Evap Purge Valve Circuit

[Jeide]

I’ve got a 2000 Ranger with. 3.0 liter engine. After I bought it, I had to replace the engine because the one it came with ave out after 245,000 miles. The new (used) engine has been working out well. After fine tuning things a bit, I am left with one trouble code that is preventing me from getting it smogged. It has a P0443 code, which is an evap purge valve circuit problem. I invented in the power train/emissions shop manual and followed the pin tests in there and came to the conclusion that I need a new PCM. That’s fine, if that’s what it needs. I also downloaded the Forescan software, so I’m prepared for the replacement but I don’t feel like I fully understand how that purge valve circuit works. The main problem that I have with it is that the manual says “

Monitor EVAPPDC PID and voltage between EVAP canister valve signal and PWR GND in output test mode with key ON engine OFF (or in key ON engine running mode). EVAPPDC PID at 0% and voltage less than 1.0 volts (or EVAPPDC PID at 100% and voltage greater than 0.5 volts) indicates a hard fault.

“ I’m not sure if this is something that I can do on Forescan. I did go to the section where I can read the various PIDs and pulled up the output control where I could turn on and off the purge valve. When I metered from the purge valve and ground I got the full battery voltage. Is this where the manual is saying I should see between .5 and 1 volt? If so, what does seeing full battery voltage there mean. I’m planning on replacing the computer regardless, but I would feel better about it if I understood these readings. Thank you if you are able to help.

 

[Josh B]

Hey Jeide, good to see ya man. I can't tell you how to fix it but I wanted to say howdy and good luck with that.
I know someone will be along in time and help you sort it out

 

[Josh B]

May be the timing's off or everyone went to bed early or something

 

[Jeide]

May be the timing's off or everyone went to bed early or something

Myself included. It’s all good. I can be patient. Thanks for the kind words Josh B

 

[Terrys87]

I had an 02 truck that I caused Evap Canister problems. I would fill the fuel tank with every drop of fuel I could get into it. That was a mistake. Due to emissions the vapor line runs into the canister. When you fill it that full, you are running liquid fuel into the canister. Now when the gas pump kicks off, you can round up to the next dollar or so.

On the other end of the fuel situation. With these in tank pumps, fuel is actually a cooling for the fuel pump and running the pump out of fuel shortens the life of the pump. Pumps never completely quit until you are at a filling station with a full tank of gas. Ask me how I know.

I cannot help you with the test, but I will say in general the Evap system is really good. Usually it is problems caused by over filling. When I had my canister issue, I wound up replacing canister with the circuits in it. I would bet your PCM is good.

 

[Josh B]

I fill up by leaving the nozzle locked in place till it pops the latch and that's where I leave it

 

[Jeide]

I do the same when I’m filling up. I’m keeping track of my mileage and I let the pump tell me when it’s full. The very first thing that I did when I first got this code and before I did any research was to replace the purge valve, then replace it again because the one I got from the junkyard didn’t click when power was applied. Then again, for the same reason, but a new one which also didn’t click. I don’t think they click when power is applied.
[QUOTE="Terrys87, post: 2025761, member: I cannot help you with the test, but I will say in general the Evap system is really good. Usually it is problems caused by over filling. When I had my canister issue, I wound up replacing canister with the circuits in it. I would bet your PCM is good.
[/QUOTE]
You mean the canister by the fuel tank, right? This is where I get confused about the trouble codes. The way I understand it, P0443 means specifically a problem with the electrical circuit (short/open) that’s preventing the computer from completing the evap vacuum test. If I am wrong about this then I need to expand my search. Thank you for the reply sir.