Bad EGT(s) Log and Graph
08-12-2005, 04:06 AM
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Bad EGT(s) Log and Graph
In hopes of trying to get a better understanding of the ECU and tracking down why the ECU will not complete the Catalyst Readiness Test I performed a log. This is in relation to a previous post:
<a href="https://forums.audiworld.com/s4/msgs/2078819.phtml" target="_blank">Could P1454 Cause the Catalyst Readiness to Fail or Not Complete?</a>
BTW, thanks AW for all of the valuable input, I guess there was no wheel content or FATs times bragging, so it was overlooked </sarcasm> ;-)
Anyway, back to the topic. There is obviously something wrong with what appears to be both EGT sensors. Both read 945 for the most part for a 20 minute drive with some acceleration. One of them sometimes jumped to 1025 for a moment but then came right back to 945.
Now I doubt they are only using 4 bit A/D, more than likely at least 8 bit but most likely 12 bit, so the steps would certainly be larger than this.
What I don't get is why there is only one code set for one of the sensors when clearly both are not functioning correctly. If I clear the code one of several EGT codes comes back nearly immediately when the engine is hot. It is almost as if the ECU quits the monitoring the health of the signals once a code is set for one.
But it does appear the catalytic converter readiness test does rely upon the health of these sensors. Although this is not conclusive it does seem to be the case. I spoke to someone at the dealer and they seemed to agree. So if you have a bad EGT sensor and your ECU has been reset, you may not be able to pass an OBDII Emissions test.
Guess it is time to swap out both sensors just to be sure.
Below is a quick log of a portion of the journey. It is just a snip but the rest looks basically the same.
<img src="http://www.flwse.com/images/steve/Audi_Tech/BadEGTLog.JPG">
<a href="https://forums.audiworld.com/s4/msgs/2078819.phtml" target="_blank">Could P1454 Cause the Catalyst Readiness to Fail or Not Complete?</a>
BTW, thanks AW for all of the valuable input, I guess there was no wheel content or FATs times bragging, so it was overlooked </sarcasm> ;-)
Anyway, back to the topic. There is obviously something wrong with what appears to be both EGT sensors. Both read 945 for the most part for a 20 minute drive with some acceleration. One of them sometimes jumped to 1025 for a moment but then came right back to 945.
Now I doubt they are only using 4 bit A/D, more than likely at least 8 bit but most likely 12 bit, so the steps would certainly be larger than this.
What I don't get is why there is only one code set for one of the sensors when clearly both are not functioning correctly. If I clear the code one of several EGT codes comes back nearly immediately when the engine is hot. It is almost as if the ECU quits the monitoring the health of the signals once a code is set for one.
But it does appear the catalytic converter readiness test does rely upon the health of these sensors. Although this is not conclusive it does seem to be the case. I spoke to someone at the dealer and they seemed to agree. So if you have a bad EGT sensor and your ECU has been reset, you may not be able to pass an OBDII Emissions test.
Guess it is time to swap out both sensors just to be sure.
Below is a quick log of a portion of the journey. It is just a snip but the rest looks basically the same.
<img src="http://www.flwse.com/images/steve/Audi_Tech/BadEGTLog.JPG">
08-12-2005, 04:47 AM
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The EGT sensors never read below 945°C...
Their operating range is 945°C to 1035°C.
During most normal (and even WOT) driving, you probably won't trip the 945 threshold.
If you only have a DTC from one EGT sensor, I'd initially replace that one and then see how things are. Would suck to spend ~$200 on a sensor you don't need.
-Dave Pramanik
During most normal (and even WOT) driving, you probably won't trip the 945 threshold.
If you only have a DTC from one EGT sensor, I'd initially replace that one and then see how things are. Would suck to spend ~$200 on a sensor you don't need.
-Dave Pramanik
08-12-2005, 04:51 AM
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For some reason I had F in my head, DOH
Although it clearly shows Celcius. That does make sense then because 945 C = 1733 F which is high.
So, the ECU only responds with a narrow range using these sensors as, more or less, a high limit alarm?
So, the ECU only responds with a narrow range using these sensors as, more or less, a high limit alarm?
08-12-2005, 05:02 AM
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Ah gotcha and thanks...
So, with the one sensor sometimes jumping to 1025 and 1035 even during normal driving would more than likely be the source of the code. This would also explain some of the bucking I get once the car gets warm and the sensor starts acting up.
I wonder what type of sensor is being used, Type K TC??
I wonder what type of sensor is being used, Type K TC??
