Audi A6 C5 2.7t Allroad - Emissions MOT Failure - Help please

[Toy]

Hi folks,

I know this isn't the most exciting thread but..... I have an Audi Allroad 2002 2.7t which is failing on emissions. I enjoy this car so much but am risking having to scrap it because I can't get it past the MOT emissions.
Is anyone able to help my diagnose the issue or point me in the right direction? I would really appreciate your help
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First MOT Test
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Natural idle test is a pass
CO Actual value 0.415 (Max Limit 0.5) Pass

Fast Idle Test
CO Actual value 2.533 (Max Limit 0.3) Fail
HC Actual Value 121 (Max Limit 200) Pass
Lambda Actual Value 0.924 (Min 0.970 Max 1.03) Fail

Second Fast Idle Test
CO Actual value 2.522 (Max Limit 0.3) Fail
HC Actual Value 127 (Max Limit 200) Pass
Lambda Actual Value 0.923 (Min 0.970 Max 1.03) Fail
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Second MOT Test after doing a service and cleaning Lamdas
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Natural idle test is a pass
CO Actual value 0.415 (Max Limit 0.5) Pass

Fast Idle Test
CO Actual value 2.083 (Max Limit 0.3) Fail
HC Actual Value 134 (Max Limit 200) Pass
Lambda Actual Value 0.935 (Min 0.970 Max 1.03) Fail
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I bought the OBD Auto Doctor software to try and help diagnosis where the root of the fault is.
I get the following DTCs
17831 P1423 Sec.Air Inj.Sys, Bank1 flow too low
17819 P1411 Sec.Air Inj.Sys, Bank2 flow too low

I'm not sure if this is relevant but on the monitoring section of the OBD Doctor, I get
Bank1 Sensor 1 (O2S)
Oxygen Sensor Output Voltage
Value 0.280v Min 0.080v Avg 0.501v Max 0.850v
Short Term Fuel Trim
Value 1.6% Min -7.0 Avg -2.2 Max 5.5

Bank1 Sensor 2 (O2S)
Oxygen Sensor Output Voltage
Value 0.670v Min 0.435v Avg 0.501v Max 0.680v

Bank2 Sensor 1 (O2S)
Oxygen Sensor Output Voltage
Value 0.085v Min 0.065v Avg 0.409v Max 0.830v
Short Term Fuel Trim
Value -0.8% Min -10.2 Avg -2.7 Max 6.3

Bank1 Sensor 2 (O2S)
Oxygen Sensor Output Voltage
Value 0.625v Min 0.420v Avg 0.693v Max 0.850v


I get these codes on a hand held DTC machine but not on Auto Doctor
17865 P1457 Exhaust gas temperature sensor 2 open/short to B+
17521 P1113 Bank 1 -Sensor1 Internal resistance too High
17539 P1131 Bank2 - Sensor1 Internal resistance too High

I have replaced the spark plugs, oil, oil and air filters, cleaned the lambda sensors, checked the engine pipes for leaks but found this quite hard to do )

Thank you for any help

 

[Samuel c5 Q]

I find Ross tech easier to use and read the results.

 

[Retroman]

Looking at those MOT numbers I would guess you have exhaust system issues. High Carbon Monoxide (CO) is either a very rich mixture or failed catalytic converter - I would guess the latter as the readings are very high. High Lambda in this MOT context is 99% of the time due to a slight exhaust leak which sucks in air during the natural exhaust pulses - the extra air showing in this lambda figure.