why say that is false, its not, the PCM does tests, and if they fail
they are truth, for sure. only why it fails matters.
some fails are indirect
why replace the most expensive part first? odd that.
why not find true cause.?
the key to understanding EFI and PCMs. is to know
how they work, its just a computer , if the inputs lie the PCM messes up. if the actuator is bad, the PCM has no control of it. its bad.
the 508 code dont mean to change a part, the PCM is not human.
we do the test detailed in the FSM to find true cause.
then replace that.
so the fsm says
Idle Air Control Motor Sense Circuit Low Input
and
The PCM detected the IAC Motor Sense circuit current was less than 175mA during the CCM test period.
Possible Causes:
- IAC motor driver circuit is open or shorted to ground
- IAC motor sense circuit is open or shorted to ground
- IAC motor is damaged or it has failed
- PCM has failed (note its last and is 1% changes here. or none.
in simple terms,
THe PCM can not control idle, you will see that. easy, driving car.
The PCM controls this AIR valve at all times, controlling idle RPM
by adding or stubtracting AIR.
The PCM has the MONITOR (like a NANNY) that monitors the IAC at all times, (at the same time as it uses it)
its a test. it see the ISC motor current is wrong.
the IAC seems to have and OPEN COIL inside, or the connector fell off ,is corroded or the wires to it snapped.
a technician checks the IAC, carefully the FSM shows all the steps
here even to the point of measuring the coil. and other checks.
that is how it is done.
most shops gander at it and just replace it, then when it fails again, a new pCM then when it fails again, oh crud, some bloke, wired in a
stinking auto remote start to this IAC and cut the power feed to it.
$1000 later , a 10cent fix. in 1minute flat.
guessing can be expensive
