Managment light came on the other day with fault code p0420 catalyst system efficiency below threshold bank 1, the car has within the last 12 months had the cat done what are the other common problems that cause this fault code? Would it be the first sensor in the exhaust system in the down pipe before the cat?
s1john
hi, found this on ford wiki hope it helps :
P0420
Error Description
Catalyst System Efficiency Below Threshold (Bank 1) Indicates Bank 1 catalyst system efficiency is below the acceptable threshold Use of leaded fuel Damaged HO2S Malfunctioning ECT High fuel pressure Damaged exhaust manifold Damaged catalytic converter Oil contamination Cylinder misfiring Downstream HO2S wires improperly connected Damaged exhaust system pipe Damaged muffler/tailpipe assembly Retarded spark timing Compare HO2S upstream and downstream switch rate and amplitude. Under normal closed loop fuel conditions, high efficiency catalysts have oxygen storage which makes the switching frequency of the downstream HO2S very slow and reduces the amplitude of those switches as compared to the upstream HO2S. As catalyst efficiency deteriorates, its ability to store oxygen declines and the downstream HO2S signal begins to switch more rapidly with increase amplitude, approaching the switching rate and amplitude of the upstream HO2S. Once beyond an acceptable limit the DTC is set.
P0420
Error Description
Catalyst System Efficiency Below Threshold (Bank 1) Indicates Bank 1 catalyst system efficiency is below the acceptable threshold Use of leaded fuel Damaged HO2S Malfunctioning ECT High fuel pressure Damaged exhaust manifold Damaged catalytic converter Oil contamination Cylinder misfiring Downstream HO2S wires improperly connected Damaged exhaust system pipe Damaged muffler/tailpipe assembly Retarded spark timing Compare HO2S upstream and downstream switch rate and amplitude. Under normal closed loop fuel conditions, high efficiency catalysts have oxygen storage which makes the switching frequency of the downstream HO2S very slow and reduces the amplitude of those switches as compared to the upstream HO2S. As catalyst efficiency deteriorates, its ability to store oxygen declines and the downstream HO2S signal begins to switch more rapidly with increase amplitude, approaching the switching rate and amplitude of the upstream HO2S. Once beyond an acceptable limit the DTC is set.
The first sensor(in the downpipe) is for the ECU. It measures the richness of the exhaust gases and relays this back to the ECU which then adjusts your mixture to ensure correct running.
The second sensor(after the cat) is the one reporting your error. It measures the gases coming out of the cat and is solely used to determine the efficiency of the cat. It's possible that you may have a problem somewhere else but, most likely, you have a problem with the cat or, the sensor itself.
Personally, I would try getting this sensor replaced as a first step assuming that, the car is running fine otherwise ?
Mart.
The second sensor(after the cat) is the one reporting your error. It measures the gases coming out of the cat and is solely used to determine the efficiency of the cat. It's possible that you may have a problem somewhere else but, most likely, you have a problem with the cat or, the sensor itself.
Personally, I would try getting this sensor replaced as a first step assuming that, the car is running fine otherwise ?
Mart.
Yes seems to be running fine, feels a bit sluggish to me but then I am used to driving a modified st24 rather than a 2.0 estate. Cheers for the replies I think I have a sensor in monst my parts
A P0420 can be caused by a lot of things. As Mart said, the front and rear o2 readings are compared by the ecu. The front is used for fuel control and the rear is a catalyst monitor. Due to the way cats store oxygen the rear o2 reading should remain relatively steady, and only change significantly on full throttle, then again when letting off.
Things I've seen cause the code include using leaded petrol when the car should be run on unleaded (like all catalyst cars should), a car burning excessive oil and contaminating the cat, leaking fuel injectors causing the cat to start to melt, an exhaust leak either at the front o2 or near the rear o2, causing the readings to become similar to each other (though a leak near a front 02 usually results in a P0171 Bank 1 lean code also being set) and on older cars, the coolant temp sensor. The temp sensor causes this issue because it's used to tell the ecu when the car is warm enough to be able to trust the front o2 sensor. This is less likely on newer cars (last 15 years or so) as they have heated oxygen sensors that come up to temp in a matter of 30 seconds or so.
Before you try replacing the rear o2, get a scan tool with live data and see what's going on. If the rear o2 is switching in time with the front then I'd suspect the cat is bad.
Also note that while catalysts do go bad, quite often there is an underlying cause (as mentioned above). Replacing the catalyst and not taking care of the problem causing it to fail (if there is a problem ) will just kill the new catalyst too.
Posted Via The Free TalkFord.com App
Things I've seen cause the code include using leaded petrol when the car should be run on unleaded (like all catalyst cars should), a car burning excessive oil and contaminating the cat, leaking fuel injectors causing the cat to start to melt, an exhaust leak either at the front o2 or near the rear o2, causing the readings to become similar to each other (though a leak near a front 02 usually results in a P0171 Bank 1 lean code also being set) and on older cars, the coolant temp sensor. The temp sensor causes this issue because it's used to tell the ecu when the car is warm enough to be able to trust the front o2 sensor. This is less likely on newer cars (last 15 years or so) as they have heated oxygen sensors that come up to temp in a matter of 30 seconds or so.
Before you try replacing the rear o2, get a scan tool with live data and see what's going on. If the rear o2 is switching in time with the front then I'd suspect the cat is bad.
Also note that while catalysts do go bad, quite often there is an underlying cause (as mentioned above). Replacing the catalyst and not taking care of the problem causing it to fail (if there is a problem ) will just kill the new catalyst too.
Posted Via The Free TalkFord.com App
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
