All Things Mk5 > Performance Modifications
Can fit a standard cat back on to a decatted car?
owheel:
@Jons1001 your codes are really puzzling! Are the lower 2 sensor codes in the picture both relating to bank 1 sensor 2?
The first code means your engine seems to think it's running lean from the data from the sensor upstream of the cat. If both the other codes relate to bank 1 sensor 2, then it looks like that sensor is broken?
Did these throw a CEL on the dashboard?
Sent from my moto g(8) plus using Tapatalk
Jons1001:
--- Quote from: owheel on April 11, 2021, 05:23:16 pm ---@Jons1001 your codes are really puzzling! Are the lower 2 sensor codes in the picture both relating to bank 1 sensor 2?
The first code means your engine seems to think it's running lean from the data from the sensor upstream of the cat. If both the other codes relate to bank 1 sensor 2, then it looks like that sensor is broken?
Did these throw a CEL on the dashboard?
Sent from my moto g(8) plus using Tapatalk
--- End quote ---
Hi mate, tell me about it!
As you can see the bottom one is bank 1 sensor 1. Yes the CEL did come on and has done every 3 weeks or so since the fault occurred a couple of months ago. Really need to get to the bottom of it so if anyone has any ideas would be great.
owheel:
@Jons1001 Do you think it could be a damaged o2 connector or loom if it's an intermittent problem? Maybe it could be that every 3 weeks or so you are hitting a bump just right that is momentarily breaking the connections/causing funny readings? Those codes would recorded but would not affect driving. It would allow you to clear them but they would reappear as soon as the loom gets jogged again. All three codes are related to the O2 sensors, so you have one code for sensor 1 Saying the engine is running lean, and another saying the same sensor is stuck rich and cannot be reached? If the sensor can't be reached, then surely it cannot tell if the engine is running lean or not?
My logic is that if these cause a CEL and you can clear it with out physically changing anything on the car, and it doesn't re appear immediately then the car is not actually running lean and the exhaust is not rich as per the codes, meaning it must be an intermit sensor/loom issue.
Can you read live data with your app? Maybe run the car and see if you can read data from the O2 sensors and see if you are getting signals?
I want to stress though that I am not a professional mechanic, I'm just using my experience from working with sensors at work. If anyone knows more than me I am happy to be educated!
Sent from my moto g(8) plus using Tapatalk
Jons1001:
Yes interesting thoughts. Im having the thermostat done next week so will ask the mechanic to take a look and see if he can see anything untoward with the O2 sensor/connectors/wiring. Not sure if i can access the live data, I have a basic version obdeleven and while it does have live data on the menu it looks too technical to use for someone like me.
I take it though that it could also be to do with the remap as if they say it was mapped to have no restrictions and I have now placed a restriction there this could cause these codes?
pudding:
--- Quote from: Jons1001 on April 11, 2021, 12:54:05 am ---I cleared the codes but they have returned 3 times now after about 3 weeks each time. I contacted the company that remapped it and they said the codes would be because the car was mapped as having no restrictions and I have placed a restriction there (the cat) so would need to have the map tweaked at a cost of £150.
--- End quote ---
In other words, £150 to change 1 byte in the map. Downstream O2 = off, which essentially turns off the catalyst efficiency CEL. Which is illegal, being anal about it.
Bank 1 S1 is the primary sensor and the only one you need to give 2 sh1ts about. That one should never fault code. 'No signal' is a significant fault that needs investigation.
B1 S2 can do one as it's just there to monitor cat efficiency.
OEMs such as Toyota also use the downstream O2 to trim long term lambda %, but I don't belive that is the case with VW EA113 engines.
An aftermarket 100 or 200 cell secondary cat is not going to add a restriction worth worrying about. Hybrid or big turbo conversions that are more sensitive to back flow restrictions perhaps, but not the puny OEM turbo.
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