That error is related to the other issue I posted about; "ACC and Audi braking guard: Unavailable" where you suggested a corroded antenna is at fault. I will put a months wages on these two issues being unrelated.
I can say with a good degree of certainty that it's not ABS (ie. braking effect) causing the problem.
That error is related to the other issue I posted about; "ACC and Audi braking guard: Unavailable" where you suggested a corroded antenna is at fault. I will put a months wages on these two issues being unrelated.
I can say with a good degree of certainty that it's not ABS (ie. braking effect) causing the problem.
I can take that bet and tell you for certain that ACC and ABS are definitely related. I can also bet for certain ABS could be causing this issue if the module is failing. How much do you want to bet and whos holding the money?
Looking back at this I would be curious if perhaps something was damaged during control arm replacement like a wheel bearing or if the bearing itself is corroded but I would think an abs light would be present or shown. Based on what I see I would try disconnecting abs unit and drive the car see what it does. NOTE vehicle will not have ABS function so if you can't drive to save your life drive with extreme caution.
Sorry I think there's crossed wires here (not literally).
1) The ACC and ABS are related, yes, but that's not this problem. That's the one with the "ACC and Braking Guard unavailable" message - where you suggest there's corrosion in the roof aerial.
2) But this lurching issue is separate. The car is lurching under sudden acceleration, especially at low speed, and I don't believe it's an ABS issue.
I have learned here on this forum that regarding the Network / CanBus system , especially with this sophisticated model Audi, engine performance issues can be caused by just about anything!
Are you aware of the engine motor mounts problem fault (can-bus connected) on a a5/S5 can cause all sorts of engine related issues . Not all failing engine mounts will do this on every S5, but many have and were the last thing a diagnostician thought of.
A motor mount causing severe misfires and running issues...... what!
I have learned here on this forum that regarding the Network / CanBus system , especially with this sophisticated model Audi, engine performance issues can be caused by just about anything!
Are you aware of the engine motor mounts problem fault (can-bus connected) on a a5/S5 can cause all sorts of engine related issues . Not all failing engine mounts will do this on every S5, but many have and were the last thing a diagnostician thought of.
A motor mount causing severe misfires and running issues...... what!
All audi's the newer they are the more integrated the systems are and have an absolute need to talk to each other. This is why when one thing fails a Christmas tree comes on the dash because 5-8 systems all talk to each other reading data and inputs and outputs from each other to make the necessary calculations to ensure the most safe and comfortable conditions during driving. They are giant computers on wheel like most vehicles these days but far most sophisticated than anything else on the road if you ask me. Domestic vehicles are at least 15years behind audi, jap imports probably about 10 years.
When the problem happened a huge number of warnings appeared and it generated this log below. The new issues were to do with; MAF sensor / 02 Auto Transmission / 03 ABS Brakes / 10 Park & Steer assist / 13 Auto Distance / 34 Level Control (air suspension) / 54 Parking Brake / 8B Adaptive Cruise / 8E Image Processing.
I'm not sure why you have a MAF fault (though I have a guess) but the rest of the drama traces back to the MAF fault.
Here's your April auto-scan, cut down to the bits involved in your trouble/event that I find most interesting:
Code:
Address 01: Engine (J623-CTNA) Labels:. 07P-906-023-V1.clb
5668 - Mass Air Flow Sensor (G70)
P0101 00 [00100111] - Implausible Signal
Not Confirmed - Tested Since Memory Clear
Freeze Frame:
Date: 2025.04.02
Time: 09:09:32
Engine speed: 3893.00 /min
Normed load value: 96.9 %
Voltage terminal 30: 13.028 V
Address 02: Auto Trans (J217) Labels:| 0BK-927-156.clb
2505 - Torque Management Feedback Signal A
P2637 00 [00100111] - -
Not Confirmed - Tested Since Memory Clear
Freeze Frame:
Date: 2025.04.02
Time: 09:09:35
Voltage terminal 30: 14.051 V
Address 03: ABS Brakes (J104) Labels: 4H0-907-379.clb
0172 - Function Restriction due to Faults in Other Modules
U1113 00 [10001001] - -
[Can_Motor_03_QBitMotormomente]
MIL ON - Confirmed - Tested Since Memory Clear
Freeze Frame:
Date: 2025.04.02
Time: 09:09:33
Address 10: Park/Steer Assist (J791) Labels:| 4H0-919-475-7X5.clb
13637413 - Databus
U1123 00 [00001001] - Received Error Message
[Bremsensteuerger t - ESP_01.ESP_Systemstatus - Fehlerspeicher auslesen]
Confirmed - Tested Since Memory Clear
Freeze Frame:
Date: 2025.04.02
Time: 09:09:33
Address 13: Auto Dist. Reg (J428) Labels:| 4H0-907-561.clb
105472 - Function Restriction due to Faults in Other Modules
U1113 00 [00001001] - -
[FAULT_CIS_VDC_FAIL]
Confirmed - Tested Since Memory Clear
Freeze Frame:
Date: 2025.04.02
Time: 09:09:33
Voltage terminal 15: 14.522 V
Address 34: Level Control (J197) Labels:. 4G0-907-553.clb
0648 - Function Restriction due to Implausible Message(s)
U1112 00 [00001001] - -
Confirmed - Tested Since Memory Clear
Freeze Frame:
Date: 2025.04.02
Time: 09:09:33
Address 53: Parking Brake (----) Labels: 4H0-907-801.clb
464384 - Function Restriction due to Faults in Other Modules
U1113 00 [00001001] - -
[FC_SIGNAL_MO_QBIT_MOTORMOMENTE_QBIT]
Confirmed - Tested Since Memory Clear
Freeze Frame:
Date: 2025.04.02
Time: 09:09:33
Voltage terminal 30: 14.5 V
Address 8B: Adaptive Cruise 2 (J428) Labels:| 4H0-907-561.clb
105472 - Function Restriction due to Faults in Other Modules
U1113 00 [00001001] - -
[FAULT_CIS_VDC_FAIL]
Confirmed - Tested Since Memory Clear
Freeze Frame:
Date: 2025.04.02
Time: 09:09:33
Voltage terminal 15: 14.503 V
Address 8E: Image Processing (J851) Labels:| 4H0-907-107-V2.clb
0028 - Function Restriction due to Faults in Other Modules
U1113 00 [00001001] - -
[ESP_ESP_01_Signal_Error]
Confirmed - Tested Since Memory Clear
Freeze Frame:
Date: 2025.04.02
Time: 09:09:33
Voltage terminal 15: 14.6 V
The ECUs calculate how much torque the engine is producing based on air mass and injected fuel mass. If the MAF fails, it has to kind of guess to run the engine. The engine's current output torque is continuously broadcast (via CAN/FlexRay) along with a single bit flag (Qualifizierungsbit, or Q-bit) that tells receivers if that value is considered reliable. If you've ever read VW/Audi SSPs and looked at the logical diagrams for how sensors A/B/C are used to do task X, and if sensor B fails the module uses a substitute/calculated value, the Q-bit is one of the ways downstream modules know to switch to their substitute calculation.
In your scan, as a first (known) order effect, the ECUs think one of the MAF readings isn't legit, and starts doing the guessing thing.
As a second order effect, the transmission, ABS/ESP, and parking brake need to know current engine torque to do their jobs properly, they see that Q-bit set, so they fault out.
As a third order effect, all your driver-assistance and comfort stuff needs a healthy ABS/ESP to do their jobs properly, and the ABS/ESP is faulted out, so they join the party.
I'm not sure why the MAF was kicked out, but it's interesting you have that frequent electrical fault with one of your O2 sensors, though it doesn't appear in this particular scan. I think it's also interesting, out of the modules that report control module voltages in their DTC freeze-frames, there is a *considerable* spread.
Code:
Address 01: Engine (J623-CTNA) Labels:. 07P-906-023-V1.clb
Voltage terminal 30: 13.028 V
Address 02: Auto Trans (J217) Labels:| 0BK-927-156.clb
Voltage terminal 30: 14.051 V
Address 13: Auto Dist. Reg (J428) Labels:| 4H0-907-561.clb
Voltage terminal 15: 14.522 V
Address 53: Parking Brake (----) Labels: 4H0-907-801.clb
Voltage terminal 30: 14.5 V
Address 8B: Adaptive Cruise 2 (J428) Labels:| 4H0-907-561.clb
Voltage terminal 15: 14.503 V
Address 8E: Image Processing (J851) Labels:| 4H0-907-107-V2.clb
Voltage terminal 15: 14.6 V
Voltage is relatively consistent for everything that *isn't* engine and transmission, and engine is the lowest. Strictly guessing, but you might have a bad engine ground that's losing contact when you get into the throttle and the drivetrain shifts a little bit. Or, that O2 sensor that's frequently faulting could be intermittently shorting to ground due to that same drivetrain shifting and dragging down everything else.
My own next steps would be to find some terminal 15/terminal 30 voltage measuring values in the ECUs to log, and see if they jitter around during your trouble events. You could also use a multimeter to check for nonzero voltage potential between the engine block and a good chassis ground while at standstill, and *carefully, with an assistant* see if you can trip the problem at standstill applying some throttle while holding full brake. If the results look interesting, run an extra ground from the engine to the chassis and retry. You can also try just unplugging the frequently-faulting O2 sensor. You can leave it installed in the cat converter, just unplug the connector which should be easily reachable. That'll make the engine run open-loop, you'll have a bunch of faults and the trans may not shift smoothly, but as a diagnostic measure you can see if that makes the jerk/stumble go away.
TL;DR: Don't Panic, figure out the engine electrical issue and the rest will follow.
Thankyou VERY much for the detailed reply!!! Initial comments are;
You mention they are in an order of effect. Is it just a coincidence that the numbers are for modules in ascending numerical order?
The fault with the oxygen sensor didn't show in that scan because it's intermittent and hadn't appeared while I was collecting that data. I do plan to replace it, maybe even do it myself because it looks relatively easy to reach so it might be fairly easy to pull the plug off for testing purposes, as you suggest.
The point about movement in the transmission potentially making or breaking an electrical contact is an interesting one. I have posted in the A8 Parts Forum to get the correct part numbers for (2x) engine mounts and (3x) gearbox mounts, as I think that might be causing an issue. I say that because I KNOW they have been stressed - because when the problem first appeared it was due to closed valves in the exhaust and the gasses having nowhere to go (long story as to why that happened but it was my fault for wanting the damned thing modified in the first place) and I had to disconnect the actuators to keep the flaps open - I'm having the final touches done this week to be able to plug them back in, having physically bypassed the flaps with further exhaust mods. But at the time when the flaps shut and I gave it some throttle, the lurching nearly put me through the window. So yes they've had some stress, maybe even some shearing has happened. Perhaps changing them will make this problem go away.
Logging the output of the ECU - can you or anyone else help with exactly what the parameter names are within the software please? The last time I used it I didn't think that the sampling resolution was all that great either - from the top of my head about 300ms per sample maybe...
Thanks @Dr Sheldon much appreciated. I called ADS, they are certainly willing to take a look. So I'll get the final bits of the exhaust completed tomorrow, the guy who is helping me is a very good mechanical engineer so I'll run a few things past him while I'm there too.
The point about movement in the transmission potentially making or breaking an electrical contact is an interesting one. I have posted in the A8 Parts Forum to get the correct part numbers for (2x) engine mounts and (3x) gearbox mounts, as I think that might be causing an issue.
I say that because I KNOW they have been stressed - because when the problem first appeared it was due to closed valves in the exhaust and the gasses having nowhere to go (long story as to why that happened but it was my fault for wanting the damned thing modified in the first place) and I had to disconnect the actuators to keep the flaps open - I'm having the final touches done this week to be able to plug them back in, having physically bypassed the flaps with further exhaust mods. But at the time when the flaps shut and I gave it some throttle, the lurching nearly put me through the window. So yes they've had some stress, maybe even some shearing has happened. Perhaps changing them will make this problem go away.
It's certainly possible. If your jerking on sudden accel is pretty repeatable, just for S&Gs you might try finding a big empty parking lot and doing some sudden accel in Reverse. Might not learn much if the problem still happens, but if it *doesn't* happen, that would reinforce the idea the driveline shifting is involved.
Logging the output of the ECU - can you or anyone else help with exactly what the parameter names are within the software please? The last time I used it I didn't think that the sampling resolution was all that great either - from the top of my head about 300ms per sample maybe...
Not really sure, there will be different naming for different engines, and there will probably be several values available. Just use the advanced measuring values function to scroll through and look for voltages, or use the search function with keywords like "voltage" or "terminal", etc.
Thanks @Dr Sheldon much appreciated. I called ADS, they are certainly willing to take a look. So I'll get the final bits of the exhaust completed tomorrow, the guy who is helping me is a very good mechanical engineer so I'll run a few things past him while I'm there too.
You've crossed out your VIN, if you share it, I can look up your mount part numbers in PL24.
It's certainly possible. If your jerking on sudden accel is pretty repeatable, just for S&Gs you might try finding a big empty parking lot and doing some sudden accel in Reverse. Might not learn much if the problem still happens, but if it *doesn't* happen, that would reinforce the idea the driveline shifting is involved.
Not really sure, there will be different naming for different engines, and there will probably be several values available. Just use the advanced measuring values function to scroll through and look for voltages, or use the search function with keywords like "voltage" or "terminal", etc.
I've ordered a pair of new air filters too. I don't know if they've been changed as all the Audi service history I have only relates to oil & spark plugs. It made me think when @jyoung8607 mentioned the MAF sensors. So, they're cheap enough and I can probably change them myself. So, why not.
Thinking about it, how do I get a copy of all the work which Audi has done on the car? My local dealer tend to ignore requests like that.
