Hello,
I've had the CEL on for months now and am finally trying to figure out how to fix it. First, I got a OBDII coder reader and got that P0446 code. Searching around on the internet I could see that it might have several causes. I took a stab in the dark and replaced the purge valve with no luck. Replaced the filler cap again with no luck. I finally got under the truck and removed the cannister to see if it was plugged- it seemed ok, since I could blow through it with my mouth. I tested the vent solenoid valve using a power supply- it clicked and closed off ok. The wiring and hoses all look ok from what I can see. I figured that the EVAC test must be performed with every startup since that's when the CEL comes on after clearing the code, so I rigged up a test jig consisting of a red LED and a 470 ohm resistor and plugged it into the vent solenoid plug and had my brother start the engine- I didn't see any action, so I'm thinking that either the wire is broken somewhere which seems unlikely, or the computer isn't grounding that line. So I need to check the pin on the computer to see if it goes to ground to eliminate the wiring as a suspect. But of course the computer is buried under the passenger's side kick panel. Can somebody tell me how to identify which pin or connection I need to test?
Regards,
Chet

 

Welcome to the forum

You should always look up trouble codes on a FULL LIST, like here: https://therangerstation.com/tech_li...II_codes.shtml

So you can see all the codes the computer can choose from, the codes it does NOT use are as helpful as the code it DID use
Partial list here:
P0440 Evaporative Emission Control System Malfunction
P0441 Evaporative Emission Control System Incorrect Purge Flow
P0442 Evaporative Emission Control System Leak Detected (small leak)
P0443 Evaporative Emission Control System Purge Control Valve Circuit
P0444 Evaporative Emission Control System Purge Control Valve Circuit
P0445 Evaporative Emission Control System Purge Control Valve Circuit Shorted

P0446 Evaporative Emission Control System Vent Control Circuit Malfunction
P0447 Evaporative Emission Control System Vent Control Circuit Open
P0448 Evaporative Emission Control System Vent Control Circuit Shorted

P0449 Evaporative Emission Control System Vent Valve/Solenoid Circuit Malfunction
P0450 Evaporative Emission Control System Pressure Sensor Malfunction
P0451 Evaporative Emission Control System Pressure Sensor Range/Performance
P0452 Evaporative Emission Control System Pressure Sensor Low Input
P0453 Evaporative Emission Control System Pressure Sensor High Input
P0454 Evaporative Emission Control System Pressure Sensor Intermittent

Circuit malfunction means its not a leak, so not hose related

P0446 Evaporative Emission Control System Vent Control Circuit Malfunction

So the computer has detected the Vent circuit is out range or not connected, its a solenoid so just a coil of wire with low OHMs, if ohms are high(no connection) or low(short), BUT, compter has codes for Vent circuit OPEN and SHORTED which it did NOT use
Yes, could be the coil itself is bad(the solenoid), so not a bad decision to just replace it on speculation

Engine Computer(PCM) is in the upper firewall in engine bay, 1995 and up Rangers
SJB(body computer) is in the passenger side kick panel on 2004-2011 Rangers

PCM has a 104 pin connector

Google: ford ranger pcm pin numbering

About all you can do is to test continuity of the PCM to Vent wiring, you can test solenoid ohms, should be under 20 I would think
If wires are OK then problem is inside the Computer

 

RonD,
Thanks for the help- I found the broken wire at the transmission crossmember where it had apparently chafed and corrosion had eaten the wire completely at that spot. I found it because another person with a 2.3L had this problem and so I took a good look at that area- I had to dismount the connector to expose the damaged part. Spliced it back together and the problem is gone.
Chet