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S4 - Cannot test EGT using Vagcom - is it dead ?

brasiliangringo Jan 20, 2011

  1. Following a P1458 cel code, I'm using vagcom measuring blocks 112, 220, 221 (as per Bentley manual instructions) to test the EGTs. It's noted that exhaust gas temperature needs to be +945c and greater than 5000rpms for things before any values will be measurable. Well I must have done gears 1-3 to the red 3 times after the car had warmed up but still no change to the default temp value of 945c.. So am i to assume the EGTs are dead, surely exhaust gases wld be hot enough to register if they where working ?

    I also have P1113 and 1131 (O2 sensors).. need to test these but car passed MOT with flying colours.. Lambda = 1.0..

    I also did a MAF test as know this is an issue on these cars but values seem spot on according to the research i have done. Ie test 22 peak mass air flow g/s is 0.87 of full power and test 32.. -0.8% so well within the +/-10%.

    Car feels fins to be fair, perhaps just a little thirsty but runs smooth and pulls hard..
    Last edited: Jan 20, 2011
  2. Blue_Thunder

    Blue_Thunder Well-Known Member

    That is correct, your EGT's will only show +945C on Vagcom unless the EGT actually rises above that.
    I've got a failing sensor at the moment and on WOT runs at high revs, it spikes from 945C to about 1130C (I think) which is the maximum value it can read.

    So if yours is sticking at 945C, I would say it sounds like they are working ok. You might find if you do a 3rd-4th gear run up to redline then it might show up an issue.
  3. aragorn

    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

    early ECU's cant read the EGT's at all, i dont know the cutoff though.

    What is the exact fault for the lambda? It might be a heater fault, rather than the element itself, in which case they will work, but will take longer to start giving readings without a working heater.
  4. The heater ON/OFF indicator on the VAG Com measuring block test does not fluctuate quickly .. it is rather slow.. Is that normal? The test procedure simply states it should fluctuate but not how quickly..

    17539 - Oxygen (Lambda) Sensor: B2 S1: Internal Resistance too High

    P1131 - 35-10 - - - Intermittent

    17521 - Oxygen (Lambda) Sensor: B1 S1: Internal Resistance too High

    P1113 - 35-10 - - - Intermittent
  5. aragorn

    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

    Looks like two duff sensors to me :(
  6. Thanks, what the best way to test them to be sure - using a voltmeter ?
  7. murran

    murran Well-Known Member

    with those two fault codes, id replace both the 1st o2 sensors, then clear the codes, clean and reset the throttle body adaptions and then go from there.
  8. Do you think 2 bad O2 sensors could also be responsible for the EGT codes?
  9. I phoned in the problem to an independent VAG & Porsche speciaist Jim Price at Independent Garage Services in Eastleigh near Southampton and without pausing for thought, he said ''its more likely to be a leak in the vaccum system..'' Sure enough, he was absolutely right. Two new one way vales total £20 with one hours Labour and all codes have gone!! He also informed me the brake system is vacuum assisted and the leak was negatively effecting them.. they now feel much firmer.

    In a nut shell, do a Leak test if you have my symptoms HOWEVER i should also add that i developed an excessive boost code subsequent to this initial post.

    Cant recommend IGS high enough, really know their onions and prices are very competitive, half the price of main dealer..
    Last edited: Feb 23, 2011

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