Hi All,

Wanting to know if anyone has come across this p0171 error before and the possible fixes. The car drives fine, probably down on power but hard to tell really. The error occurred when I had my decat system fitted so I believe that the lamba has probably got clogged up or something.

The car is now standard nothing except a BOV, K&N panel filter and a Prodrive cat back.

So far I've changed the MAF and checked for leaks. No leaks can be seen on any of the intake pipes.

I've got a lamba sensor and I'm thinking that this is the problem.

Any more ideas?

Cheers

 

Might be lambda due to decat

 

The car no longer has the decat so it's possibly that the lamba sensor has got clogged up.

 

 

Reset the ecu? Fuel trims will be miles out if you've changed from decat to cat

 

How do I reset the ECU? Also the light EML came on a few days before i fit the cat again.

I've cleared the code with the OBD2 scanner. Drove around for a while then the light comes on.

If I leave the car idling for 15 minutes nothing come up. No pending issues. Only seems to come on once I'm driving around.

 

are you sure you don't just have an air leak somewhere? what are the A/F corrections sitting at when idling and when driving? Is your AFR moving too lean/too rich when driving?

 

From what I can see I can't find any air leaks. I had the car idling for 15- 20 minutes and the error never appeared in the pending faults section.

I then went for a little drive. Never went about 2750rpm and after 10 minutes the fault code appeared in the pending section.

I've checked the hoses and I can't see anything. I'm going to check again on Saturday.

I've checked the hoses to the the BOV and they are Ok. Only thing I've not checked are the hoses to the back of the Boost gauge. Again that will need to be done this saturday

 

you need some computer powers on there to see what the maf/o2 sensor readings are though - this will help you determine if it's an electrical fault or a mechanical fault.

 

The only thing I can think of is that the lamba sensor is buggered due to the decat. I never fit a spacer for the sensor so it's possible that it's clogged up. I'm just hoping that others have more ideas.

Only reason I suspect that is because the car drives fine and idles fine. So it's exactly the same as when I've had decats on other cars that throw up the error for too lean before I bought the space for the lamba sensor.

 

the o2 sensor in the headers wouldn't be affected by the cat/sportscat/decat though so not sure how it would get clogged up by something behind it in the exhaust stream. If the car is seeing lean then yes the sensor could be dead (unrelated to the presence of a cat/sportscat/decat - but perhaps because someone knocked it when fitting bits) but live data would show you this.

 

I mean the sensor after the cat that might have been clogged up.

 

nah you'd get a code for cat system efficiency below threshold then. A/F corrections are mainly handled by airflow metering and primary o2 sensor in the headers.

 

If I had the car remapped would this stop the code from appearing?

 

is it appearing because of the map? or a faulty sensor? or a leak? if it's a map problem then remapping will fix. If it's a sensor problem then the sensor needs replaced. If it's a leak then the leak needs fixed.

The code your getting seems to indicate a leak or faulty sensor so I'd get those checked out first and then when the car is tip top get it mapped up to release the full potential of your new parts.

 

No the car is standard. Tomorrow I'm going to check the front O2 sensor by the drivers wheel and then check the other lamba where the cat is.
Pull off the top mount and see if I can see anything else. All the pipes and hoses seem fine. Can't see any cracks in them.

Only thing I can think of is that that the front O2 sensor is bust.