Strange recurring CEL light on 997 turbo
Discussion
Hi, I've been getting an irritating recurrent CEL in my 997 turbo over the past while. It can be quickly cleared and doesn't return for a week or so. Basically out of the blue I get the usual check engine message and light. Car behaviour does not alter at all - with or without the error message. It remains until cleared with my code reader. I just want to get rid of the irritation and clear it for good.
I've used a generic code reader to clear it and it clears fine but returns in a week or two. The code varies slightly from occurrence to occurrence but the common theme is Throttle/pedal position sensor/switch B circuit range/performance problem. Often the potentiometer is mentioned.
Today it was the following codes although it can vary slightly but always with a throttle position sensor component. Codes cleared today were:-
P0221 - "Throttle/pedal position sensor/switch B circuit range/performance problem" This is a familiar one but often I get a differently numbered but similar code which refers to the potentiometer in conjunction with the throttle/pedal sensor.
B0821 - no description in database I don't know what it is with Porsche This is not a regular message for me.
B1000 - no description in database - this is there sometimes but I don't think its always there. Looks like a general ECU message to me.
In the past month or two I have tried replacing the throttle pedal unit with another one as I believe (but can be corrected!) that the 997 throttle pedal has the potentiometer built into it. Is this correct or is the potentiometer housed separately from the pedal? The problem recurred again a week or so later so its not the pedal unit itself.
I then turned my attention to the engine end. I removed and cleaned the throttle body and also carefully cleaned the electronic sensor unit attached to it with isopropol alcohol. The images for this component are in the 996 thread I've linked below - there are images in the post about 2/3 way down the page by gk996t.
I reassembled and the car went fine until yet again up comes the latest message a couple of weeks later. I think I've done as much as I can but can anyone suggest any other things to check out? Is there another potentiometer I've missed?
All advice welcome!
Link to images below:
http://911uk.com/viewtopic.php?p=680893&highli...
I've used a generic code reader to clear it and it clears fine but returns in a week or two. The code varies slightly from occurrence to occurrence but the common theme is Throttle/pedal position sensor/switch B circuit range/performance problem. Often the potentiometer is mentioned.
Today it was the following codes although it can vary slightly but always with a throttle position sensor component. Codes cleared today were:-
P0221 - "Throttle/pedal position sensor/switch B circuit range/performance problem" This is a familiar one but often I get a differently numbered but similar code which refers to the potentiometer in conjunction with the throttle/pedal sensor.
B0821 - no description in database I don't know what it is with Porsche This is not a regular message for me.
B1000 - no description in database - this is there sometimes but I don't think its always there. Looks like a general ECU message to me.
In the past month or two I have tried replacing the throttle pedal unit with another one as I believe (but can be corrected!) that the 997 throttle pedal has the potentiometer built into it. Is this correct or is the potentiometer housed separately from the pedal? The problem recurred again a week or so later so its not the pedal unit itself.
I then turned my attention to the engine end. I removed and cleaned the throttle body and also carefully cleaned the electronic sensor unit attached to it with isopropol alcohol. The images for this component are in the 996 thread I've linked below - there are images in the post about 2/3 way down the page by gk996t.
I reassembled and the car went fine until yet again up comes the latest message a couple of weeks later. I think I've done as much as I can but can anyone suggest any other things to check out? Is there another potentiometer I've missed?
All advice welcome!
Link to images below:
http://911uk.com/viewtopic.php?p=680893&highli...
Maybe a bit of a long shot but at my garage we've had similar problems ( not on Porsche ) which has turned out to be a faulty brake light switch.
There is also a procedure for resetting the throttle body, can't quite remember what it is but it's fairly simple, like turning on the ignition for couple of minutes without touching the throttle.
Try Google for the exact procedure.
Too often fault codes give the result of a problem but not the true cause!
If I think of anything else I'll give you a shout.
Good luck
Dave
There is also a procedure for resetting the throttle body, can't quite remember what it is but it's fairly simple, like turning on the ignition for couple of minutes without touching the throttle.
Try Google for the exact procedure.
Too often fault codes give the result of a problem but not the true cause!
If I think of anything else I'll give you a shout.
Good luck
Dave
Did it happen after the exhaust and cats?
Different car but I fitted manifolds and 100 cell cats and it logged a CEL (after 3 hours) but the performance seemed unaltered. It was 'cat efficiency'. A pair of rear lambda spacers seems to have done the trick. On my previous car I had the same manifolds but standard cats and no CEL.
Different car but I fitted manifolds and 100 cell cats and it logged a CEL (after 3 hours) but the performance seemed unaltered. It was 'cat efficiency'. A pair of rear lambda spacers seems to have done the trick. On my previous car I had the same manifolds but standard cats and no CEL.
Yes, no sign of it before the change of exhaust. Im not sure how throttle position sensors would seem to be the symptoms though.
The recurrence happens more quickly now, perhaps 100-200 miles on average between resets when it would have been quite a bit longer after the installation.
No change in behaviour though with or without the Cel being on. Just fed up looking at yellow and red lights on the dash and also don't want to mask something more serious should that ever happen.
Funnily enough my OPC reset the first couple for me without charge and mentioned another car that had need lambda spacers fitted.
The recurrence happens more quickly now, perhaps 100-200 miles on average between resets when it would have been quite a bit longer after the installation.
No change in behaviour though with or without the Cel being on. Just fed up looking at yellow and red lights on the dash and also don't want to mask something more serious should that ever happen.
Funnily enough my OPC reset the first couple for me without charge and mentioned another car that had need lambda spacers fitted.
Thanks Carl. Very interesting. Im suspecting this is the cause of my (minor) woes.
Can anyone say how many o2 spacers would be needed and which sensors need spaced? A quick google on this from a US site suggests that its not all the sensors that need spaced just those past the cats. Reason is due to the difficulty in removing the sensors. The guys who fitted the exhaust had a hell of job shifting the originals and the fewer that need done the better.
Thanks to everyone for the assistance.
Can anyone say how many o2 spacers would be needed and which sensors need spaced? A quick google on this from a US site suggests that its not all the sensors that need spaced just those past the cats. Reason is due to the difficulty in removing the sensors. The guys who fitted the exhaust had a hell of job shifting the originals and the fewer that need done the better.
Thanks to everyone for the assistance.
edc said:
I took a quick look under the car yesterday (may get a chance to get the bumper off over the weekend for a better look. It seems a fairly tight fit for a straight spacer as the existing unit doesn't have much clearance. Perhaps a 90 degree spacer/adaptor?
Anyone tried removing the post-cat o2 sensors in situ?
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