1994 960 3ltr reoccuring 3-1-4 OBD code with lambda light

[father ted]

Has anyone out there experienced clearing a 3-1-4 code and lambda light and have it return after a couple of days.
There are lots of references to the 3-1-4 code on this forum and we are told it is pertaining to the cam sensor. My particular problem is after clearing the code in the prescribed manner it returns a few days later along with the lambda light which i assume is the "check engine" light on this model.
I have removed the cam sensor cleaned and checked the wiring and plug socket replaced and all is well for a short while until the same things happen again. If the cam sensor is faulty why does it work fine one day and not the next.
It has to be said that the car runs fine whether the light is on or off and seems to be triggered by a slight engine miss-fire. I have renewed plugs and coil packs in an attempt to sort it but to no avail. Any advice would be appreciated. Desperate almost in tears.

[93Regina]

It has to be said that the car runs fine whether the light is on or off...

Excellent...place duct-tape over Cel light, and keep on driving.

It has been said that "Generally, when cam sensors go, the car is hard to start, and revs sluggishly, since the ECM can't see cam timing," but I have no idea if this is true/false.

The sensor is hall effect type, only way to test this sensor's output signal is via oscilloscope, and it should be a square waveform.

PS: If it ain't broke, don't fix it.

[father ted]

Thanks for your input my friend. I take onboard your "if it ain't broke" advice but if a warning lamp lights and the car is fine then something is obviously amiss whether 'tis the lamp or the componant relating to the lamp.
I was frankly dissapointed at your remedy of duct-tape over the lamp and ploughing on regardless as it seemed akin to putting a band-aid on your arse and pretending you don't have haemorrhoids. I will get it right sooner or later as i am that sort of fellah who cannot sleep if there is something wrong with my beloved 960. Thanks again and please ignore my attempts at sarcasm.

[93Regina]

something is obviously amiss

I did not design the engine's computer system, so it's hard to pin the tail on the donkey.

Assuming this is a true error code, then this would suggest missing square wave pulses are afoot. But, apparently, it might be intermittent. Without a recording oscilloscope, all one could do is look at that sensor's wiring to see if it "flys about with incoming wind," and/or replace sensor components.

If sensor's wire is flexed too many times, it can/will break internally. Hall sensors can fail with time.

[father ted]

Thanks, seems i need to dig a little deeper.

[93Regina]

seems i need to dig a little deeper.

It seems to be an issue, but one might take a peek in this thread here:

1997 S90 (960) Will not start with Camshaft Position Sensor
by RickHaleParker

It seems the future Do It Yourself-er may need a recording oscilloscope, unless one has a fistful of spare parts available.

[father ted]

Some interesting posts in that forum with regard to cam sensors so thanks for that.
I got to thinking after reading that forum am i reading this right. The obd code i get is definatly 3-1-4 which in the list of codes for the 960 pertains to the cam sensor as you know. However the owners manual says that the lambda lamp when lit pertains to a fault in the fuel/ignition systems indicating that the engine do's not fulfil emission control requirements so i am asking myself why the lambda lamp should light along with the 3-1-4 code. Am i getting an eronious code? The only time i have experienced a lambda warning before with this car was about two years ago when the oxygen sensor fried itself. After renewing the same the lambda lamp went off and all was well. Its a real puzzle.