ECU and code reading.
 

I am wondering if I can read codes from the ECU on my 89 300E as I was on my 300ZX. This was very helpful when I had assorted problems over the years. Also...I hate to sound dense, but where is the ECU for this auto?

Thanks!

BTW....This forum is so much more civilized than others I have attended. :)

Bill Tobin
91 Volvo Brick 740
89 300E(removed retard resistor and running 89 w/no knock)

If your car has California emissions then there is a red LED & pushbutton on the diagnostic connector next to the battery. IF not then you car doesn't have any "stored" codes that can be read. The CIS ECU is behind the plastic cover behind the battery.

As Doc pointed out there are no retained codes in memory on early federal cars. They do have real time fault codes as expressed in On -Off ratio testing. It can be read off pin #3 in the diagnostic connector on the left fender. There is a special tool but it can be read with a scope using the technique explained in the DIY article "evaluating engine controls".