P0420 And P0700

[leboyd]

My daughter's truck has 151,000 on it. Recently, it started reporting p0420, p0421 and p0700 (and the phathom ? p1100) with an AutoXray. I say "phathom" because I see that online people say this is not a valid code.

 

I was pretty sure the rich bank 1 and 2 codes were from the fuel pressure regulator. So, I replaced it this weekend, and the rich readings are gone (as well as the slight smell). However, I still have these codes.

 

I think the p0420 is not the catalytic converter, but I have no idea about the p0700 or p1100.

 

Any ideas?

TIA

[luthor]

Basically P0420 Catalyst System Efficiency Below Threshold (Bank 1) - means that the oxygen sensor downstream (after) your daughter's GMC catalytic converter on bank 1 is detecting that the converter is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system. You will likely not notice any drivability problems, although there may be symptoms. This code could have been caused that leaded fuel was used where unleaded was called for, an oxygen sensor is not reading (functioning) properly, the engine coolant temperature sensor is not working properly, damaged exhaust manifold / catalytic converter / exhaust pipe or retarded spark timing...

 

The simplest thing to do is to reset the code and see if it comes back. Next step is to measure the voltage at the oxygen sensor on Bank 1 (the rear sensor, or the sensor after the converter). The voltage should be low and steady (~200mV, depends on the vehicle). If the voltage varies (e.g. 100mV to 600mV) then it's time to replace the catalytic converter. In fact, it would be a good idea to test each oxygen O2 sensor while you're at it. One thing to note is that many vehicle manufacturers offer a longer warranty on emissions-related parts. So if you have a newer car but it's out of it's bumper-to-bumper warranty, there still may be warranty on this type of problem. Many manufacturers give a five year, unlimited mileage warranty on these items. It's worth checking into. By the way, the P0700 code is pretty generic, but I did find descriptions which mention that it could be related to component slippage, a problem with the t-case shift components, a worn or bad TCC circuit/valvebody (which usually leaves a harsh 1-2 shift), or even just nasty fluid. Hope this helps... Good luck!!!