MACS Monthly Newsletter - 2021 - MAY4

Figure 6: 2017 Chevy Volt A/C Compressor Module Operating System Software: This screen capture from GM's CAL ID website for a 2017
Chevy Volt shows the OS (operating system) section of the A/C compressor control module as NOT having an update. An update would
show a newer part number just below the OEM programmed part number, along with a note under the " Description " column giving
some kind of reason for the update.
tis2web (just Google GM CAL ID) where you can enter your customer's VIN,
select the applicable module, and see what the latest software calibration
update P/Ns (part numbers) are, along with notations on " why " the calibration was updated. Prior to using this handy website, you simply use your
scan tool to go into " Module ID " to obtain the level (part numbers) of the
current software in that module. There can be several part numbers of the
" sections " of software that comprise the overall calibration.

tains that exact P/N of software. GM used to allow that process to occur. I
can recall repairing more than a few mysterious electronic symptoms doing this procedure. The pathing of steps throughout the process of doing a
flash of software P/N " 12345 " into a module that already had software P/N
" 12345 " simply required you to check a box stating that you understood
that GM did not recommend this procedure and you were electing to do it
anyways. General Motors feels the potential risks (and warranty costs) associated with unwarranted module flashing outweighs the rare cases where
the programming of modules with the exact same software saves the day.
Even though the computer industry in general is rampant with cases where
we have to remove and reinstall software in our PCs and smart phones to
reprogram corrupted software, most automotive electronic modules don't
allow it.

Comparing what we saw in the perfect example of a calibration update
candidate in Figure 5 on the HVAC control module, the Electric A/C Compressor Control Module shows only one part number for both its operating
systems and system calibration. I sampled over twelve different 2017-2018
Chevy Volt and Cadillac CT6 PHEV VINs, and NONE of them listed a software update for the Electric A/C Compressor Control Module as the TSB
describes. Since GM no longer allows for reprogramming with the same
exact software currently in their modules, what do you do in a case like this
where the TSB tells you to do something that you can't possibly do? The
most logical assumption is to use a VCI number (Figure 8).

Getting back to our Chevy Volt / CT6 PHEV electric compressor control
module re-flash TSB, you can clearly see there are NO software updates listed
in the example screen captures shown. See Figures 6 and 7.

GM provides a very easy to use website https://tis2web.service.gm.com/

Figure 7: 2017 Chevy Volt A/C Compressor Module System Calibration Software: Just as with the previous screen capture from the
same Chevy Volt VIN, this screen capture from GM's CAL ID website shows the System Calibration section of the A/C
compressor control module as NOT having an update. An update would show a newer part number just below the OEM
programmed part number along with a note under the " Description " column giving some kind of reason for the update.

May 2021

MACS Service Reports

https://tis2web.service.gm.com/

MACS Monthly Newsletter - 2021

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