W166 ISM stops working
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W166 ISM stops working
i have a w166 mercedes body where the ISM stops working about 15 mins after starting the car
when first started the car shifts normally between gears but about 15 mins in the shifter stops working
i have ran a few diagnostics and found communication errors with the ISM module, so the first thing i did was check the CAN buses under the passenenger floor for any water damage, i did not find any and all CAN buses seem normal
i have replaced the steering column module and that proved of no use, at the same time i entered the datastream for the DIRECT level position and found that it gives off correct data when moved (park, drive, etc) but the car itself does not shift
the car has 20K KM milage on it thats what i havent replaced the ISM itself as i believe its unlikely for such problem to be caused by the ISM itself
has anyone ran into a similar problem and found a solution?
thanks everyone in advance
when first started the car shifts normally between gears but about 15 mins in the shifter stops working
i have ran a few diagnostics and found communication errors with the ISM module, so the first thing i did was check the CAN buses under the passenenger floor for any water damage, i did not find any and all CAN buses seem normal
i have replaced the steering column module and that proved of no use, at the same time i entered the datastream for the DIRECT level position and found that it gives off correct data when moved (park, drive, etc) but the car itself does not shift
the car has 20K KM milage on it thats what i havent replaced the ISM itself as i believe its unlikely for such problem to be caused by the ISM itself
has anyone ran into a similar problem and found a solution?
thanks everyone in advance
Out Of Control!!
Joined: Sep 2018
Posts: 14,666
Likes: 4,568
From: unbegrenzt
2017 GLE350 4MATIC
i have a w166 mercedes body where the ISM stops working about 15 mins after starting the car
when first started the car shifts normally between gears but about 15 mins in the shifter stops working
i have ran a few diagnostics and found communication errors with the ISM module, so the first thing i did was check the CAN buses under the passenenger floor for any water damage, i did not find any and all CAN buses seem normal
i have replaced the steering column module and that proved of no use, at the same time i entered the datastream for the DIRECT level position and found that it gives off correct data when moved (park, drive, etc) but the car itself does not shift
the car has 20K KM milage on it thats what i havent replaced the ISM itself as i believe its unlikely for such problem to be caused by the ISM itself
has anyone ran into a similar problem and found a solution?
thanks everyone in advance
when first started the car shifts normally between gears but about 15 mins in the shifter stops working
i have ran a few diagnostics and found communication errors with the ISM module, so the first thing i did was check the CAN buses under the passenenger floor for any water damage, i did not find any and all CAN buses seem normal
i have replaced the steering column module and that proved of no use, at the same time i entered the datastream for the DIRECT level position and found that it gives off correct data when moved (park, drive, etc) but the car itself does not shift
the car has 20K KM milage on it thats what i havent replaced the ISM itself as i believe its unlikely for such problem to be caused by the ISM itself
has anyone ran into a similar problem and found a solution?
thanks everyone in advance
Read codes and report them here.
MBWorld Fanatic!
Joined: May 2021
Posts: 2,524
Likes: 2,041
From: US
2008 E350, 2012 ML350, 2014 E350, 2015 ML350
i have a w166 mercedes body where the ISM stops working about 15 mins after starting the car
when first started the car shifts normally between gears but about 15 mins in the shifter stops working
i have ran a few diagnostics and found communication errors with the ISM module, so the first thing i did was check the CAN buses under the passenenger floor for any water damage, i did not find any and all CAN buses seem normal
i have replaced the steering column module and that proved of no use, at the same time i entered the datastream for the DIRECT level position and found that it gives off correct data when moved (park, drive, etc) but the car itself does not shift
the car has 20K KM milage on it thats what i havent replaced the ISM itself as i believe its unlikely for such problem to be caused by the ISM itself
has anyone ran into a similar problem and found a solution?
thanks everyone in advance
when first started the car shifts normally between gears but about 15 mins in the shifter stops working
i have ran a few diagnostics and found communication errors with the ISM module, so the first thing i did was check the CAN buses under the passenenger floor for any water damage, i did not find any and all CAN buses seem normal
i have replaced the steering column module and that proved of no use, at the same time i entered the datastream for the DIRECT level position and found that it gives off correct data when moved (park, drive, etc) but the car itself does not shift
the car has 20K KM milage on it thats what i havent replaced the ISM itself as i believe its unlikely for such problem to be caused by the ISM itself
has anyone ran into a similar problem and found a solution?
thanks everyone in advance
Out Of Control!!
Joined: Apr 2019
Posts: 11,924
Likes: 6,776
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
ISM 15MN DISRUPTION
What's interesting is OP has done a fair amount of troubleshooting to figure ISM becomes flaky 15mn after starting.
This is aiming towards poor communications... something's overwhelming CGW to disrupt SCM to ISM timely data delivery.
Indeed marginal voltage is made involved with unstable CAN networking - Display ALT Chassis voltage while driving stays above 12.6V Min and never below 12.3V while driving.
Low battery charge deliver marginal voltage during cranking to affect the whole platform - A well charged battery up goes a long way to help these vehicles run well. Stable ignition park timing depends on stable voltage.
Seasoned old drained batteries are contributing factors.
ISM uses a connector that's mounted fairly low... avoid driving through standing water when possible.
++++ VOLTAGE SENSITIVITY QUEST....
I have been wondering what precisely Mercedes uses to make this platform thrive for stable 14Volts.
Experiment with: Reboot + Float "AGM mode" to enjoy temporary transformation.
Chassis is BATTERY VOLTAGE sensitive besides ALT-LIN being a flat 14Volts.
Perhaps battery charge helps knock down voltage riples from PWM that affect COM's ?
Mercedes engineering teams are very crafty...
This is aiming towards poor communications... something's overwhelming CGW to disrupt SCM to ISM timely data delivery.
Indeed marginal voltage is made involved with unstable CAN networking - Display ALT Chassis voltage while driving stays above 12.6V Min and never below 12.3V while driving.
Low battery charge deliver marginal voltage during cranking to affect the whole platform - A well charged battery up goes a long way to help these vehicles run well. Stable ignition park timing depends on stable voltage.
Seasoned old drained batteries are contributing factors.
ISM uses a connector that's mounted fairly low... avoid driving through standing water when possible.
++++ VOLTAGE SENSITIVITY QUEST....
I have been wondering what precisely Mercedes uses to make this platform thrive for stable 14Volts.
Experiment with: Reboot + Float "AGM mode" to enjoy temporary transformation.
Chassis is BATTERY VOLTAGE sensitive besides ALT-LIN being a flat 14Volts.
Perhaps battery charge helps knock down voltage riples from PWM that affect COM's ?
Mercedes engineering teams are very crafty...
Last edited by CaliBenzDriver; Jan 23, 2026 at 04:59 PM.
Member
Joined: Jun 2025
Posts: 163
Likes: 57
From: Australia
2014 ML63, 2018 GLC43, 1929 DB victory six sports roadster
I found when my battery was getting weak problems would start 10 to 15 minutes into the drive. The engine would start perfectly but it would not run the car. I would start with the main and auxiliary battery also. A dead auxiliary battery will give trouble with shifter.
Out Of Control!!
Joined: Apr 2019
Posts: 11,924
Likes: 6,776
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
I found when my battery was getting weak problems would start 10 to 15 minutes into the drive. The engine would start perfectly but it would not run the car. I would start with the main and auxiliary battery also. A dead auxiliary battery will give trouble with shifter.
low battery voltage create more troubles.
The opposite is also true :
Stable battery voltage guarantee less troubles.
