S-Prihadi

Sharing....

Glitch ( technical ) according to Wiki : https://en.wikipedia.org/wiki/Glitch

Car last engine use was 20th March 2022 evening. 35,220KM there then and until now 25th March, I have not started the engine.
21st March I was doing 2nd time work on my DOWNshift button, by 22nd March I scanned the car and clear all codes.

23rd March late afternoon till pass midnight I was playing around with smoke test machine at my intake system and inspecting my Bank 2 turbo diverter valve.
Removing the 2-wire connector to the turbo diverter valve surely would trigger a DTC, ECM will declare short circuit or mailfunction, as expected.
Engine never get started still at this point, except ignition key cycling many times for the day to Ignition ON/OFF for scanning purpose and to remove DTC.

Here is the first time a driver seat related DTC appeared.





The weird part is not the DTC, but the declared mileage of 35,216KM of the CURRENT DTC its like time travel to 4 kilometers ago.
At 35,220KM when I cleared DTC related to my DOWNshift switch at the steering, there was no N32/1 driver seat DTC.

I know an N32/1 driver seat need to talk to N80 steering column module for the memory seat function, because telescopic and steering height is part of the seat memory.
That is all I can think off. Still this does not explain why 4 kilometers difference in the reporting, assuming my work on the N135 steering wheel switch interface is part of the N80 Steering Column.

This is not a first time I seen a few kilometers ago DTC apprearing at current kilometers/mileage, at which the car was completely scanned and cleared of all DTC at the current mileage at least 1 or more days ago.
Can a module developed amnesia and then few kilometers and days later recovered and produced a better-late-then-never DTC ?

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I also notice how false DTCs can be triggered.
When we disconnect battery to do some work, the state of how deep sleep the car modules are at the time of the disconnection does matter to potential false DTC
appearing later when battery cable re-connected. A stored/historical DTC usually, but sometime can be CURRENT.

I think it is about either different boot time upon power/battery coming back online for different modules or different speed of dead state of the module when power or battery disconnected.
This is for software expert to assist.

Since all modules communicate via CAN BUS, any module being offline can create DTCs for itself and other connected modules reporting issues they have with the offline module.
I learnt this when I was cataloging my Front SAM fuse asignment and what DTC appears when each and every fuse get removed.

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So, for software expert in the house. Why and how a 4KM ago DTC can appear out of nowhere, albeit its been scanned a few times previously ?

Thank you...

S-Prihadi

Below is an example of a DTC caused by battery disconnect/re-connect and wrong way of draining the left over power at the module/s.

To speed up battery drain when I first disconnected the battery, within like 1 minute , *I turned Ignition ON and did a crank/start. ( * not a good idea.)
This is for the 2nd time I was messing around with my DOWNshift pedal button.

When job done, got the battery connected and scanned the car : 3 DTCs and 2 being CURRENT. Ignore the alternator one.

Remember the P261029 DTC from N3/10 engine computer, I shall discuss it after the A80 module.


A80 Shift Module (ISM) module reporting DTC.




Notice both DTCs above for its voltages and reported temperature of the A80 module.



Back to P261029 DTC from N3/10 engine computer. This is MB specific DTC. First digit after P, if 1 or 2 or 3 and not ZERO, it is manufacturer specific DTC. Zero is OBD 2 standard.
This is an interesting DTC, because there is a little extra explanation for it, albeit not related to my engine computer https://static.nhtsa.gov/odi/tsbs/20...76663-9999.pdf
Probably this link is not guaranteed for Mercedes specific, but it does explain P261029 better than Xentry : http://zatonevkredit.ru/repair_manua...0000019RQA.xml

I say it is interesting when I read the Russian link mentioning : The soak timer operates after the ignition switch is turned off. When a certain amount of time has elapsed after turning the ignition switch off, the soak timer activates the ECM to perform malfunction checks which can only be performed after the engine is stopped. The soak timer is built into the ECM.
....... because 2 days ago while I was inspecting my turbo diverter valve, I on purpose did extended monitoring on the signals from ECM for diverter valve ( 12 Volt ) and the MAP sensor ( 5V ) after ignition OFF and
FOB key kept away at a distance.

The ECM sent out diagnostic voltage/signal to verify sensors are connected or healthy : Red is the MAP sensor at constant +3 volt and blue is the turbo diverter valve getting pulsing signal 0.6 volts plus and minus.



I know by amperage load, my car modules eating 10-12 amps during a door opening and down to 9amps and then 6 amp-ish is a sign of modules, I mean plenty enough modules waking up.
However, I never knew that with ignition key out of car and door locked by remote control of key FOB, ECM is still sending diagnostic signals to its sensors like for 2 minutes or so and it is not a constant signal.
Some signal can be 10 or 20 seconds long or longer in between the "micro sleep".

I do not need the car key FOB close by, my engine computer will send diagnostic signals to its sensors simply by me trying to open the locked door.
I guess the Keyless Go sensor or perhaps the mechanical pull of the door handle ? See below :

When I touched + pull the locked door handle. Below is 9 seconds for turbo diverter valve and 30+ seconds for MAP sensor. I stopped logging by page 6. 1 page is 5 seconds long.



Door open or key in slot ..... only in slot without turning even 1 click to ACC1, ECM will send the diagnostic signals.


So , do not be scared looking at weird DTCs ( note them to learn ) appearing when scanned, if you disconnect any engine sensors with key out of Ignition hoping ECM won't wake up.
The same goes for battery connect and disconnect.
Well, this is also the reason most members when advising unknown/weird out of the blue DTC for new members, among others is : FIRST ...make sure your battery is good and best fully charged.