Check engine light for EVAP
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4wd High
Joined: Dec 2023
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Check engine light for EVAP
I have a 08 F250 with the check engine light on. Codes are P0451-Evap emission system pressure sensor / switch range/ performance. P1450- fuel tank vacuum cannot bleed. P0457- Evap emission system leak detected (fuel cap loose/off). I'm starting with the vent valve. I have 12 volts at the harness but valve is open. I hooked the valve directly to the battery and it shuts with the same voltage. I used my test light on the harness plug, no light but my meter reads 12 volts. The harness is just a 2 wire so I am assuming one is hot and one is a ground. Both wires appear to be the same color. I hooked my light to a new ground and now it lights up. Meter reads the same with the new ground. So do I have a bad ground for the vent valve? Anybody know of a site to get a wiring diagram? I want to make sure one is a ground before I tie into it with a new ground. There is a frame ground close so I am going to tap into it for a new ground. I cleaned the gas cap area with a wire brush head on my drill and now I am going to test the purge valve. I'm hoping these fix the issue because I'm not looking forward to dropping the tank to get at the pressure sensor.
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4wd High
Joined: Dec 2023
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I just checked the purge valve and it's the same situation as the vent valve. Works with a new ground. I must have a bad ground somewhere on the truck. I'm willing to bet the pressure sensor is doing the same thing. Everything else on the truck works as it should.
Hotshot
Joined: Jan 2004
Posts: 19,767
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From: St Louis
The grounds for the solenoid valves are supplied only by the PCM under software control. If the PCM isn't commanding them to be closed, they will be floating. Leave the ground circuits alone unless you actually know you have a fault.
Start by checking to see if the purge solenoid is stuck open. Leave the vent valve alone for now.
Start by checking to see if the purge solenoid is stuck open. Leave the vent valve alone for now.
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