was replaced by the steering angle sensor on later cars, so I looked at the wiring schematic, and it's there, with no note about it being phased out, as is the case with other mods that came during production. The circuit symbol doesn't look like an angle sensor to me.
Could it still be there, but slight change in function?
I did wonder how it did what the SSP says it did.
Mac.
View attachment 123780

What year is this wiring diagram from, also I wouldn’t always trust these I’ve worked with a lot of VAG wiring diagrams and they are often always 100% accurate.