miguel11691

P0170
0420
0720
0700

GhostAccord

P0170 - Not a listed Honda diagnostic code

P0420 - catalyst system below efficiency threshold = Failed Secondary O2 sensor or Catalytic converter. More than likely the O2 sensor or it can also sometimes be caused by a small/large hole in the exhaust before the secondary O2 sensor.

P0700 - General Transmission diagnostic trouble code. This shows up with any transmission DTC issue. It was triggered by the P0720 code.

P0720 - A/T - Counter shaft speed sensor fault.

Lost Again

I see the P0170 as a temp DTC

GhostAccord

How did I miss that one, it's on the top of every one of my OBD2 lists as well....... :headshake: Ooops!

I notice that it also comes up as a temp DTC for a possible fuel issue..... might that have something to do with the P0420 as well?

seanbev24

OP- do you have access to a scan tool that can show live data? An easy check is to compare the upstream and downstream o2 sensors. If the downstream o2 voltage is switching high/low/high/low like the upstream sensor, the cat isn't doing its job. With a working cat, downstream o2 voltage should stay relatively steady.

miguel11691

i went to my mechanic and he said the cat was trash... it was making so much noise when he moved it... bought a new one for 200 from autozone direct fit... hope that helps... and with the P0170 how can i fix that... is that fuel injection?

ricebike

reset the computer and see if the codes return after you have replaced the cat first...

Lost Again

We are human.....

All I meant by that was to be sure the OP had the info.

Looks like a pending code until the PCM figures out exactly what the issue is ......something is wrong but I'm not exactly sure yet?

ricebike

so that column of temporary codes can be erased when he resets the car's computer?

I always make a habit to write down the codes, clear the computer, then see if the same codes return...

seanbev24

I'd rather just diagnose a problem immediately instead of clearing codes and waiting to see if they return. Go after the cat code first. Once that issue is fixed, clear the codes and look at the live data. Short/long term fuel trims and o2 sensor readings will tell you if there's still a lean or rich condition to worry about.

ricebike

he did went for the cat code first... plus miguel probably doesn't have a scanner that can look at the live data

if he resets the computer and see if the same codes return, then he can move on with his current dilemma. That's why you jot down the codes in the first place

that 0170 lean condition could have been an exhaust leak at the flange between the cat and downpipe... having a new cat installed with new gaskets may clear it up since that's a temp code to begin with

seanbev24

Sorry I wasn't paying enough attention about the cat already being diagnosed. It shows on the chart that p0170 code is a pending code for either rich OR lean. It would be helpful to figure out which one it is so you can make comparisons after the cat replacement.

miguel11691

I will let you guys know tomorrow what happens... I'm getting the cat put in tomorrow in the morning.. wish me luck

FinzWake

Good morning all. I have to ask: how did you obtain the codes above? Do you have one of those scan devices?

I love tinkering with cars and if I were able to do such diagnosis, I would be one happy camper.

I realize this is a tangent to initial conversation but any input on these scanners/diagnostic devices? Where to buy? Pricing?

We are a family of Hondas if that makes a difference

Thank you

liltex

I recieved a P0420 cat code when my car had 145k 1 tank of gas later the code erased itself. At 175k I got the code again and it did not go away this time I read the forum and decided to replace the O2 sensor in the Cat before replaceing the Cat, and the code did not come back saved me a bunch of $$$. Just so you know it's not always the cat sometimes the code points to the problem...