Hey guys I have had this code for about 2 months now, and my gas mileage is getting really poopy. Im gonna replace both cats on my 05 5.4. Looking at Magnaflow Want to get some that will get rid of the check engine light without a tune. Right now my setup is all stock except for the flowmaster 40 series muffler SI/DO....Can you guys tell me what you run and how you like them? Also a part number and price would be great if you can.

 

You may have to look at more than the cat for being the cause of the code.......
See link.....http://www.obd-codes.com/p0420

Also if you have a 2005 5.4 3v you may want to investigate a faulty injector also.....

See link....https://www.f150online.com/forums/v8...ram-07m08.html

 

Might kill two birds with one stone at the dealership. Cat's fall under the emissions warranty , that's up to 100,000 miles. You may receive new injectors as well, if your under in mileage. Both have warranties, injectors= extended warranty.

Might be a free visit and your truck coming home with new parts.

 

And don't think that putting in Magnaflow cats is a cure all. Mine have been in for a year and they just started throwing the same code as you. Funny thing is that I never had this problem until I had some touch up welding for some leaking done to them when I was getting my true duals installed.

 

I've been getting the same code the last few weeks, along with P0430 (other bank). Not sure why they started all of the sudden, but I haven't noticed any gas mileage drops. Everything seems fine to me. The exhaust guy told me it would likely throw a code when I got my exhaust upgraded, but it was fine (until now).

 

I put them in order if you want to check yourself. Service does the same. -


HF7 CHECK FOR OBVIOUS LEAK SOURCES IN THE EXHAUST SYSTEM

Note: If a catalyst is in series with a leaking exhaust system, it can fail the Catalyst Efficiency Monitor test.

Inspect the following for leaks, cracks, loose connections or punctures:

Exhaust manifold.
Front exhaust pipe.
Rear exhaust pipe.
Muffler/tailpipe assembly.

Are the above components free of cracks and punctures,etc.?

__________________________________________________ ___________

HF5 CHECK REAR HO2S WIRING AND PCM CONNECTIONS

Note: If the electrical connections of the rear HO2S are interchanged/crossed, the Catalyst Efficiency Monitor Test will fail.

Inspect the wiring of each rear HO2S for proper routing and connection.
Disconnect the PCM, inspect for damaged or pushed out pins, corrosion and loose wires.

Are there any concerns with the HO2S wiring or the PCM connection?

__________________________________________________ ____________

 

Note for the above: No other DTC's present, just for DTC's 420/430 alone

 

Hey just an update...I got my plugs changed at the dealer last Thursday, and they cleared the code for me...The CEL has not came back on since....Last time I cleared the code with my gryphon and it was back on within 2 days. Now I did put my factory intake back on the night before I took it to the dealer, so that may be it, but I drove it about 30 miles with the stock intake back on it and the light stayed on. Could the plugs have caused this code?

 

The light won't go off unless reset,erase the KAM. Yea, -Intake and plugs have nothing to do with the 420/430 set. And your O2's are working as they should. My other post above has some direction for ya, - where to look.

Might be the tune, not sure. Where you running a tune at the time, when you had your first 420 or 430 DTC ? Did you return to stock before the dealer ?

It's usually either an exhaust/exhaust manifold leak, cracked converter under the heat shield. You can't always see it, but they can crack across the bottom (from right to left). It could be a bad cat.

 

Yeah I had a 87 perf tune from php when the light came on... I returned it to stock and reset the light and it came back on after a couple of days....Now the truck is completely stock and just had the plugs changed....it took a while longer but the light came back on yesterday. Im putting magnaflow 94136 cats on tomorrow. I will update later. Hopefully these new high flows will fix the problem as well as improve the sound of my exhaust.

 

Heres's what's goin on, in short. PCM Program: - The switch rate of the rear sensors are compared to the switch on the front. If the catalyst is efficient it will be removing HC and HO and the rear sensor will show a slow switch rate compared with the front. By dividing the number of downstream switches with those of the upstream gives a catalyst switch ratio, and a typical threshold is 75%, above which a DTC will be recorded.

It take a little while after reset because this test must be failed three times before the MIL (CEL) light is switched on.

Another thing, in case you don't know,-faulty HO2S sensors do not produce the DTCs P0420 and P0430. The sensors must all be tested and shown to be reliable before the Catalyst Monitor can be called by the Executive (run).

So yea, 420/430 point right to the cats. There's other DTC's that point to the sensor, but you don't have them. There's also other DTC's that point to the harness, - you don't have those either.

So , a leak before the converter will force to much HO. A bad cat will force DTC.

You thought it may have been the plugs. That's nearly impossible because the Monitor Sequence program has to complete these tests before the Catalyst Monitor can run. It's called conditions or conditions met. - If I can remember -

1. HO2S monitor tests complete and no DTCs
2. You can't have any Fuel Trim DTCs
3. EGR Monitor Complete
4. No Misfire DTCs (which IS ignition of course)

I know I forgot one lol, shoot maybe two iduno...

 

if ya gotta get new ones might as well upgrade (well thats my excuse to buy new stuff) you wont regret the magnaflow highflows i got mine off preformance peddler for just under 100 bucks for both. they filter completely and dont throw codes. and i had the same muffler you had at one point, i dont know how you feel but i'd probaly think it could use a little help from some good cats

 

The 94136 did the trick...The light is now gone, and my exhaust sounds friggin beastly....I love them.

 

How many miles on the truck/new exhaust Matt? Doubt its new O2 time. Try gonig back to stock tune for a day and re-uploading custom?

 

Good deal

Yea, I like the way they sound as well. I welded mine to the collectors on the headers. Nice deep sound.