MACS Monthly Newsletter - 2017 - JUL7

Another cause of logic lock up is a corrupted data
bus message. Typically in this scenario, there is another
module creating havoc on the shared CAN or other serial
bus with excessive and unintelligible messages on the
bus. This often results in U-code DTCs in good modules
pointing to a failure to communicate with a particular
module on the bus. If the bus is wired in the star (splice
pack) configuration and you are fortunate to own one of
those micro amp clamps (the $700 versions) you will find
the branch of the serial bus that leads to the offending
'blubbering idiot' module is drawing slightly more current (in micro amps - not milliamps) compared to other
modules. While this is not a 100 percent test, some techs
are having good success on the rare occasion their customer's vehicle exhibits software logic symptoms. In lieu
of an expensive 'micro' amp clamp the less than speedy
diagnostic method is to simply disconnect electronic
modules one at a time and then observing if the condition has ceased. ■

4. Nothing Worked. What Now?
a. While it's rare, sometimes the emitting
component is not faulty and the wiring has no
apparent voltage drops, ground loops and other issues that can cause a component to be an
excessive emitter. In this case, the steps listed
above in items 3a. - 3g. can be applied to the
victim device that is susceptible to EMI / RFI
rather than the emitter of interference. In other
words, begin applying the fixes of grounding,
shield, etc. to the electronic module on the vehicle that suffers from interference as opposed
to the module that appears to be causing the
interference. Sometimes a flaw in a circuit
board, poor ground or other issue can create a
condition where a module is more susceptible
to interference than it should be. This applies
more often to audio system components but
can occasionally apply to other modules such
as HVAC and powertrain.

SOFTWARE FIXES
had. GM, Ford and Chrysler allow you to program
a module with the same software it currently has.
On the surface, that sounds like a waste of time.
Many OEM service engineers will agree with that
which is why certain other OEMs not mentioned

Delphi / BSE scan capture - Dave Hobbs

Calibration chart - Courtesy Motorcraft

Sometimes software logic lock ups or other phantom software anomalies are repaired with either
new and improved software in updates / TSBs or
by simply reprograming a module with the same
software calibration (Fig. 7A and 7B) it originally

Figure 7A and 7B: On left - scan tool in Global OBD II Mode $09 or enhanced powertrain data / module info. Compare to Ford website calibration look
up table (free access via motorcraftservice.com) shown on right. If the calibration p/n is not listed on Ford's chart of latest calibrations, your software is
eligible for updating. Note: Compare Global OBD II's Mode $09 p/n to the one in enhanced powertrain module info. Sometimes the Mode $09 p/n is
listed in hexadecimal form instead of a base 10 number on some vehicles / scan tools. The two prime rules for programming are: 1. Unless the vehicle has
a problem matching the TSB / software documentation listed symptoms being addressed by the calibration do NOT flash it. In other words, if it's not
broke - don't flash it! 2. If all else fails (i.e. you suspect corrupted software) flash it!

July 2017

MACS Service Reports

http://www.motorcraftservice.com

Table of Contents for the Digital Edition of MACS Monthly Newsletter - 2017