MACS Service Reports - 2015 - MAR3

Motorcraft Service

Free owner's manual downloads are just one valuable (yet
free) feature at Motorcraft's ESI site. If you click on OBD II
Theory & Operation, you'll be directed to a page that contains
a long list of downloadable PDF documents for Ford model
years 1996 through the current 2015 model year. These PDF
files are categorized by Gas, Hybrid and Diesel. At first glance
of the description OBD II Theory of Operation it would appear
to be mundane, but these files ranging from 100 pages to
over 400 pages are each VERY in-depth documents regarding anything you want to know about how Ford emissions
and engine management systems work. If you are tackling
a late model Ford thermostat monitor problem, for example,
this document affords some real insight.

A simple click from OEM1STOP, this Ford website
is absolutely aftermarket tech friendly with a category on the left side of their home page designated
Non-Subscription Services, giving you the ability to pull
up any Ford, Lincoln or Mercury's owner's manuals
/ owner's manual supplements should the printed
manual be missing from your customer's glove box.
We've all been in a position of trying to determine exactly how something is supposed to work before attempting to repair it. The old saying "If it's not broke
you can't fix it" still applies in the year 2015. Take
compressor operation for example. Years ago, when
you pressed "Econ" on the HVAC head it meant the
compressor would not be running - at all. Today, depending on whether the vehicle is a hybrid or not, the
Econ button may mean the compressor runs, but runs
less for fuel economy's sake. On some GM stop/start
hybrids and pre-2010 model year Ford hybrid SUVs
with mechanical compressors, Econ may mean the gas
engine shuts off at idle (to save fuel) and then starts
back up during that idle situation when the evaporator temperature sensor's value triggers the HVAC
head to request A/C compressor activation, which of
course requests a gas engine restart. On a hot day, the
gas engine may run all the time, even if the vehicle
is stopped in traffic. Knowing this can help you educate your customer when either an A/C performance
or fuel economy complaint is being discussed. Vehicle
owner's manuals, being PDF based documents, means
you can even copy and paste sections into your repair
order fields for record keeping or sharing with your
customer via e-mail.

From Motorcraft Service Website - Detailed OBD II
Thermostat Monitor Info

Figure 4: Block diagram of an engine cooling system.

Dave Hobbs

For the 2009 model year, the thermostat test has been enhanced to reduce the time it takes to identify a malfunctioning thermostat. The enhanced monitor includes a model
which infers engine coolant temperature. During a cold start,
when the thermostat should be closed, the monitor uses a
model of ECT (Engine Coolant Temperature) to determine
whether actual ECT should have crossed the (WUT) Warm
Up Temperature threshold.

NASTF

motorcraftservice.com

Once the ECT model exceeds the WUT threshold, after a calibratable time delay, measured ECT is compared
to the same WUT threshold to determine if ECT has
warmed up enough. If ECT has warmed up to at least the
WUT threshold, the thermostat is functioning properly. If
ECT is too low, the thermostat is most likely stuck open
and a code P0128 is set.

Figure 3: www.OEM1STOP.com is an easy way to find all the various OEM
ESI websites.

March 2015

Figure 5: Graph showing coolant temperature rise over time.

MACS Service Reports

http://www.motorcraftservice.com http://www.OEM1STOP.com

Table of Contents for the Digital Edition of MACS Service Reports - 2015