My Disco has started throwing a P1170. I replaced the front 02 sensors a couple months ago. I have read that many times this code means your cats are bad? Is that true? I saw some who fixed the code with new 02s, others not so lucky. Any ideas?

 

could also be a cracked weld at the cat...or a vacuum leak, but that's will throw p1171/p1174 codes

 

Engine Code: p1172

Land Rover Engine Code: P1172 = Rich Fueling Fault

Click to Process more Land Rover Engine Codes here

leaky or sticky injector?
Restricted air flow?

 

Could be bad O2 sensors, but it seems that more people fix this code by finding and repairing a vacuum leak or replacing the MAF. Cleaning the MAF sometimes works also. Other possibilities are cracks or leaks in the cats, or I read one post where the code was fixed after two clogged injectors were cleaned.

I'd start with the easy stuff. Confirm that there are no leaks at the cats. Swap the sensors from side to side and see if the code follows them. Pull the plugs and check to see if they are showing consistent coloration. Try doing a smoke test to look for leaks (there was a post not too long ago about doing this with a rubber glove and a cigar). If none of that works, try cleaning the MAF.

 

1170 is a code for a slow O2 sensor. The system checks them in various ways. It also checks the cats by comparison on the up and down stream O2s, and if storage capacity of the cat is exhausted it throws a code 420 or 430. Since 1170 is detecting a slow repsonse in recognizing a rich shift (by more than 1 second), it (and plenty of other codes) can be "fooled" by things like vac leaks, etc. If you download the Bosch ECU manual they have a technical discussion of O2 monitoring, etc. Links below, sorry, my copy is about 4 meg, so had to break it up for posting.

 

Thanks guys. Haha sounds like answers are all over the place. I think I will start with the 02s. Would this be the front 02s? or the rear? Like I said in my original post, I replaced the front two not too long ago, but the rear 02s are original still...

 

Just wanted to post a solution to this issue in case anyone runs across it in the future. I replaced the rear 02s and the code has disappeared and she's running great.

 

I replaced all 4 O2 sensors and still get the 1170. I am starting to suspect racked welds at the cat.