P codes

[killj0y]

Ok so I've always had the following p codes and honestly I've read up on them many times and have come up empty or any attempts to diagnose have been unfruitful. So could a few experts chime in. The truck runs good and no cel so I've had it on the back burner.

P0443
P0401
P0420

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[Mazda]

I'm certianly not a expert on these but P0443 shows their is a problem with your purge valve, wiring, or hoses that connect to the valve.

http://repairpal.com/obd-ii-code-P0443

The other two codes will most likely go away after repairing the P0443 code.

I think I will let RonD show his knowledge on this.

 

[adsm08]

As Mazda said, the 443 is related to the circuit for the evap purge valve. The purge valve is the one on the intake. It is a circuit fault code, so it means there is an open wire somewhere. That somewhere could be in the valve itself.

Generally the test for this code is to place a small light bulb in the circuit, in place of the valve, and then command the valve on, see if the bulb lights up. I'm guessing you don't have a scanner that does active commands though, so I'd start by resistance testing the valve. It is on the line between the carbon canister and the intake, kind of a cylinder looking thing.

P0401, insufficient EGR flow detected. 90% of the time this code means the DPFE sensor has failed. It is a fairly sensitive unit that live in a very harsh environment. It's bolted to the intake near the EGR valve.

The P0420 is catalyst efficiency below threshold, bank 1. This is always a bad cat.

Since you have no check engine light, and all of those codes would cause a light, first I'd make sure the light works. If it comes on when you turn the key to run, the light works. If it does, I'd clear those codes and see if something comes back before going forward.

 

[Mazda]

P0401, insufficient EGR flow detected. 90% of the time this code means the DPFE sensor has failed. It is a fairly sensitive unit that live in a very harsh environment. It's bolted to the intake near the EGR valve.

I don't know about the DPFE on your 96 but on my 94 the hoses would sometimes come off. (Happened both times I had my clutch replaced, the guy would somehow knock them off) Also check if they are brittle or cracked as they get a lot of heat from the EGR pipe.

Here is a good site on how to test the DPFE

http://easyautodiagnostics.com/ford/4.6L-5.4L/how-to-test-the-egr-system-1

 

[killj0y]

As Mazda said, the 443 is related to the circuit for the evap purge valve. The purge valve is the one on the intake. It is a circuit fault code, so it means there is an open wire somewhere. That somewhere could be in the valve itself.

Generally the test for this code is to place a small light bulb in the circuit, in place of the valve, and then command the valve on, see if the bulb lights up. I'm guessing you don't have a scanner that does active commands though, so I'd start by resistance testing the valve. It is on the line between the carbon canister and the intake, kind of a cylinder looking thing.

P0401, insufficient EGR flow detected. 90% of the time this code means the DPFE sensor has failed. It is a fairly sensitive unit that live in a very harsh environment. It's bolted to the intake near the EGR valve.

The P0420 is catalyst efficiency below threshold, bank 1. This is always a bad cat.

Since you have no check engine light, and all of those codes would cause a light, first I'd make sure the light works. If it comes on when you turn the key to run, the light works. If it does, I'd clear those codes and see if something comes back before going forward.

I'll try the bulb thing for sure. And yea I have a multimeter, working on getting a power probe any budget recommendations on one? Lol

The DPFE sensor has been changed 3 times it's under warranty so I could try again. I even removed and cleaned and reinstalled the egr valve.

The cel works I have leds so the likely hood they failed isn't high I'll check to make sure it's still operating. I've cleared the codes many times they come back. I have a Bluetooth adapter always connected. So should I look into getting a new cat? I put in new o2 sensors already. The purge valve sensor is new as well. I think that's what it's called. Like I said it's been going on for a while little by little eliminating items.


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[killj0y]

I don't know about the DPFE on your 96 but on my 94 the hoses would sometimes come off. (Happened both times I had my clutch replaced, the guy would somehow knock them off) Also check if they are brittle or cracked as they get a lot of heat from the EGR pipe.

Here is a good site on how to test the DPFE

http://easyautodiagnostics.com/ford/4.6L-5.4L/how-to-test-the-egr-system-1

Well they are silicone hoses thick one kinda, and they are in good shape. In fact they are kind of a pain to get off the sensor so they dont come loose. it it worth trying to replace it again? Like i said earlier its been swapped 3 times with new units thinking i got duds.

 

[Mazda]

Okay let me give you one more thing to try. It's a long shot but I did this and it solved my problem when I was getting these or similar codes before.

Unplug and remove the EGR Valve Vacuum Solenoid. Take the cap off and clean it out. blow a little air thru it. Not to much pressure. A computer air can will work. Reasemble and see if that changes anything.

As I said it worked for me after changing the DPFE and following the steps in the link I posted before.

Also maybe disconnect the neg and positive cables over night just to be sure it clears everything. Reconnect the cables in the morning and see what happens.

 

[adsm08]

Yeah, the DPFE isn't the only potential culprit. If the vacuum switch isn't doing it's job, or if the vacuum lines are damaged, the valve won't open, or won't open as far as it should.

 

[killj0y]

Okay let me give you one more thing to try. It's a long shot but I did this and it solved my problem when I was getting these or similar codes before.

Unplug and remove the EGR Valve Vacuum Solenoid. Take the cap off and clean it out. blow a little air thru it. Not to much pressure. A computer air can will work. Reasemble and see if that changes anything.

As I said it worked for me after changing the DPFE and following the steps in the link I posted before.

Also maybe disconnect the neg and positive cables over night just to be sure it clears everything. Reconnect the cables in the morning and see what happens.

I can try that. I did clean it out when I pulled it to check it.

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