• Welcome Visitor! Please take a few seconds and Register for our forum. Even if you don't want to post, you can still 'Like' and react to posts.

Intermittent P0420 code


Vindictus

Well-Known Member
Joined
Sep 4, 2011
Messages
262
Reaction score
281
Points
63
Location
NewBrunswick Canada
Vehicle Year
2011
Make / Model
Ford Ranger
Engine Type
4.0 V6
Engine Size
ReMan 4.0 SOHC
Transmission
Manual
2WD / 4WD
2WD
Tire Size
235/75/15
This started Monday night. Out to the store and CEL came on. I rest it, went to work Tuesday (60 miles) all was good. Went out after work it came on again. reset it and came on, on my way home to night. I replaced both cat's and O2 censors about 3 years ago. O2's are motorcraft cat's are from Eastern Catalytic. Shouldn't they last longer?? Could anything else besides a bad cat cause this? Like an exhaust leak of some kind? Thanks everyone
 


Craig0320

Well-Known Member
Supporting Member
Article Contributor
V8 Engine Swap
TRS 20th Anniversary
Joined
Sep 21, 2017
Messages
1,207
Reaction score
219
Points
63
Location
Mississppi
Vehicle Year
1998
Make / Model
Ford
Engine Type
V8
Engine Size
5.0
Transmission
Automatic
2WD / 4WD
4WD
My credo
Break it right the first time. Fix it better the next time.
Check your rear o2 sensors on a scanner and they should be mostly solid non moving if you have a good functioning set of cats. In park at operating temperature have the engine at a constant 2000 rpms. Using a digital thermometer take the inlet cat temp and the exit cat temp. The temperature should be hotter coming out the back by at least 200 degrees even a little less won't through a code. This lets you know the cat is doing what it's supposed too.
 

Vindictus

Well-Known Member
Joined
Sep 4, 2011
Messages
262
Reaction score
281
Points
63
Location
NewBrunswick Canada
Vehicle Year
2011
Make / Model
Ford Ranger
Engine Type
4.0 V6
Engine Size
ReMan 4.0 SOHC
Transmission
Manual
2WD / 4WD
2WD
Tire Size
235/75/15
Check your rear o2 sensors on a scanner and they should be mostly solid non moving if you have a good functioning set of cats. In park at operating temperature have the engine at a constant 2000 rpms. Using a digital thermometer take the inlet cat temp and the exit cat temp. The temperature should be hotter coming out the back by at least 200 degrees even a little less won't through a code. This lets you know the cat is doing what it's supposed too.
I did check them with my scanner and they are not moving very much. My scanner is showing both cat's almost identical temp's. I'll bring a temp gun home from work and check this weekend. Thanks for the help
 

Vindictus

Well-Known Member
Joined
Sep 4, 2011
Messages
262
Reaction score
281
Points
63
Location
NewBrunswick Canada
Vehicle Year
2011
Make / Model
Ford Ranger
Engine Type
4.0 V6
Engine Size
ReMan 4.0 SOHC
Transmission
Manual
2WD / 4WD
2WD
Tire Size
235/75/15

Vindictus

Well-Known Member
Joined
Sep 4, 2011
Messages
262
Reaction score
281
Points
63
Location
NewBrunswick Canada
Vehicle Year
2011
Make / Model
Ford Ranger
Engine Type
4.0 V6
Engine Size
ReMan 4.0 SOHC
Transmission
Manual
2WD / 4WD
2WD
Tire Size
235/75/15
I had a chance to look at this p0420 code some more. Code reader list these as possible causes.
Incorrect fuel grade used
fault Bank 1 Sensor 1 Oxygen sensor
Fault Bank 1 Sensor 2 Oxygen sensor
Faulty Engine Coolant Temperature (ECT) sensor
Damaged or Leaking exhaust system
Excessively retarded spark timing

Why can't it be easy o_O
 

Vindictus

Well-Known Member
Joined
Sep 4, 2011
Messages
262
Reaction score
281
Points
63
Location
NewBrunswick Canada
Vehicle Year
2011
Make / Model
Ford Ranger
Engine Type
4.0 V6
Engine Size
ReMan 4.0 SOHC
Transmission
Manual
2WD / 4WD
2WD
Tire Size
235/75/15
Changed O2 sensors and CEL still throws 420 code. I will check inlet and outlet temps of cat when i get to work in the morning
 

Vindictus

Well-Known Member
Joined
Sep 4, 2011
Messages
262
Reaction score
281
Points
63
Location
NewBrunswick Canada
Vehicle Year
2011
Make / Model
Ford Ranger
Engine Type
4.0 V6
Engine Size
ReMan 4.0 SOHC
Transmission
Manual
2WD / 4WD
2WD
Tire Size
235/75/15
Check your rear o2 sensors on a scanner and they should be mostly solid non moving if you have a good functioning set of cats. In park at operating temperature have the engine at a constant 2000 rpms. Using a digital thermometer take the inlet cat temp and the exit cat temp. The temperature should be hotter coming out the back by at least 200 degrees even a little less won't through a code. This lets you know the cat is doing what it's supposed too.
I checked my cat's temp's this morning. The inlet temp is 445F the outlet temp is 285F with a difference of 160F so looks like I need a new cat :( I wonder if it's worth doing warranty through rockauto?
 

Craig0320

Well-Known Member
Supporting Member
Article Contributor
V8 Engine Swap
TRS 20th Anniversary
Joined
Sep 21, 2017
Messages
1,207
Reaction score
219
Points
63
Location
Mississppi
Vehicle Year
1998
Make / Model
Ford
Engine Type
V8
Engine Size
5.0
Transmission
Automatic
2WD / 4WD
4WD
My credo
Break it right the first time. Fix it better the next time.
I would reach out to them first. That is definitely not doing it's job effectively.
 

19Walt93

Well-Known Member
Ford Technician
V8 Engine Swap
Joined
Nov 13, 2018
Messages
3,962
Reaction score
3,423
Points
113
Location
Canaan,NH
Vehicle Year
1993
Make / Model
Ford Ranger
Engine Type
V8
Engine Size
351
Transmission
Automatic
2WD / 4WD
2WD
Total Drop
3"
Tire Size
235/55R16
My credo
If you don't have time to do it right will you have time to do it over?
First, the "rear O2", isn't an oxygen sensor, it's called a cat monitor. Ask an experienced Ford counterman for a rear O2 and he'll look at you like you're an idiot. I agree with trying the cheap stuff first but I have never seen a PO420 fixed by replacing anything but a cat. We replaced darn few, almost exclusively with OEM parts or Walker direct fit cats if the customer gasped at the OEM price.
 

Sponsored Ad


Sponsored Ad

Members online

Today's birthdays

Member & Vendor Upgrades

For a small yearly donation, you can support this forum and receive a 'Supporting Member' banner, or become a 'Supporting Vendor' and promote your products here. Click the banner to find out how.

Recently Featured

Want to see your truck here? Share your photos and details in the forum.

Follow TRS On Instagram

Carlisle Truck Nationals

Join us at the Carlisle Truck Nationals for the 40th Anniversary of the Ford Ranger.

Check Out The TRS Store


Sponsored Ad


Sponsored Ad

Sponsored Ad


Amazon Deals

Top