# Please Help! EGT Sender 1 G235: Implausible Signal



## radical (Jun 14, 2002)

Hello Guys
I have been experiencing a progressively more frequent power-on /power-off jerking, starting at around 5200rpm/220km/hr in 6th gear with my chipped S3, which phenomenon disallows me to push through to normal higher speeds. I have changed the DV, sparkplugs, lower O2 sensor, cleaned the MAF meter and am waiting for the availability of revised coilpacks. The MAF meter cleaning seems to have resolved the fault: "Mass or Volume Air-Flow-G70 Circuit: High Input".
One fault that I require more information about is "Exhaust gas temperature sender 1: Implausible signal", if anyone would be so kind to share their knowledge/experience in this regard. The technician at my dealer says the error is inconsequential, but I disagree, based on the abstract below, which is all I could find on the net (AudiWorld).
I see one EGT sender on the rear of the turbo. Is this sender 1 -G235? Are there two (as on the S4)? Anyone experienced the same or similar symptoms / codes?
Any input appreciated, irrespective of how basic / advanced, since I am running out of possiblities to pursue.
Regards

Stuart
[email protected]
http://www.gaiaresearch.co.za/s3 
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AUDIWORLD ABSTRACTS: S4 Fora
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A) Exhaust gas temperature sender G235 and G236 
To facilitate exhaust gas temperature control, the exhaust gas temperature must be recorded to a high degree of accuracy. 
An accuracy of ± 5 °C is achieved in the measurement range from 950 °C to 1025 °C. 
The exhaust gas temperature sender is located inside the exhaust manifold upstream of the exhaust gas turbocharger. 
It comprises a measuring sensor and evaluation electronics. 
The measuring sensor and the control unit are permanently connected by means of a shielded, heat-resistant wire. 
The evaluation electronics convert the signal which the measuring sensor generates into a pulse-width-modulated signal (PWM signal). 
This is a square-wave signal with a fixed frequency and a variable pulse duty factor. The pulse duty factor is expressed as a percentage . The measurement range extends from ³10% to £90%. A specific pulse duty factor is assigned to each temperature (refer to diagram). 
Substitute function and self-diagnosis: A pulse duty factor of 99% is recognised as a fault. 
A fault is detected as of a certain enrichment quantity. If a sender fails, the charge pressure is reduced to a safe level and an emergency enrichment characteristic (engine speed-dependent) is used. 
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B) Subsystems of the Motronic 
Exhaust gas temperature control 

A new feature of Audi automobiles is a function which monitors exhaust gas temperature over the entire engine speed range. 
For turbocharged engines, the maximum permissible exhaust gas temperature is a key design criterion. 
To protect the exhaust gas turbocharger and the exhaust manifold, the exhaust gas temperature should not exceed 1000 °C for a lengthy period of time. 
Since many of the components which influence the exhaust gas temperature have tolerances, thermodynamic adaptation previously took place at 950 °C for safety's sake. 
This was achieved by enriching the air/fuel mixture. 
The exhaust gas temperature is recorded in a cylinder-bank-specific manner by the two exhaust gas temperature senders G235 and G236. 
The Motronic controls the exhaust gas temperature to 980 °C by enriching the air/fuel mixture. 
It is therefore possible to largely dispense with the prophylactic enrichment process that has been standard practice until now. 
The mixture is only enriched... 
... when necessary and 
... to the extent necessary. 
This means that engine operation with lambda = 1 is possible up to high load and engine speed ranges. 

Advantage: * Improved efficiency and reduction of fuel consumption as well as exhaust emissions. 
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C) My right side EGT sensor failed, eventually blew a turbo
When that EGT sensor failed, it put the engine in sort of a limp mode. It only made 5psi firm...as opposed to 8-9psi with the stock ecu. Definitely a good thing to possibly keep track of. You don't want these things to fail. It's bad. Especially if you have a chip, because a chip will overide the limp mode the stock ECU goes into, and run full boost on your car...when it can't keep track of EGT's. You'll get all kinds of shuddering, pinging, weird performance.
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D) Exhaust gas temperature errors or Oxygen sensor errors?
If the exhaust gas is too hot it could indicate that you engine has been running too lean. This can be caused by an intake leak after the MAF, in particular under boost when the engine is in open loop mode. During cruise an air leak is not so serious because the oxygen sensors will help keep the mixture correct. Under boost (say WOT) the ECU ignores the O2 sensors and just uses MAF, knock, temp and some other sensors. At least that's how it works in DSMs, I suspect Motronic is similar. 
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