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  1. #1
    sean_s3's Avatar
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    EGT Sensor again.

    It would appear that my long run of trouble free motoring in over. I had a full service carried out on the car last week and out of curiosity I did some code reading at the weekend to find that the EGT sensor fault is showing again.


    17868 Exhaust gas temp sensor 1 (G235) Implausible signal . P1455 - 35 - 10 Intermittent.



    I had this sensor replacing less that 2 years ago , can these things fail so quickly ?? Or could it be possible that something else is causing it to fail ?? This fault is the only one registered on the ecu so it doesnt look like its a knock on effect of another problem somewhere else.

    Any thought would be appreciated.

    Cheers.
    Sean.
    S3 Big Turbo

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  3. #2
    <tuffty/>'s Avatar
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    Wiring fault? I would be tempted to rewire back to the ECU tbh... I had an intermittent knock sensor issue that disappeared when I re wired it directly to the ECU... worth a punt else you could be replacing 180 quids worth of sensor for nowt...

    <tuffty/>
    Silver 2001 AMK S3. Silver alcantara interior... now with added powarrrrrrrr, torques. VAGCOM + KII-USB. >> My build thread...

  4. #3
    "Stick a V8 in it!"

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    Given its "implausible signal" rather than a circuit fault, it could be caused by a failing MAF or dodgy lambda sensor.

    The engine ECU calculates a "virtual" EGT as well as taking a measurement from the probe, and if they differ too much the ECU will flag the above code.

    IE engine runs lean due to faulty sensor, lean-ness causes high EGT, ECU doesnt expect high EGT because load isnt high enough, pops fault code.

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  5. #4
    sean_s3's Avatar
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    Thanks for the replies.

    @ Tuffty I dont know if I would be comfortable wiring it up to the ECU but I will take a look at the connection to make sure its actually in right, It may be that it has been knocked while it was in for servicing last week.

    @ Aragorn I did consider the MAF but that is a relatively new unit as well , probably around 2 1/2 years old. i think the lambda is the original. Would unplugging the MAF help in checking out this theory ?

    For the moment in time I have cleared the fault and when driven steady it doesnt come back , although 2 of the readiness tests still show as failed.

    Many thanks.
    Sean.
    S3 Big Turbo

  6. #5
    "Stick a V8 in it!"

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    which readiness tests have failed?

    Unplugging the MAF will just put the car into limp mode, so wont tell you much at all.

    Maybe check the fuel trims in block 32, if they're far out it could help narrow it down to the lambda?

    2000 A4 1.8T Sport Quattro Avant, Berry Pearl
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  7. #6
    sean_s3's Avatar
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    The test for emissions and the catalytic converter had failed but they have passed since they were orinially reset at the weekend.
    Steady driving is doing the trick as the fault has not come back but I know once on full boost it will reappear.

    I dont have the full version on vagcom unfortunatly so any further logging would have to be carried out by my local independant in order to get to the bottom of the problem.

    Many thanks.
    Sean.
    S3 Big Turbo

  8. #7
    sean_s3's Avatar
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    Right I now have a registered version of VCDS lite so I am able to tap in to more measuring blocks. What blocks would be worth checking and under what conditions ?? While idling block 118 for the egt was pretty healthy around the 330 c mark which seems reasonable.

    Im not convinced the sensor is bad, looking on other forums such as the TT forum and seat cupra forum there are several posts mentioning other problems causing the fault such as poor earth, MAF , strangled TIP etc. Hopefully we can narrow it down to a few possible factors before I spend £200 again getting the sensor replaced.

    Cheers.
    Sean.
    S3 Big Turbo

  9. #8
    sean_s3's Avatar
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    I have done some logs tonight logging blocks 001, 031 and 015 , and then another log on blocks 002 , 112 and 115 .
    Please take a look and see what you think .

    Here is blocks 001 and 031


    Group A: '001 Group B: '031
    RPM Temperature Lambda Bin. Bits Lambda Factor Lambda Factor
    TIME TIME
    Marker STAMP /min °C % STAMP
    764.8 2160 69 -2.3 1101000 765.32 0.992 0.992
    766.12 2240 69 0.8 1101000 766.61 1.008 0.992
    767.43 2120 69 2.3 1110100 767.91 1.367 0.984
    768.72 3480 69 0 1100000 769.14 1.016 0.992
    770.03 3800 69 -8.6 1101000 770.43 0.984 0.961
    771.25 4240 69 -1.6 1101000 771.75 0.945 0.953
    772.66 4680 69 -2.3 1101000 773.15 0.961 0.953
    773.95 5040 69 0 1101000 774.35 0.961 0.953
    775.26 5200 69 -0.8 1110100 775.66 0.836 0.961
    776.67 3280 69 0 1110000 777.07 1.991 1.047
    777.98 2840 69 0 1110000 778.38 1.991 1.047
    779.39 2400 69 0 1110100 779.79 1.991 1.047
    780.69 2040 70 0 1110100 781.09 1.991 1.047
    781.9 1680 70 0 1110110 782.3 1.991 1.047
    783.31 1080 70 0 1110110 783.71 1.991 0.945
    784.51 1720 70 0 1100110 784.93 0.984 0.945





    Here is blocks 002 , 115 and 112


    Group A: '002 Group B: '115 Group C: '112
    RPM Load Inj. On Time Mass Flow RPM Load Absolute Pres. Absolute Pres. Temperature Load
    TIME TIME TIME
    STAMP /min % ms g/s STAMP /min % mbar mbar STAMP °C %
    927.48 2040 14.3 1.7 5.58 926.56 1280 15 1000 1000 926.98 625 0
    928.79 2080 30.1 3.4 13.86 927.99 2080 14.3 1000 1000 928.39 640 0
    930.19 2160 54.1 5.1 23.14 929.28 2120 51.1 1000 1010 929.68 665 0
    931.49 2320 56.4 5.44 25.53 930.69 2200 55.6 1000 1070 931.09 690 0
    932.8 2720 134.6 12.58 76.64 932 2440 93.2 1770 1150 932.4 715 0
    934.21 3600 191.7 19.04 132.33 933.22 2920 166.2 2510 1930 933.71 750 0
    935.62 4440 191.7 17.68 163.86 934.62 3840 191.7 2520 2390 935.12 825 0
    936.93 5120 182.7 17.68 178.22 936.03 4640 191.7 2420 2250 936.43 900 0
    938.24 5760 172.2 22.1 188.67 937.44 5400 178.2 2290 2090 937.84 955 22.4
    939.55 6280 159.4 21.42 187.14 938.74 6000 170.7 2190 1990 939.13 1110 40
    940.85 4920 180.5 25.16 191 940.05 6160 65.4 1000 1790 940.45 1110 40
    942.06 5040 125.6 17 95.08 941.25 5040 185.7 2310 2260 941.66 1110 29.8
    943.37 4120 163.9 23.46 145.5 942.56 4320 12 1000 1210 942.96 1110 25.1
    944.78 3360 59.4 8.16 36.81 943.87 3720 12 1000 1360 944.37 1110 20.4
    946.19 3240 12.8 0 6.94 945.18 3360 14.3 1000 1190 945.68 1110 20.4
    947.6 3160 12.8 0 7.83 946.67 3200 12.8 1000 1040 947.08 1110 19.6
    949 3040 12.8 0 7.78 948.09 3120 12.8 1000 1030 948.49 1110 18.8
    950.3 2960 34.6 4.42 20.06 949.5 3000 12.8 1000 1030 949.9 1110 18




    EGT 's went through the roof and at 955 c the readings bombed out completly.
    MAF reading look pretty weak peaking at 187 g/s @ 6280 rpm. I'm certain i've had just above 200 g/s on occasion.
    How does block 031 look ?

    Any thought would be greatly appreciated.
    Thanks.
    S3 Big Turbo

 

 

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