I keep getting the "gascap" code on my 08 Ram 4.7 4wd. Ive inspected all the hoses, and everything looks clean. I had a crack in my fresh air filter just upstream from the charcoal canister. The filter was full of pebbles and dust. I cleaned it with compressed air, and patched the hole. (It's a new to me truck). On the ESIM valve, the white thing attached to the charcoal canister, I took it off, and cleaned the gasket. I Ohmed it out and I get OL no matter which way I tilt the thing. It has a weighted valve in it, that makes a vacuum seal during the evap test. Does anyone know how to better test this thing? I assume that when the weighted thing slides one way or other, it makes a connection. I read somewhere online that there should be 1 Ohm of resistance (unlike the NVLD system that has 130 Ohms). Nonetheless, I am getting OL, meaning there is no connection. Am I far off base with testing this?

 

the esim switch provides a path to ground as a signal the esim switch is closed. you should have power on the violet/white wire with the key on...if you don't the wire is open...confirm this by disconnecting the pcm C3 connector and ohm checking pin 35 to the esim switch connector. If its open, run a new wire.

if you think the esim switch is bad, replace the part and fresh air filter with it. probably $60.
if you have a scan tool that can display live data of the esim switch...run the engine until the purge valve opens...the vacuum should cause the esim switch to close the switch to change state. without a scan tool...monitor the voltage before the esim switch backprobe violet wire of the connector (leave it connected to the esim) it should drop to zero when the switch closes.
the switch needs vacuum to close so make sure vacuum is present

 

Thank you for the reply. I don't have a scan gauge. I "think" I grasp your reply enough to test it out. I appreciate your thoroughness. My probe leads on my Fieldpiece MultiMeter are too big to probe the esim switch. I don't want to risk cracking it. It's tiny up in there. With the truck running, how would I check for vacuum at the ESIM white thing? Lastly, the gasket on mine is black. All the new ones I've seen pictures of, the gasket is green. I'm not sure if that's just suppliers or not, but honestly, it looks like it's been replaced. Its not dirty on the outside like the rest of the stuff under there, and there are no hose clamps on the hoses leading up to it. I removed the hoses, cleaned them, as the p.o. seemed to do a lot of off roading and there was dried mud under the truck. I've put hose clamps on most of the connectors, including where the hard plastic meets a short section of rubber hose under the drivers front fender. Lastly, I removed the ESIM tonight, cleaned it with rubbing alcohol, shook it up, blew it out with air until dry, and my gascap light went off on it's own for the first time in 2 weeks. Weird. No codes showing on odometer display.

 

monitor it. the evap monitor can take up to one week before it tests and either passes or fails...time line depends on test conditions.