[Shotimes] ECC Codes...

[George Fourchy]

On Mon, 29 Nov 2004 19:33:18 -0500, ROBERT SCHIRMER wrote:

>I'd love to check the connections to the PCM, but what the heck is a PCM, and where is it located? Gotta keep it simple (for my sake if no one else!)

Hey, no problem!!  I remember when I was afraid to go past taking a tire off!!

The PCM (stands for "Powertrain Control Module) is the "computer" (that's actually
what it is) that runs the engine, by generating (the coil pack actually makes the
high voltage part, but it gets signals from the PCM) and timing the spark, and
metering the fuel to the cylinders.  It is what makes modern fuel injection
possible, and got us past carburetors and very dirty exhaust.  It is physically
located (in Tauri) in front of and above the glove compartment.  It is reachable and
removable, if you want to (you don't; I'm just giving you guidance to its location),
by emptying the glove compartment and swinging it all the way down toward the floor.
 The plug is called the "60-pin connector", and is visible under the hood, at the
top of the firewall (below the rubber seal) just below the passenger side wiper
blade.  There is a black shroud about one inch by 3 inches (buried under lots of
wire looms), with one small hex head bolt in the center, which keeps the connector
plugged into the PCM.  It has read-only memory (called a MAP), which is the
programming that the engineers did when they set this car up during its design
phase; memory that can be erased, where codes are stored for telling the service man
what is wrong; and the diodes and transistors that actually do the work of sending
and receiving the signals to and from the various sensors and devices like injectors
and the coil pack.  It operates on about 5 volts DC, so that it won't get cooked
when a voltage spike comes along, or when a circuit gets grounded if a wire gets cut
or melted (happened to me!).  This is how capable it is of running the engine....at
75 MPH (3000 RPM), it triggers a spark plug (any one of the six) and checks that
cylinder's mixture once every 18 thousandths of a second......yet at that speed it
only works about 35% of the time, and can relax the rest of the time...it has that
much excess capacity.  Remember, the suggested redline of this engine is 7,000
RPM....that's a lot more than 3,000.  They almost never fail because they are so
underworked.

It has its own separate wiring (doesn't use the big cables) to get power from the
battery.  Bad connections here were what were happening to the guy's car in the
thread, and also to me a couple of years ago when I was trying to drive a new
purchase across the country.  The computer MUST have secure and stable power to do
its job, and in his case, the ground wire bolted to the fender just in the vicinity
of the power steering reservoir was loose, so the power was fluctuating.  In my
case, the idiot that had the car before had changed the battery terminal, and had
not insured the hot side of the circuit was securely fastened to it.  Cost me BIG
bucks....the car quit in Oklahoma, and I was driving it from Florida to
California....had to rent a car to come home, then go back with my Crown Vic to tow
that one home.  The fix would have been 2 bucks if I'd known what was going on.  The
clue that the computer is not powered when the key comes on is the dim CE
light....it only is getting partial voltage, rather than the full 12.

I'm SURE you will have more questions.....I love to answer them.  Ask away.

George