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        General >> Give/Need advice to/from others >> Fault codes.... real or not !
        
(Message started by: Adrian on Mar 23^rd, 2006, 11:11pm)

Title: Fault codes.... real or not !
Post by Adrian on Mar 23^rd, 2006, 11:11pm

My 2.9 24v cossie usually does around 50 miles to a tenner of fuel, but recently it has only been doing 30. I checked the plugs, leads etc, the air filter, and even cleaned the MAF, but still no joy at returning 50 to a tenner. I found a mechanic who had a proper diagnostic fault code reader, and the reader said the HO2S sensors were faulty. Before changing the sensors for new, this mechanic suggested that he clear the stored fault codes, and I take the car for a drive to see if the same fault codes come up again.He explained that sometimes, little glitches can cause fault codes to register, when none really exist.I was dubious, but thought that it can't do any harm to try.I took the car out for a spin round town for about half an hour, then returned to have it checked again.I was totally amazed when no fault codes came up on the diagnostic fault code reader.The mechanic then checked the mixture with a probe in the exhaust(the type used for MOT's).The machine indicated that my car was fuelling correctly. I was baffled ! Up until now, my car was guzzling fuel at an alarming rate, but all of a sudden it seemed to be perfect. I started to wonder if the fault codes had somehow caused my car to react to them by altering the running mixture, and that now, without those codes, the car had returned to running perfectly.The only way to test, would be to put a tenner of fuel in, and see how many miles I get. The gauge was telling me I had approx. 0.4Litres of fuel, and 2 miles of driving left, prior to putting in the tenner.Lo and behold...I got just over 52 miles out of that tenner, before my gauge was telling me 2 miles left until empty. My car seems to be back to it's old self, and all that was done, was that the fault codes logged in the ECU were removed.

Title: Re: Fault codes.... real or not !
Post by Baw_Flinger on Mar 24^th, 2006, 7:47am

False fault codes will come and go, where geniune ones will stay until fixed. The codes have no effect on how the car runs, they are just logs of what the sensors are telling them so that is a strange one indeed. Have you added any fuel treatments recently? Any other signs of poor performance/noise?

Title: Re: Fault codes.... real or not !
Post by Snoopy on Mar 24^th, 2006, 8:08am

The Very cold weather does have an effect on the fueling. Also make sure the car is reaching the optimum operating temeperature. Is the thermostat working properly. Wait and see if it improves as the weather gets a bit warmer!

Title: Re: Fault codes.... real or not !
Post by martin_rowe on Mar 24^th, 2006, 8:57am

O2 sensor fault could have been logged at any time since it was last cleared, caused by air leak, misfire, wiring fault, or even a duff sensor.