Check engine P2420

Title says it truck threw a check engine light 2015 V6 off road. code is P2420 Evap switching valve control circuit High. I just don’t have a good enough understanding of the system. Some people said a gas cap fixed it… how can that fix the high voltage issue of the valve?

I checked the purge valve seems to be working no vac on start up then after a few mins there is a vacuum there. I was going to start with the gas cap, I just don’t know why a leaking gas cap wouldn’t throw a leaking code with a pressure test.

 

P2420 isn't a circuit code, it's a logic code. It means the ECM isn't seeing a pressure change when commanding the vent valve during an EVAP check.
Doubtful a gas cap would fix it, be aware aftermarket gas caps generally do not work well on Toyotas.

Could be wiring, the Canister Pump Module, or a clogged vent.

The Vent Valve gets ignition Power on Pin 5 (Blue/White) of the Canister Pump Module connector, Ground is Pin 1 (Violet/White) and is controlled by the ECM.

 

okay so if the valve were to close and there was a leak like the gas cap it should fire a P0442 or a P0445 code…

thanks for sending the pages for the service book. Man I wish I had that handy all the time!

 

Typically a gas cap or other leak will set P0441, P0455, and/or P0456 codes.

While it's called a vent valve on these it does not seal the system when closed, while I'm not sure exactly how it works inside I know it's used to switch between drawing air through the reference orifice and through the vapor lines during a leak check.

Why Toyota uses this instead of a standard Purge/Seal/NVLD EVAP system I don't know but it's what we have.

 

thanks for the help I’m getting a better understanding of the system. Appreciate the PDFs. I guess I’ll start with a 20$ Toyota cap and move on from there. I’ll crawl under the truck tomorrow to see what I can see.

Strange thing is all these say when the truck has been off it runs these diagnostics, the CEL fired while I had been driving for awhile.

 

Don't know the logic of turning on the CEL but the EVAP test runs with the truck off and it is a 2 trip code meaning it has to fail twice in a row to set the light.

 

Wonder what determines the code for a gross leak vs valve stuck open. Would imagine a valve open would create a large leak. Looks like maybe the difference in no pressure variation (open valve) vs deviation from reference pressure (leak). Probably means unless the gas cap isn’t holding any pressure it won’t be that.

 

Step 1. - Do you have emission testing in your state?
If No, Problem solved.

Wouldn't surprise me if it waited until it completed a purge flow test to set the CEL.

 

Unfortunately in Tucson we do but not everywhere in Az.

 

It's all in there if you can decipher it but again the valve does not close the system, it switches between drawing through the reference orifice and drawing through the system.

It draws vacuum through the reference orifice to get a reference pressure for the leak threshold then through the system to determine if it has a leak if that makes sense.

 

Pressure difference between step 3 and 5.
If 3 is greater than 5, Gross leak.


Not going to lie, these EVAP diags are not the easiest to read or navigate.

 

Yeah that’s what I was looking at and stuck is zero pressure change.

 

yeah I see that now 1st time looking at these diagrams a little confusing.

 

Looks like the valve and charcoal canister is all 1 part. 77740-04030. Guess I’ll be looking at wires tomorrow.