Working through deferred maintenance on this new to me 2008 Type-S 6MT. P0499 CEL has been on for a month or so since I got it and I believe for a few years now. I have been scouring here and the internet but have not found much information on common problems or resolutions related to this. One account was fixed by replacing the ECM. Does anyone have an idea where to start with diagnosing/troubleshooting this code? Thanks for any insight in advance.


From DTC Decode:
Make:Acura
Code:P0499
Definition:Evaporative Emission (EVAP) Canister Vent Shut Valve Control Circuit High Voltage
Description:If the return signal is ON when the Powertrain Control Module (PCM) outputs the OFF signal to the EVAP canister vent shut valve, the PCM detects a malfunction. The execution time is continuous and the duration time is 5 seconds or more. DTC P0498 is not active. The return signal is ON for at least 5 seconds when the PCM outputs the Low signal to the EVAP canister vent shut valve. NOTE: Before you troubleshoot, record all freeze data and any on-board snapshot.Cause:

• Poor connections or loose terminals at the EVAP canister vent shut valve and the PCM
• PCM may need to be updated with the latest software
• Faulty PCM
• Faulty EVAP canister vent shut valve

 

Test the valve. If valve is malfunctioning, replace purge valve.

 

Is it just a +12v on/off type valve? I ask because low voltage PWM valves do not like it when you blast them with constant 12v.

 

here's what it says in the service manual.

 

Wow, so poor connection or bad ECM ($$$). Interesting that it does not point to the valve at all. Thank you for the information. Extremely helpful!!

 

Vent valve is in the canister under the car, not on the engine. If you unplug it and measure resistance it might give you an idea what's going on. That valve is basically an electromagnet, so I would expect it to have resistance 20-30 ohm. If it's completely open or shows something high like >200 ohm vent valve is probably bad.





It should have key-on power on one wire and grounded control by ecm. You won't be able to test the ground control without bi-directional scan tool/

So measure valve resistance when disconnected, and check if it receives power on that one wire. If it has ~25 ohm, and has all time power, and ground control wire checks out from ecm connector to the vent valve connector, then if fact ECM might be bad.

 

Wow, you guys ROCK! Thank you for the detailed insight and direction to get started. I’ll let you all know what I find when I get the time to dig in. Got to do valve cover seals, and valve adjustment while I’m there, first. Then off to the front end clunks. Down the rabbit hole we go! Haha.