C1340 and P0420 Engine Codes

[phishtaco]

I searched the code numbers here. C1340 anyone know what causes/fixes this? P0420 looks like gas cap which has been replaced but it may have been aftermarket. Thanks

 

[HomersCanyonero]

P0420 is not the gas cap.

 

[OutoftheMud]

I believe P420 is drivers side catalytic converter efficiency issues. Just went through this on my 03 4Runner. You can run rear 02 simulators to clear this code, or replace the cat.
The C1430 I got occasionally when i had a pretty bad vacuum leak, at the time I had like 15 codes when the vacuum hose came off. But the C1430 was one of them, thats all got.

 

[GXer04]

Check for exhaust leaks in joint post cat before the 2nd O2 sensor. Probably drivers side, but check both. A leak there will tell the system the cat is bad.

 

[JLee]

I searched the code numbers here. C1340 anyone know what causes/fixes this? P0420 looks like gas cap which has been replaced but it may have been aftermarket. Thanks

Did you have any luck?

Here's my saga: C1340 - Open Circuit in CDL signal - ClubLexus - Lexus Forum Discussion

 

[phishtaco]

Did you have any luck?

Here's my saga: C1340 - Open Circuit in CDL signal - ClubLexus - Lexus Forum Discussion

I have not addressed it. My CEL will go on for a few hundred miles then off. I’ve meaning to do a zero point calibration on it. I know the PO had a gasket? changed on the tcase, I need to look back at the records.

 

[fourleggedfish]

I have not addressed it. My CEL will go on for a few hundred miles then off. I’ve meaning to do a zero point calibration on it. I know the PO had a gasket? changed on the tcase, I need to look back at the records.

I was getting a P0420 on my 4runner with Cali emissions and thought I had to replace both cats. Got a quote for OEM from the dealer and they came back with $4,300 for cat back.

I ended up replacing both upstream and downstream O2 (F/A) sensors and the code disappeared. It might be worth a shot, given the O2 sensors were around $85 ea.

It’s been a year and P0420 hasn’t come back (except after I replaced a blown engine, which blew clouds of white smoke on first start, but the code cleared after a day).