0420 code?
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From: Central Ohio
0420 code?
I have a 99 F150 4x4 with the 4.6l. The SES light came on and I went to Autozone to have it checked. It read 0420 catlyst below threshold bank #1? I have no idea what this means and the kid at Autozone had little to offer. The simptoms are the engine idles fine, runs rough under acceleration until fully warmed up, and gas mileage has gone to hell. Any ideas?
Thanks in advance.
jj
Thanks in advance.
jj
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Joined: Oct 2002
Posts: 7,295
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From: St. Louis (Out in the woods)
I suspect your rough running and poor fuel mileage concerns are likely due to a fault in the secondary ignition system. Plugs, coils, etc all come to mind. What is the mileage and has it ever had a tuneup?
The P0420 means the cat is no longer doing its job as measured by the onboard computer. If you have it, review your Emissions Warranty booklet to see what the coverage is on the cats. I do not know if the light trucks have to follow the same terms as do passenger cars, but my 98 Contour was covered by the federal 8/80 warranty and got a new set of cats last summer under the warranty (at 78K miles).
Steve
The P0420 means the cat is no longer doing its job as measured by the onboard computer. If you have it, review your Emissions Warranty booklet to see what the coverage is on the cats. I do not know if the light trucks have to follow the same terms as do passenger cars, but my 98 Contour was covered by the federal 8/80 warranty and got a new set of cats last summer under the warranty (at 78K miles).
Steve
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From: Central Ohio
Steve thanks for the reply, The truck has 104,000 miles on it. The plugs and wires were replaced at 92,000 miles. Everything was running fine until last week, and it has been running rough ever since. If it were wires or plugs would there not be other codes showing up? Could a Oxygen sensor possibly be the culprit?
jj
jj
Last edited by j jennings; Mar 21, 2004 at 09:57 PM.
Senior Member
Joined: Oct 2002
Posts: 7,295
Likes: 125
From: St. Louis (Out in the woods)
If your 99 4.6 has COPs (I don't know when they went to COP on the 4.6), the PCM is fairly likely to pick up a misfire due to spark issues.
If you have standard plug wires, the odds are much less that a misfire would be picked up by the computer.
Do you recall what brand of plugs and wires were used? Some brands have demonstrated good reliability, others not so good.
If it were an oxygen sensor, the computer would be expected to have self-diagnosed that.
Steve
If you have standard plug wires, the odds are much less that a misfire would be picked up by the computer.
Do you recall what brand of plugs and wires were used? Some brands have demonstrated good reliability, others not so good.
If it were an oxygen sensor, the computer would be expected to have self-diagnosed that.
Steve
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From: Central Ohio
I'm not sure if this is a COP 4.6, but when I replaced the ignition wires I was getting a misfire code. I do not remember the exact code. I used what ever Autozone has for their standard replacement wires. The plugs were changed at the dealership.