[V8] ECU Lesson

[Coleman, David]

OK.  Anyone who actually knows what they're doing can stop reading now.

I've been diagnosing a running condition that has best been described as 'haywire'.  The symptoms are not consistent and I couldn't access the ECU codes.  But that changed last night, sort of.    We got a two different codes, MAF if key on, Idle Valve if running.  That was odd in itself, but the LED for the codes was still acting up.  With the ECU unplugged, and every single fuse and relay removed, the LED still glowed dimly.  We checked every single wire connection in front of the firewall but couldn't get the light to go completely.  But then we heard a faint click under the dash when the #4 fuse was reinserted...

I don't know how I got along for almost 3 years with this car without realizing the ECU and the ECM are not the same thing.  The ECM is under the dash, the ECU is under the rear seat.    Reading the manual I always wondered why they called it an ECU in one step, but an ECM in another.  I also wondered why the pictured ECM had three rows of terminals but mine only had two (and was un-numbered).  And lastly I wondered why the thing that supposedly had an IA chip showed no signs of tampering.

So after the mixed feelings of seeing "Motronic" staring back at me, I pulled its plug and noticed it had been soaking wet.  Still had drops of water on it, and pulling the module out revealed a nasty bit of water damage to the thing itself.  And the ECU code light was now out.

SO.  Does anyone know if the 5-speed ECM is different than that for an auto car?  And has anyone had a water leak problem around there?  Is anyone even speaking to a dolt like me?

Educated,
-DaveC.