My lambda problem
Discussion
I'm hoping someone will help. The car went in today to have the lambda (oxygen sensor) changed. Now the exhaust light comes on and goes off but I know its the lambda sensor as it has been shown on diagnostic before.
The ECU told the technician it was the lambda sensor, so he checked it but it was giving no feed back to the ECU, now he thinks this is due to a break in the wire from the exhaust to the ECU, they also sprayed some cleaning agent on the ECU as it had some sort of fur growing on it.
My question is wouldn't a failed sensor not give a feedback anyway? How right do you think the technician is? He seemed like a nice guy and there was no charge for the whole day of investigating.
Calling on the knowledge of Dr G, Tame Technician and anyone in the know please
The ECU told the technician it was the lambda sensor, so he checked it but it was giving no feed back to the ECU, now he thinks this is due to a break in the wire from the exhaust to the ECU, they also sprayed some cleaning agent on the ECU as it had some sort of fur growing on it.
My question is wouldn't a failed sensor not give a feedback anyway? How right do you think the technician is? He seemed like a nice guy and there was no charge for the whole day of investigating.
Calling on the knowledge of Dr G, Tame Technician and anyone in the know please
Most lambda sensors when they are working swing from 0.1 volts to 1.0 volts. When they go faulty they stop swinging, so you get a flat line, but it could be 0.1 or 1.0 or even a little bit in between. If its says 0volts then its open circuit (not connected to the ECU, broken wire or similar)
However there are some lambda sensors that dont swing, call broad band sensors, these can lead you the wrong way and make you think you have 0 volts must be open circuit when its not the case.
More input required.
Who diagnosed it? and how, did they just read the fault memory?, have you rechecked the fault memory since??. Does you car car have 1 or 2 lambda sensors? was the correct one replaced if it has 2.
I think 1.6 FSI's have 1 upstream lambda and an NOx sensor behind the cat.
Is it definitely the Lambda sensor and not the NOx sensor that is at fault??.
Did they clean the actual engine management ECU (under the scuttle panel) or was is a little box under the car near the exhaust its self.
I dont do golfs, but With TT's (basically the same) often the car reports the fault code for a lambda sensor but the connectors for the lambda sensors are full of water and corroded (green/blue fur) this makes it impossible for the feed back signal to get back to the ECU and so the fault is logged.
If the car logs the code for a lambda sensor and you fit a new one, and it still logs the code, the fault is between the sensor and the ECU. Could be high resistance caused by corrosion or a broken wire.
It this seems really confusing and complicated, Welcome to my world, its not just a case of pluggin it and having it tell you whats wrong, like every body thinks it is.
However there are some lambda sensors that dont swing, call broad band sensors, these can lead you the wrong way and make you think you have 0 volts must be open circuit when its not the case.
More input required.
Who diagnosed it? and how, did they just read the fault memory?, have you rechecked the fault memory since??. Does you car car have 1 or 2 lambda sensors? was the correct one replaced if it has 2.
I think 1.6 FSI's have 1 upstream lambda and an NOx sensor behind the cat.
Is it definitely the Lambda sensor and not the NOx sensor that is at fault??.
Did they clean the actual engine management ECU (under the scuttle panel) or was is a little box under the car near the exhaust its self.
I dont do golfs, but With TT's (basically the same) often the car reports the fault code for a lambda sensor but the connectors for the lambda sensors are full of water and corroded (green/blue fur) this makes it impossible for the feed back signal to get back to the ECU and so the fault is logged.
If the car logs the code for a lambda sensor and you fit a new one, and it still logs the code, the fault is between the sensor and the ECU. Could be high resistance caused by corrosion or a broken wire.
It this seems really confusing and complicated, Welcome to my world, its not just a case of pluggin it and having it tell you whats wrong, like every body thinks it is.
It's clearly not sir and thank you for your reply.
The car was diagnosed previously by a VW tech a few months ago but he advised me to leave it until the light came on. The light has come on and off in the past few weeks so I took it to an independant VW specialist, asking them to check the ECU and change the lambda sensor. I was told there are two lambda sensors and the ECU said it was the lambda sensor but I didn't ask which one (doh!).
I don't know if they checked the fault memory but they must have because the light was not at the time I gave it. He said they cleaned the ECU terminals to see if that changed anything. They want me to take it again which I'm quite happy to do but leaving my car there the whole day is a bit of an issue. But I guess I should check the ECU again to see if the fault still exists.
When the VW tech scanned it on his fancy computer the fault was showing as intermittent. So it's possible that only the sensor has failed and there's no problem with the wiring since the sensors can give 0V readings?
The car is a 1.4 FSI 2004 Golf
The car was diagnosed previously by a VW tech a few months ago but he advised me to leave it until the light came on. The light has come on and off in the past few weeks so I took it to an independant VW specialist, asking them to check the ECU and change the lambda sensor. I was told there are two lambda sensors and the ECU said it was the lambda sensor but I didn't ask which one (doh!).
I don't know if they checked the fault memory but they must have because the light was not at the time I gave it. He said they cleaned the ECU terminals to see if that changed anything. They want me to take it again which I'm quite happy to do but leaving my car there the whole day is a bit of an issue. But I guess I should check the ECU again to see if the fault still exists.
When the VW tech scanned it on his fancy computer the fault was showing as intermittent. So it's possible that only the sensor has failed and there's no problem with the wiring since the sensors can give 0V readings?
The car is a 1.4 FSI 2004 Golf
Its probably just the sensor, but obviously you need to know which one and make sure that is the one that is change.
The specialists idea to try cleaning the connections first is valid, you should use the car for a while now and see if the light comes back on, or simply have the codes read again after a week or 2 regardless of the light. If there is no reoccurrence of the fault, then you don't need to do anything.
I have always been trained, it should be 0.1 to 1.0 volt. this is an example of one swinging.
http://www.youtube.com/watch?v=SLgdaWCuKVo&fea...
If it drops all the way to 0v then its open circuit.
Braud band sensors are different and MIGHT give a 0volt reading when everythings ok. But having never seen a 1.4FSI in my life I dont know if it had a broad band sensor or a normal (swinging) one.
The specialists idea to try cleaning the connections first is valid, you should use the car for a while now and see if the light comes back on, or simply have the codes read again after a week or 2 regardless of the light. If there is no reoccurrence of the fault, then you don't need to do anything.
I have always been trained, it should be 0.1 to 1.0 volt. this is an example of one swinging.
http://www.youtube.com/watch?v=SLgdaWCuKVo&fea...
If it drops all the way to 0v then its open circuit.
Braud band sensors are different and MIGHT give a 0volt reading when everythings ok. But having never seen a 1.4FSI in my life I dont know if it had a broad band sensor or a normal (swinging) one.
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