igol
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Posts: 3
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Post by igol on Oct 11, 2022 17:28:23 GMT
Applogies but I'm not sure where to look for this.
My Octavia is chucking up an intermittent fault code (P545 on my old basic OBD reader) I've swapped the EGT sensor for new & 2nd hand and it keeps reappearing - the sensors check out when I test them.
I was hoping that OBDEleven would allow me to get a little deeper into the fault find and fix it, but after I connect and run a partial scan when I try to open the control unit to see what its detected it tells me it cant connect, though it will let me clear the fault if I back out and go back in?
Am I missing something very simple?
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Post by dv52 (Australia) on Oct 11, 2022 20:26:50 GMT
igol: Hi. Of course anything is possible - but a very common cause of P545 error is the integrity of the connecting wires/terminals. I assume that you have already considered this! I'm not sure about your module-connect problem - if OBD11 has produced a scan report and if the software allows fault-code clearing, then clearly the device is successfully communicating with the modules. Is the problem only with the one module (ECU?) - can you access other modules correctly? Maybe clear the cache on your mobile/tablet before using OBD11. What model Octavia is this? Don
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igol
New Member
Posts: 3
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Post by igol on Oct 12, 2022 10:30:24 GMT
Thanks for the speedy reply. Yep wires look ok and pull 5v on the multimeter when they should .
It is purely the ECU, I can clear the fault and email the log (shows the 545 error) but while I get into everything else the ECU just throws up the trouble communicating with the control unit. Car itself runs fine though did need the 2nd hand EGT when the DPF kicked in as the fault was blocking a regen and I'm starting to think the ECU itself is the issue and somehow eating the EGTs - plus its listed as a rarely happens fault and as its me it'll be that.
Cache was cleared on my phone just prior to the latest play with it.
Its a mk3 (2015) 4x4 not the Scout, if that helps any? Didnt post in the specific forum as I was thinking it was a more general problem and probably with me Thanks again.
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Post by dv52 (Australia) on Oct 12, 2022 21:31:49 GMT
igol : OK, so Octavia mk3 (2015) has a MQB platform (I suspect)! I'm not sure if you are aware, but when OBD11 is in scan (diagnostic) mode - the software communicates directly with the Gateway module - which then requests that each of the other modules provide a data dump of the contents in their fault memory. On MQB platform cars, the ECU (it's called "J623") is part of the drivetrain CAN bus - so maybe this is the problem (I'm guessing of course). Other modules on the powertrain CAN bus are the airbag module and the auto-trans module. Can these be accessed in the normal way? Again, if the car is operating correctly and if there are no communication errors on the scan report indicating a problem with the ECU talking over the CAN network- this issue appears to be a specific matter related to how OBD11 software is interfacing directly with the hex01 module (only)! Note: when OBD11 tries to access J623 directly, it still uses the Gateway module as an intermediator- but the Gateway module isn't in diagnostic mode. What happens if instead of selecting Home, you select Garage instead? Then select the car - then select Control Units - then select Engine module (@ address hex01). Do you have access to the full suite of OBD11 options for the module?
Don
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igol
New Member
Posts: 3
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Post by igol on Oct 13, 2022 9:57:31 GMT
Thanks again. I'll pretend I understood some of that All the other modules appeared to be fine other than ECU access but I cant say for certain now as I tried the suggested garage way of going in first.
Wierdly its seems to recognise it and allow access, so I came out and went back in the normal way and it worked?? I'm assuming that when the EGT sensor figures are showing they're supposed to stay on screen and not suddenly drop off until you back out and go back in?
I'm thinking when I did the wiring tests it was igntion on engine not running and my intermittant fault may well be a worn wire shorting under engine vibration.
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