EEC-IV Questions

[atsakiri at ford.com]

> >2)  Do Ford dealers have the capability to check an EEC-IV "on the bench" 
> >(out of the vehicle)?
> >
> >As stated above, I've tried to diagnose the vehicle using the internal 
> >diagnostics, but I get no reply.  The vehicle appears to be running in 
> >"limp home" mode, and the sensors I've checked look okay (It's pretty 
> >tight in an Escort's engine compartment)
> >

>         In reply, yes a Ford dealer can check the EEC-IV out of the car with
> a device known as a breaker box, and did you try checking the air meter( I
> think these have one.. you did'nt mention the year).  These will implement
> the limp home mode anytime.

I'm unable to go into details due to corporate policy, but I'd hate to
see you chase sensor or actuator failures as a source of your limp-home 
failure.  All of what follows is available in publicly accessible
(though not necessarily free) documentation anyway.  

Sensor or actuator failures will initiate failure mode actions
by the powertrain control module (PCM), but these actions are not the  
same as limp-home mode.  For example, when a sensor fails, the PCM may 
use the inputs from other similar or related sensors to estimate the 
value which can no longer be directly measured.  Limp-home mode is 
a response to a fault inside the PCM, like a CPU or memory failure.

I don't know of any bench testing capability at dealerships.  I'm sure
they have what are called "breakout boxes," but these merely provide easy
access to the PCM I/O signals.  The breakout box does not generate or
simulate signals produced by sensors or actuators.  The PCM is not a
dealer serviceable part (just replaceable).

One last thing, a MAF sensor failure will definitely _not_ put the PCM 
into limp-home mode. (I'm very familiar with the EEC algorithms for
the MAF sensor; This one I'm sure about.)


Anthony Tsakiris

The opinions expressed are not necessarily those of my employer.