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.

 

[Jeide]

I’m sorry it’s been so long since I’ve updated. I’m a bad person. I did get this fixed. I finally took a leap and decided to replace the pcm. I was very impressed with the place I ordered it from. I supplied them with my VIN when I ordered and a couple of short hours later I received an email and a phone call saying that the part I ordered didn’t match the VIN that I supplied and asked which I wanted. I then remembered that a shop had replaced the pcm to fix a transmission problem that I had a while ago. Apparently they didn’t have an exact match. Must have been close because it was running fine. But anyways, I took their advice and got the VIN match. Once I replaced it and programmed my keys, I started it and no engine code for the evap system any more. Truck has a bit more power and much better gas mileage. Thanks to those that helped. And a word of advice. Please don’t go out and buy a pcm just because it solved my problem. As I understand it, the PCM is rarely the cause of a problem. Usually the only way to diagnose it is process of ilimination. I swear by the diagnostic routines in the workshop manuals. The manuals step by step pin point tests are what led me to this conclusion. And even then, I was apprehensive about taking the leap. But it ended well for me and the whole pcm swap was a fun challenge that threw me a couple of curve balls. But I was able to figure it out. I think I’m starting to love this truck.

 

[rumblecloud]

Hello Jeide! Welcome to TRS.
Just found this string and am happy to see you got it all sorted.

I am curious to know where you ended up getting the newer PCM? I think that source would be a great addition to our/my file. They sound like a great resource.

Thanks and don't be a stranger. You sound like an ever greater resource.

 

[Jeide]

Sorry for the late reply and I’m happy to share where I obtained my PCM. I purchased it on-line from a company called Flagship One. I have no affiliation with them other than being a satisfied customer. Their website is Flagship One. I hope this helps someone. Off to start another thread on my mission to get this beast smogged legally in CA