Hello all, first time posting, but need some help.


I have a 1996 F150 4.6L manual that was giving me a P0443 code. I replaced the Purge valve and reset the codes. I drove it for over 200 miles and it was not ready for emissions testing. I foud the drive cycle requirements and completed two cycles. at the end of the second drive cycle the engine light came back on. I checked the codes and had a P0443 and P0402. Once I started the engine again the codes had cleared, but the system is not ready for emission inspection again with 5 devices not ready.


Please help, I am at wits end.


Thanks

 

You are on the right track. Those codes point to the EVAP purge solenoid and/or it's wiring. Get your EVTM out and start troubleshooting.

The info you are sharing is not correct. Either the year, (1996), or the engine, (4.6l) is incorrect, or there is an engine swap that you are not telling us about. No 1996 built with a 4.6.

 

A 1996 truck w/OBD-II should have a Vapor Management Valve


Not the older style CANP valve


I have seen that P0443 error code pop up several times on different forums. It's usually resolved by replacing the computer (PCM).

 

Thanks, I have replaced the Purge valve and reset the codes. When I do the drive cycle code P0443 will come on with P0402 (I just bought the DPFE valve). When I turn the truck off and start it again the codes go away, just not ready for emission testing.


I hope it is not the computer.




Yea, it a 4.9L not 4.6L.

 

A failed computer will be the last thing to check on your list. Others will disagree, but I'm right! If it runs, safest bet is that the computer is OK. It is doing it's job by telling you something is wrong with the inputs to the computer. Some will say capacitors inside the ECM fail and cause this. Entirely possible, but it will be accompanied by other mysterious failures. Capacitor replacement is not difficult and is cheap insurance. There are many threads on this in this forum.

Check the circuit from the purge valve to the ECM. This means checking the connectors and continuity between the associated pins. This is where you need the correct EVTM for your vehicle. Sorry, but I don't have one for your truck. I'm sure someone will have one and may post, otherwise search is your friend.

 

Normally I would agree with you, but I have gone through this before. Anything is possible, Verify the VMV is electrically connected and getting power.

 

Yes it is!

As the electronic components age, an ECM failure does become more likely. Let's face it, a 20 year old electrolytic capacitor will be unreliable. Other components will not wear out under normal use for many lifetimes.

If another known good ECM is available, it is an easy check to swap it out. If not, it can be an expensive component to locate and a big disappointment when it does not fix the problem.

I still would rather diagnose than throw parts at the problem, but I can agree with your experience.

 

So I have replaced the purge valve (VMV) and the DPFE EGR and I now have a code of p0443 with codes of P0402 and P0420 pending.


When I let the truck sit the codes clear but the truck shows not ready for inspection. Once I put it through a drive cycle, the codes come back.


Could it be a battery problem? I read somewhere that it may cause the monitors not reset.


thanks again for the help.

 

Did you replace the silicone hoses that run from the EGR tube sample tubes and the DPFE? Those things get brittle with age. (P0402).

P04443 code remains...and now you have a new one popping up P0420.

If the battery is charged and starts the truck without much effort, then I seriously doubt you have a battery problem. If the truck does have issues starting or the battery runs down quickly then you have a likely culprit for why you cannot get the Monitors in proper state.

Just like the OBD-I counterparts, you may be suffering from leaking capacitors just like the older computers (PCM).