MACS Monthly Newsletter - 2021 - MAY3

the power feeds to the module during programming can be as detrimental to a successful programming operation as low voltage. GM says if you
don't have a clean power source such as a battery charger / maintainer
designed for flashing (Figure 4) to at least use a fully charged boost box
(disconnected from wall receptacle power charger) whenever flashing a
module.

Midtronics

Module Programming " 2nd Commandment " . . . Only Flash if Necessary
The 2nd Commandment in module programming is to not program unless there is a need (usually a TSB as in the case of the Chevy Volt / Cadillac
CT6 PHEV) or symptom related to a note in the OEM's calibration file website. There are risks involved in programming modules. You can have data
corruption occur during the programming process and end up either with
a module that requires some very time-consuming efforts by an advanced
mobile tech (or dealer tech) or simply " brick " the module (meaning it's now
defective).
Figure 4: Clean Battery Charger / Maintainer: Only use a battery charger / maintainer that is designed for charging
the vehicle's 12-volt battery during programming, such as
this Midtronics MSP-070-3 70-Amp clean power supply
designed specifically for ECU re-flashes. The unit allows
for manual selection of multiple voltage settings: 13.2, 13.6,
14.4 and is safe for lead-acid (flooded), AGM, Gel and EFB
(enhanced flooded battery). An update for Li-ion batteries is planned for the future of this truly smart (and clean)
battery charger.

On one of the vehicles applicable for this TSB, the HVAC module did have
a lengthy list of software updates to address some HVAC performance issues (Figure 5). HOWEVER, the TSB did NOT advise techs working on the
Volt / CT6 PHEV's corrupted A/C compressor control module's software to
program new software into the HVAC control module. The TSB instructed
technicians to reprogram the Electric A/C Compressor Control Module. Updated software for the HVAC control module might help some additional
complaints on temperature issues down the road, but it won't help the
problem of the MIL nor the U-Code and the failure of the Electric A/C Compressor Control Module to Communicate with the rest of the vehicle and
your scan tool whenever the next voltage spike occurs.

We all should know that low voltage is anything below a fully charged
battery level. Going back to dc starting and charging system fundamentals,
we know that a 12-volt battery is not fully charged at 12-volts (Figure 2).
While the battery charger in your shop may be handy and fast, you must
ensure it won't emit a noisy signal (Figure 3) into the vehicle. Noise on

Module Programming " 3rd Commandment " . . . If All Else Fails - Flash!
The 3rd Commandment of Module Programming is, " If everything else
fails, flash! " However, this does NOT apply if the OEM won't allow you to
flash the same software calibration P/N into a module that already con-

Figure 5: 2017 Chevy Volt HVAC Control Module Airflow Software Update: This screen capture from GM's CAL ID website shows the
airflow section of the HVAC control module as having several updates. Early builds would use P/N 84019128, while the latest P/N to correct " various HVAC performance improvements " would be 84197073. The actual TIS2Web calibration website
only allows you to program the module with the latest P/N. NOTE: If there are two P/Ns at the bottom of the list directly
underneath one another (instead of staggered diagonally as shown), always click your mouse on each option. When you
do so, a note will pop up on the website indicating an equipment option (i.e., automatic HVAC vs. manual). Make sure you
know EXACTLY which option your customer's vehicle has BEFORE selecting the applicable option in order to download /
program the correct software into the module.

May 2021

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MACS Monthly Newsletter - 2021

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