P0420 is a catalytic converter low efficiency code. Has nothing to do with your crank sensor. I've heard of people changing oxygen sensors and it going away, but its likely if it comes back you need a new cat.
Crankshaft position sensor 2002 Buick Lesabre P0420
Over the past year I would get a one time intermittent stop (engine would stop for a fraction of a second then resume when going at highway speeds)when traveling over 20 miles on my 3.8L engine. At first there were no DTC's or start up stalls after the engine warmed up. My fuel pressure was good so I suspected ignition. Several months ago the momentary engine stop produced a P0420. Finally a month ago my engine refused to start until I waited for 40 minutes start it after it stopped. Since this was a likely symptom of a crankshaft position sensor and it was 120K (12 years) since it was changed, I installed a new one. I then deleted the engine trouble code P0420 and in 200 miles it has not come back. I noticed a mechanic on the OReillyauto parts site said he had a P0420 that went away after installing a crankshaft position sensor on a 3.8L and had never seen anything like that in his 30 years of service. Has anyone else had this experience or do you think this is just an anomally? Would appreciate some feedback.
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So what do you theorize is the reason my P0420 code, the only code that showed after the brief stalls (maybe a whole second) during highway speeds), went away after I changed the crankshaft position sensor? I have about 200 miles after the new install and no codes.P0420 is a catalytic converter low efficiency code. Has nothing to do with your crank sensor. I've heard of people changing oxygen sensors and it going away, but its likely if it comes back you need a new cat.
If the car's angry about the air-fuel readings across the O2 sensor just enough to occasionally throw that code, running rough could be what caused it. The sensors don't directly read from specific components in every spot on the engine, just resulting effects of how the engine is operating. This is why each vehicle builds up common troubleshooting history with various codes and conditions, since they are saying different things with how they're programmed to alert you for different readings.
You can also blow up engines without ever seeing a code, because conditions that trigger them may not come up until it's too late. With these cars/engines reaching 25+yrs old, using electronics and components that are wearing out in new ways, it takes a bit more technique and patience to troubleshoot some things that happen in their aging systems.
You can also blow up engines without ever seeing a code, because conditions that trigger them may not come up until it's too late. With these cars/engines reaching 25+yrs old, using electronics and components that are wearing out in new ways, it takes a bit more technique and patience to troubleshoot some things that happen in their aging systems.
Exhaust leaks? P0420 can be a bear to diagnose. Anything from worn out spark plugs to low fuel pressure can throw enough sensors off that a P0420 can come up. After replacing the crank sensor, did the stalling concern go away?So what do you theorize is the reason my P0420 code, the only code that showed after the brief stalls (maybe a whole second) during highway speeds), went away after I changed the crankshaft position sensor? I have about 200 miles after the new install and no codes.
Completely gone. My Idle LTFT is .8 and my LTFT at >2000 RPM is about -6. I changed the lower intake manifold about 4K miles ago (230K) with iridium plugs. Now it runs great.Exhaust leaks? P0420 can be a bear to diagnose. Anything from worn out spark plugs to low fuel pressure can throw enough sensors off that a P0420 can come up. After replacing the crank sensor, did the stalling concern go away?
Could have been an aberration. If it hasn't come back, keep on trucking man!Completely gone. My Idle LTFT is .8 and my LTFT at >2000 RPM is about -6. I changed the lower intake manifold about 4K miles ago (230K) with iridium plugs. Now it runs great.
I just wondered if the logic of my car's computer saw the transitory stall at highway speeds if instead of posting a P0300 it just saw a whish of unburned gas and decided the cat converter was bad registering a P0420. I only have seen one other person say they had this happen with their 3.8L. Since you've worked on a number of these engines it sounds like you have never seen this particular code associated with the crankshaft position sensor but you are not terribly surprised it posted. Would that be a fair summary.If the car's angry about the air-fuel readings across the O2 sensor just enough to occasionally throw that code, running rough could be what caused it. The sensors don't directly read from specific components in every spot on the engine, just resulting effects of how the engine is operating. This is why each vehicle builds up common troubleshooting history with various codes and conditions, since they are saying different things with how they're programmed to alert you for different readings.
You can also blow up engines without ever seeing a code, because conditions that trigger them may not come up until it's too late. With these cars/engines reaching 25+yrs old, using electronics and components that are wearing out in new ways, it takes a bit more technique and patience to troubleshoot some things that happen in their aging systems.
This crank sensor seemed to die a very slow death. You know how you decelerate to a stop. It seemed not quite as usual but it never stalled or had a lack of power when you stepped on the gas. Eric of South Main Auto on Youtube called some of these symptoms a "fish bite" where the sensor (in his case an O2 sensor) is worn enough to not quite keep up with it's monitoring duties and culminates in an intermittent stall for a second. To me a P0300 would have been more logical if the POP335 wasn't initiated. Anyway thanks for the good will. Have a good day!Could have been an aberration. If it hasn't come back, keep on trucking man!
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