P0420 & P0430 Codes
#1
#2
Gus:
That's a general o2 control fault. You imply it came up on both banks at nearly the same time, so I would bet it is not sensor or cat related. That leaves a MAF problem (have you cleaned it lately?) or an air leak in the induction plenum. The manual says exhaust leaks are another source, and cracked exhaust manifolds causing O2 havoc is also a known problem on these cars.
That's a general o2 control fault. You imply it came up on both banks at nearly the same time, so I would bet it is not sensor or cat related. That leaves a MAF problem (have you cleaned it lately?) or an air leak in the induction plenum. The manual says exhaust leaks are another source, and cracked exhaust manifolds causing O2 havoc is also a known problem on these cars.
#3
#4
#5
#6
These codes are catalyst effeciency codes, not general O2 sensor codes.
P0420-catalyst effeciency below threshold bank 1
P0430-catalyst effeciency below threshold bank 2
Bank 1 is Cyls. 1-3
Bank 2 is Cyls. 4-6
Although exhaust manifold cracks are common on these cars, these codes are most certainly caused by your catalytic converter which is bolted to the exhaust manifolds. If you hook up a datastream tool of some sort and monitor the downstream 02 sensors when the engine is nice and toasty, you will notice they are probably swinging from about 0v to 1v. This should NOT be happening. They should read approx. .5 volts when idling and should not fluctuate. If the 02 sensors are fluctuating, the catalyst material is compromised and not doing it's job......cleaning up exhaust gasses. I take it this vehicle has high miles, say above 60 or 70k? If so, replace the cat. We do them frequently. If you don't replace the cat, and decide to clear the codes, they will most certainly return with a quickness.
P0420-catalyst effeciency below threshold bank 1
P0430-catalyst effeciency below threshold bank 2
Bank 1 is Cyls. 1-3
Bank 2 is Cyls. 4-6
Although exhaust manifold cracks are common on these cars, these codes are most certainly caused by your catalytic converter which is bolted to the exhaust manifolds. If you hook up a datastream tool of some sort and monitor the downstream 02 sensors when the engine is nice and toasty, you will notice they are probably swinging from about 0v to 1v. This should NOT be happening. They should read approx. .5 volts when idling and should not fluctuate. If the 02 sensors are fluctuating, the catalyst material is compromised and not doing it's job......cleaning up exhaust gasses. I take it this vehicle has high miles, say above 60 or 70k? If so, replace the cat. We do them frequently. If you don't replace the cat, and decide to clear the codes, they will most certainly return with a quickness.
Last edited by poboyblues; 07-13-2009 at 11:37 PM.
#7
poboyblues"
Unless ther ehas been a contamination event, it is highly unlikely that two cats will go out on these cars at the same time. And my cats, as well as many other's have gone for more than 200,000 miles. The code means the front lambdas do not match the back, which can come from bad cats, or from bad sensiors, or from a leak, or from being outside the operating range. And that is all in the shop manual, and makes good sense. I stand by my advice on this.
Unless ther ehas been a contamination event, it is highly unlikely that two cats will go out on these cars at the same time. And my cats, as well as many other's have gone for more than 200,000 miles. The code means the front lambdas do not match the back, which can come from bad cats, or from bad sensiors, or from a leak, or from being outside the operating range. And that is all in the shop manual, and makes good sense. I stand by my advice on this.
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#8
"If you hook up a datastream tool of some sort and monitor the downstream 02 sensors when the engine is nice and toasty, you will notice they are probably swinging from about 0v to 1v. This should NOT be happening. They should read approx. .5 volts when idling and should not fluctuate"
This is absolutely wrong!! The transition time, not the absolute value is the controlling constant. If the sensors are not cycling (either upstream or downstream) then something is wrong.
This is absolutely wrong!! The transition time, not the absolute value is the controlling constant. If the sensors are not cycling (either upstream or downstream) then something is wrong.
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#11
My S-type Jag 2003
I have an interesting situation. My check engine light comes on after getting gas, so I changed the gas cap and it is still on. It goes off after the tank goes below 3/4 or 1/2 with no consistency. Recently my car had a gunked up Mass Air Flow Sensor causing the car to stop in the AZ Desert. The code is P0420, but one cat has been replaced already. Any clues?
#12
So a P 0420 code bank 1 below specification - would it be the front O2 sensor that would be a good bet to replace ? I see one O2 sensor on each section of the exhaust manifold
these front o2 sensors seam to be the most common part available so I'm guessing it a common issue... Bank one I'm assuming would be the sensor closes to front of the car ( corresponding to the first three cylinders )
I forgot - my car is 1995 xjs 4.0 -
these front o2 sensors seam to be the most common part available so I'm guessing it a common issue... Bank one I'm assuming would be the sensor closes to front of the car ( corresponding to the first three cylinders )
I forgot - my car is 1995 xjs 4.0 -
#13
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philwarner
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