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Strange Lambda Sensor Error

5K views 11 replies 5 participants last post by  alfa166ts 
#1 ·
Hi all,

I’ve recently (for the last month or two) had a problem with an MCSF failure on my car.

I’ve checked, and the error given is always P0150 – Lambda Signal 2 above Cat No Signal.
Using FiatECUScan (very good!) I’ve graphed the response of all 3 Lambda Sensors also showing Engine RPM (see below). All readings were taken with the engine at operating temp (88-90C)

As you can see, the Bank1 Pre-Cat Sensor seems to be responding normally. However the Bank2 Pre-Cat Sensor is at a constant 0.465V.

My immediate thought was “Ah, it’s a dodgy sensor, I’ll replace it”. However I did, and no difference.

So I thought “What if I swap the sensors around to see if the problem replicates?”
I did this, and get the same basic output. This indicates to me that both pre-cat Sensors are working fine.

I also checked the wiring continuity from sensor to ECU, and this appears to be fine.

Anybody got any thoughts?

To clarify, the replacement sensor is NOT an OEM sensor. However it doesn’t throw up any faults when connected on the other bank, so I don’t think it’s an incorrect resistance problem.

Also the car is a ‘01 147 1.6TS.

Thanks for any help, this is really bugging me.
 

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#3 ·
I've tried clearing the errors, it switches off the engine light for about 20 miles but then comes back on again.

The car runs pretty much fine when up to temp, but seems to be running very lean when first started (stutters, lack of power, etc).

I'm just sick of getting that stupid MCSF warning constantly. The car shouldn't do that!
 
#5 ·
Having more or less the exact same problem as you.

Refer to http://www.alfaowner.com/Forum/alfa...lem.html?highlight=interesting+lambda+problem

Also have the stuttering in the morning, although MCSF has stopped pooping(sic) up at least.
Beginning to wonder if there is damage on the ecu pcb, specifically where the pin is mounted. Not sure what else it can be, as all the obvious, and less obvious possibilities have been eliminated?
 
#9 ·
Hi all. Took out The connector plugs for the ECU to discover a whole lot of engine oil in the socket!
Obviously a previous owner had been very 'excitable' when topping the car up. It looks like it has soaked into the wiring loom and collected un the socket on top of the ECU.
I'm going to remove this as much as possible and see if
it was a bad connection problem.
Does anybody know if the ECU is fully sealed? Am I safe soaking in a load of isopropanol to clean out the socket?
Dunno how I missed this up to now.
 
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