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'01 Accord Failed Emissions Test, Diagnostic Scanner Shows Nothing Wrong

I own an '01 Honda Accord LX with the ULEV engine and 178k on it. My CEL light came on about 6 months ago. Ran the scanner and it showed a P1457 (EVAP Leak). Waited until now when my inspection was due and expected it to be caused by the EVAP shut valve as I read that’s often the cause of the problem with this code. Mechanic said that it can’t pass inspection because of the OBD fail but that the diagnostic scanner showed everything functioning properly, including my assumption about the faulty shut valve. He reset the code and said to drive it the 50 miles for the system to ready itself and bring it back in. As I’ve reset the code several times over the 6 months to see if it would self correct, I’m pretty confident it will come back on. My questions are, is it possible I’ve done damage to the onboard computer by not addressing the underlying problem 6 months ago? Are there emissions problems that are not checked by the diagnostic tool that the mechanic should be looking for? Any information would be greatly appreciated.

If you keep clearing a code, you reset all the monitors to incomplete

Then, when you want to get it smogged, you’ll be rejected for too many failed monitors

It would be a lot easier to just diagnose and fix your evap problem, versus repeatedly clearing the code and getting frustrated

Unlikely that you’ve done any damage by not addressing the underlying problem

That’s sort of my question. If the mechanic is saying that the diagnostic tool shows nothing wrong with the emissions system but the code won’t stay cleared, am I just at his mercy in terms of what he thinks should be fixed/replaced? Or are there problems with the system (i.e a leaky hose or something) that can’t be found with the diagnostics scanner but can be found through some other means (i.e smoke test, visual inspection etc.) thanks again for your input.

I think a visit to a Honda dealer will save you money in the end…The idea here is to pass the smog test as cheaply as possible…


The answer to your question is pretty simple

Pay a competent shop to diagnose and repair your problem. Also ask that they run all the monitors to completion after the repair

That way you’ll know the car is ready to be smogged

BTW . . . here’s a Honda technical service bulletin about that P1457 code.

Great. Thank you both for the info. I really appreciate it.

Many of the higher end diagnostic computers can actually control and activate various parts of the system for testing. It’s hard to say what this shop has done where they’re telling you that their diagnostic scanner isn’t seeing an evap system problem. But obviously you do have one if the code keeps returning. Many mechanics these days trust the computers way too much, but the computers don’t do as much and aren’t as “smart” as many people give them credit for. So all of the above comments stand. Regardless of what this shop claims to be able to see or not see about problems in the system, there is one (or more).

It almost sounds like the mechanic at the smog station was the one that told OP to clear the code and drive 50 miles

It’s quite possible the guy doing the smog isn’t allowed to do the necessary repairs

I believe that might be a conflict of interest