Replacing the downstream O2 sensors will NEVER fix a 420/430. Failed sensors will store other codes. Possible the upstream sensor is lazy or contaminated causing chemical shift, but the most likely cause is a failing cat. If the cat isnt broken up and causing excessive back pressure, the easy fix are some "MIL Eliminators" sold by many online stores including Amazon and Ebay for around $20 a pair. Simply remove the downstream sensor, screw in the device, and screw the sensor into the device. They work.
P0430 - "CAT Efficiency Below Threshold, Bank 2"
I've got that error, and had it for a while already. I've had it on my other vehicles before as well, and the fix has always been to replace the downstream o2 sensors. Well, I did that a few weeks ago on my Taurus and changed both downstream o2 sensors (replaced with Motorcraft units) even though only one was bad. Why, you ask? Because my train of thought is to "replace it in pairs". Since getting to the rear o2 sensor's pig-tail harness was quite an adventure which required removal of the upper intake manifold, I decided to replace all 6 spark plugs (replaced with Motorcraft platinums) as well because removing the intake manifold is part of the same job to replace the spark plugs. I wrap everything back up, clear the code, and go on for a 65 mile drive, ~50mi on highway, and ~15mi on surface streets. The code stays off and I'm a happy camper. This was about 3 weeks ago.
Fast forward to just this past Tuesday and I get another CEL. I get out my ODB-II scanner, and I'm surprised to get the P0430 code again.
Reading online what some people have experienced when getting this code, symptoms vary from nothing noticeable aside from the CEL being on, loss of fuel efficiency, to misfires, and very sluggish performance. My experiences seem to be just the CEL being on. Some people have said they've needed to replace their CAT while other's have just needed to replace the o2 sensors. And here's where my confusion is. Some people replaced the pre-CAT o2 sensors and others have replaced the downstream o2 sensors (like I did). Some people replaced the CAT all together.
What troubleshooting do I need to do to figure out what it is that I need to fix? Some have suggested to swap the o2 sensors around. Some have said to replace the upstream sensors. Those are good ideas which I could try, but what else is there for me to try?
Fast forward to just this past Tuesday and I get another CEL. I get out my ODB-II scanner, and I'm surprised to get the P0430 code again.
Reading online what some people have experienced when getting this code, symptoms vary from nothing noticeable aside from the CEL being on, loss of fuel efficiency, to misfires, and very sluggish performance. My experiences seem to be just the CEL being on. Some people have said they've needed to replace their CAT while other's have just needed to replace the o2 sensors. And here's where my confusion is. Some people replaced the pre-CAT o2 sensors and others have replaced the downstream o2 sensors (like I did). Some people replaced the CAT all together.
What troubleshooting do I need to do to figure out what it is that I need to fix? Some have suggested to swap the o2 sensors around. Some have said to replace the upstream sensors. Those are good ideas which I could try, but what else is there for me to try?
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ALL narrow band O2 sensors operate by the same chemistry. the only difference between any O2 sensors is the electrical connector and the length of the wires. Any brand is fine.... Bosch (who first produced them back in the 1970s), Denso, NGK, NTK, etc. If I remember correctly Morotcraft are rebadged NGK.
As I stated earlier in this thread, replacing the post cat sensors will NEVER cure a 430/420. Failed post cat sensors will set a DIFFERENT code. Post cat sensors often last the life of the car.
Example: A year ago my adult daughters 85K mile 13 Limited threw a 420. She has an extended warranty. She took it to the Ford dealer. Some moron who should never be allowed to open the hood of a car replaced the bank 1 post cat O2. I told her the CEL would come on in a day or 2. She stated that the dealer said the car was fixed. Guess who was right. Hint: I was not the dealer. The dealer ended up replacing the bank 1 cat with no deductable after I told the service manager that the tech who diagnosed the problem as a bad sensor didnt have a clue.
The "MIL Eliminators" will keep the CEL off allow you to pass smog. If the car is visually inspected on a lift, an astute inspector may notice the eliminators. Years ago when we had visual inspections along with a tailpipe sniffer test here in SE WI, and the inspectors didnt know an EGR valve from a fuel injector, and passed everything unless you pulled in with a 8-71 Roots blower sticking up 2 feet out of your hood.
Example: A year ago my adult daughters 85K mile 13 Limited threw a 420. She has an extended warranty. She took it to the Ford dealer. Some moron who should never be allowed to open the hood of a car replaced the bank 1 post cat O2. I told her the CEL would come on in a day or 2. She stated that the dealer said the car was fixed. Guess who was right. Hint: I was not the dealer. The dealer ended up replacing the bank 1 cat with no deductable after I told the service manager that the tech who diagnosed the problem as a bad sensor didnt have a clue.
The "MIL Eliminators" will keep the CEL off allow you to pass smog. If the car is visually inspected on a lift, an astute inspector may notice the eliminators. Years ago when we had visual inspections along with a tailpipe sniffer test here in SE WI, and the inspectors didnt know an EGR valve from a fuel injector, and passed everything unless you pulled in with a 8-71 Roots blower sticking up 2 feet out of your hood.
1 - 5 of 31 Posts
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