2007 5.4L P0446 - very low voltage - green wire
03-13-2018, 06:41 PM
#1
Weekend Mechanic
Thread Starter
2007 5.4L P0446 - very low voltage - green wire
Hey guys,
I have a 2007 F150 5.4L with a CEL throwing P0446.
I have the wire diagram and pinouts for the canister valve circuit so I dropped the spare tire and disconnected the canister valve solenoid to check voltage. I am reading bouncing 0.2v-0.5v from the green wire to a bolt through the frame for ground. If I understand the diagram correctly, the green wire to the plug should have 12v+ constant from the batter even with key off. The F5 (7.5a) fuse is good so there is likely something going on with the wire in the harness somewhere. I don't want to unwrap 20 feet of wire loom and it looks pretty intact all the way to the cab under the driver's side. However, there is a plastic cover under the drivers door that provides some protection for a couple harness connections. This cover was full of dried mud and dirt that was all up in the connections. I think this may be the cause of the voltage loss.
I haven't check for resistance in the harness because I don't have a lead wire long enough, but with the low voltage and fluctuations, I'm betting there is a ton of resistance in that wire.
Enough with the background. My question is: Is it safe to disconnect the wire harness on the frame under the driver's door with battery connected? I want to check for batter voltage at the connector to determine if the short is before or after the point at which it goes into the cab.
Once I get voltage back where it should be, I can test the solenoid. But this low voltage would definitely throw the 446 code.
(Not my truck, but here's a pic of the wire harness location)
http://lh6.ggpht.com/-zOEep-fJ44g/Sl...5B1%25255D.JPG
I have a 2007 F150 5.4L with a CEL throwing P0446.
I have the wire diagram and pinouts for the canister valve circuit so I dropped the spare tire and disconnected the canister valve solenoid to check voltage. I am reading bouncing 0.2v-0.5v from the green wire to a bolt through the frame for ground. If I understand the diagram correctly, the green wire to the plug should have 12v+ constant from the batter even with key off. The F5 (7.5a) fuse is good so there is likely something going on with the wire in the harness somewhere. I don't want to unwrap 20 feet of wire loom and it looks pretty intact all the way to the cab under the driver's side. However, there is a plastic cover under the drivers door that provides some protection for a couple harness connections. This cover was full of dried mud and dirt that was all up in the connections. I think this may be the cause of the voltage loss.
I haven't check for resistance in the harness because I don't have a lead wire long enough, but with the low voltage and fluctuations, I'm betting there is a ton of resistance in that wire.
Enough with the background. My question is: Is it safe to disconnect the wire harness on the frame under the driver's door with battery connected? I want to check for batter voltage at the connector to determine if the short is before or after the point at which it goes into the cab.
Once I get voltage back where it should be, I can test the solenoid. But this low voltage would definitely throw the 446 code.
(Not my truck, but here's a pic of the wire harness location)
http://lh6.ggpht.com/-zOEep-fJ44g/Sl...5B1%25255D.JPG
