Failed my MOT on emissions

[goodbuzzman1]

So today i failed my MOT on emissions on low idle.


I have 3 fault codes which i realise are directly causing this

1. 16804 - Catalyst system bank 1
P0420 - 35 - 10 Efficiency below threshhold

2. Exhaust Gas Temperature (G235)
P1453 - 35 - 10 Open or short to plus

3 Oxygen (Lambda) Sensor B1 S2
P1114 - 35 - 10 Internal resistance too high

This afternoon i checked for continuity between pins 1 & 2 on the EGT plug, back to the ECU and i have continuity. I didnt check the blue/yellow...should i?


I suppose my real question is, is the EGT fault causing the other two fault? or vice verca, what should i replace first

thanks

 

[Lewis583]

Likely yes. With a EGT fault stored in the ecu it dumps fuel into the cylinders as a safety precaution because it cannot take a reliable reading from the EGT sensor. With the excess fuel comes, damaged catalytic converter/bore wash in the cylinders which can cause excessive piston ring wear.

You tried clearing the faults to see if it returns?

Yes you should check continuity of all wires. You have continuity but what was the resistance reading? Anything below 0.3ohms is ok, above that and you have an issue in the loom.

 

[goodbuzzman1]

Likely yes. With a EGT fault stored in the ecu it dumps fuel into the cylinders as a safety precaution because it cannot take a reliable reading from the EGT sensor. With the excess fuel comes, damaged catalytic converter/bore wash in the cylinders which can cause excessive piston ring wear.

You tried clearing the faults to see if it returns?

Yes you should check continuity of all wires. You have continuity but what was the resistance reading? Anything below 0.3ohms is ok, above that and you have an issue in the loom.

yeah ive cleared it before and it keeps coming back. I have had running issues with car since I bought it and everything points towards this.

Can you tell me where to take the resistance reading from?

and from what I read, the blue/yellow wire joins into a load of other ones somewhere in the loom... Is there even an ecu pin to check?

 

[Lewis583]

The same place you tested continuity for the 2 wires. Use a multimeter set to measure resistance/continuity and measure between EGT sensor connector and ECU connector.

Check for voltage at the Blue/yellow wire at the EGT sensor connector. If it is on the same circuit as the maf/o2 sensors (which I suspect it will be) you should see battery voltage when the igniton is turned on. If not then that wire is open circuit and seeing as you have no MAF/o2 sensor codes, it would be after where the loom joins.

 

[goodbuzzman1]

ok ill check it out tomorrow.... although i did get the o2 code Oxygen (Lambda) Sensor B1 S2
P1114 - 35 - 10 Internal resistance too high

 

[goodbuzzman1]

Check for voltage at the Blue/yellow wire at the EGT sensor connector. If it is on the same circuit as the maf/o2 sensors (which I suspect it will be) you should see battery voltage when the igniton is turned on. If not then that wire is open circuit and seeing as you have no MAF/o2 sensor codes, it would be after where the loom joins.[/QUOTE]

I stuck a meter on the blue and yellow connector today and with the ignition turned on i was getting a tiny bit of voltage, like 0.02v. are you saying i should be getting (12v) battery power?