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ECU fault code

G

grumpy dad

Member
Joined
Dec 29, 2015
Hi
I am in England

I just got a 1993 940 2.3 turbo

it has a fault code 1-2-3 coolant temperature sensor signal missing or faulty
so I have replaced both the ECU one at the back of the head
and the temp gauge one at the front
still got the same fault any ideas

Thanks
 
Hi
just a quick up date
car was hard to start this morning
and when it started the rev counter did not work for about 30 seconds
the management light came on and the rev counter started working
switched off and then the car restarted just fine
 
That. And check how crank sensor output looks like...

But firstly go over all the grounding points with sandpaper and electric grease, bas grounds will throw ECU into really erratic behaviour.
 
Hi
I have run a ground from the battery to a stud on the thermostat housing
and cleaned the 2 on the back of the head still the same
 
nordmaschine said:
That. And check how crank sensor output looks like...
Click to expand...

How?



grumpy dad said:
yes all good so have changed both ecu and now all good

Thanks
Click to expand...

Just a guess, but did you see any oxidation on the ECU connectors? There is a chance there was just some oxidation on the pins and breaking em free and replugging them fixed it. Especially in a UK environment. I would keep those old ECU's around.....

Proper testing would include doing resistance/voltage tests at the ECU plug by backprobing, not front probing. A member here pointed out Voltage test is even better because it includes a measurement that incorporates the connection from plug to ECU. If there was any resistance there it would skew the voltage.
 
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