P0498 and P0135. stumped
 

Hey what's going on guys. I'm doing a coworkers car that he just recently purchased. 2005 Honda Accord LX, 4 door 5 MT. 2.4 L 4 cylinder.

I checked that 7.5 amp fuse already, the IGA fuse or whatever it's called, number 23 or something like that. With multimeter. And after looking all over online for information related to this, I ended up convincing my friend to buy a Purge valve that I replaced. Still I come up with the same code. Interestingly the code immediate comes back up right after deleting it, before even starting the vehicle. I wanted to test for voltage at the connector going to purge valve but I can't probe in there with my multimeter, even tried making my own probe with 22 awg wire and still doesn't fit. I have fine probes somewhere. Anyways.

Reading more online and trying to find wiring diagrams so I can find a relay for the EVAP system/purge valve and see if that's causing an issue but all I've found is apparently there's a relay that powers both computer and what feeds the EVAP purge valve. Do you guys have any ideas?

Re: P0498 and P0135. stumped
 

Did you happen to figure it out? I'm running into the exact same problem.

Re: P0498 and P0135. stumped
 

Oh man. I can't remember but I did fix it.

If I have to just take a guess as to what I did, I think I ended up tapping into a circuit that gets switched voltage in ignition switch sequence position 2 or 3 and literally just spliced it to get outta there. There were no issues for nearly 100,000 miles before the car got killed from Hurricane Ida. I remember I ended up following the wires for hours and was never getting voltage to the evap canister in the back. I was checking the car out for a friend, and I wasn't able to fix it at the time. I returned the car to him, and told him, I need to go through the harness and see what's going on, but "theoretically if you splice into this circuit or this circuit then you would have the switched voltage that you would need". He then had one of his mechanic buddies do probably just what I had described but never fully confirmed to me what he actually did workwise that remedied the situation (because he's a shady f*ck).

Basically at the end of the day, if you pull the connector at the purge valve in the back, you will most likely find that there is no voltage going there. As far as implications for wiring the purge valve as "always on" with switched voltage as I've described, that so much I couldn't tell you but. I would probably assume that the ECU is supposed to act as the switched voltage and determines when it is supposed to activate the purge valve and evap system. If I remember, I believe it's a 3 wire connector going to the back which would kind of mean to me that one wire would be going to a control circuit that verifies the ECU that the evap is getting voltage and thus you could trick the ECU to turning the MIL off if you bring 12 volts to that circuit from elsewhere. Looking back on it now, I wonder if locating the ECU and simply removing the wire going to the evap canister and putting it back in/cleaning contacts would have worked, after tracing the wires and verifying continuity/ohm test on the conductor itself would have been better. I think I started reading from some people back then that you'd need to change the ECU because the ECU sends voltage for the EVAP control circuit or something (f*ck that), or so I was reading. Overall, I don't know much about these cars and this has been a while ago and some of my information may not be correct, and splicing into other circuits to power things such as evap components is not typically something I would recommend.

I would start by checking voltage at the connector for the purge valve/canister (sorry I'm rusty lol!) underneath at the back of the car first and verifying that you have no power there. That triggers the MIL. Then you'll see that it goes to a harness that sucks to get to and etc. Verify where this circuit gets power (which I believe is from the ECU but I'm not 100% sure). Refer to wiring diagrams and whatnot. If this is the case, pull the ECU and clean the terminals and stuff. If you cannot locate the exact wire, which would be cumbersome, then spray contact cleaner in there on all the contacts and if you don't want to do that, then simply disconnect and reconnect a bunch of times so the terminals "scratch" and make good bonding contact again. If this does not work, then perhaps go full butch mode and refer to unconventional methods, perhaps steal power from a different circuit, that gets activated on ignition switch so it's not on when the car's not in use and tying to the positive on that circuit, and the ground should ground back out on a shared ground anyways.

I'm more of a volkswagen guy, and I don't know the specifics of when the EVAP control circuit is triggered. I do know on VW's on the same years the circuit is triggered simply by opening the doors and whatnot but they have a more extensive immobilization circuit and perhaps they felt it was a good idea to trigger the EVAP when the doors opened. I don't know the specifics of the Honda EVAP circuit and triggering, cycling frequency and etc on these cars but if somebody had a breakdown of that, that would be awesome

Hope that helps!

Re: P0498 and P0135. stumped
 

Mine was the fuse under the hood not the dash. Forgot about the 2nd fuse box.🤦‍♂️

Thanks for your help and replying!