Motronic M1.5 Discussion Thread.

[Robsey]

This is where we can discuss the Motronic M1.5 fuel injection control system as used on the 1991 onwards 20SEH, C20NE and 20NE set ups.
The most common ECU Alpha code for M1.5 is "GE"

Note that this is the 55 pin ECU, not the earlier M4.1 ECU that only has about 30-odd pins.

Here is the main thread, where it explains how this particular set up works.

viewtopic.php?f=70&t=16420&p=165882#p165882

[Robsey]

I think everything should be read in context, as it is easy to jump to conclusions with comments such as -
However, fitting alternative plugs should be approached with caution as the effects may be detrimental to good running and economy being used for something as simple as the Octane Coding Plug.

Any component that is mal-adjusted, ill-fitted, poorly maintained or simply not in it's optimum condition will impair the running and economy of the engine.

[Mk3alan]

Excellent description of how it all functions and is connected, very useful.
Interesting about the knock sensors, I haven't got them fitted to my 20ne but I have never heard it pink.

Alan

[cavalier1990]

Really good description of the function and operation of the whole system. I'll need to sit down one night and read it all, as it will apply to my diplomat and my senator. Dues to you for finding and posting this Robsey

[Robsey]

Just doing my public duty.

Always happy to research and share.
Pity it still doesn't help me identify why my emissions are so high.

Even pulled the engine coolant temperature sensor, idle control valve and octane plug connectors today - one at a time.
None of them made a jot of difference to the idling economy. Totally baffled.
And I could smell the rich-ness too.

Short of stripping the head to check for sticking valves, I am at a total loss.

[cavalier1990]

Scunner these bloody emissions, worryin about mine failing again, fixed all exhaust leaks, new dizzy, air intake pipe, new filter. Is maybe your injectors leaking ie dripping fuel, what's fuel pressure like?

[Mk3alan]

Just for you Robsey! I checked my coolant sensor when cold (about 10am this morning) it measured just over 1000 ohms, checked it again during a journey, guage read 85 and sensor had dropped to 100 ohms.
I wondered if your sensor is telling ECU it's cold?

Alan

[Robsey]

I did a very crude test on my ECT sensor.
I unplugged it, and the revs lept up.
Reconnecting the sensor settled the revs back down again.

This more or less indicates to me that the sensor is working well.