kponhlo
Member
- Joined
- August 1, 2003
- Messages
- 26
- Reaction score
- 0
- City, State
- Niskayuna, NY
- Year, Model & Trim Level
- '97 XLT
Hi. I have a '97 4.0L SOHC, 102k, XLT, that has set code P0420 only. I replaced the leaking intake gaskets a few months ago, but the code P0420 waited a few weeks before appearing. The truck also has a rough idle. I have cleared the codes and it comes back the same. i also hooked up a scan tool to view the O2 sensor data - all four of the sensors read 0.00 mV AND the fuel trims are at 100-percent.
From reviewing other posts here, it seems that a P0420 is probably the post-cat O2 sensor on bank 1, but could also be the cat itself. It also seems that the rough idle could be caused by an O2 sensor (or sensors) that have failed or it could simply need a good fuel system cleaning, although I do run good fuel additives on a fairly regular basis. I replaced one of the pre-cat O2 sensors when the truck had about 60k, but the others I suspect are original.
I am wondering why none of the O2 sensors are reading a voltage, and why the fuel trims appear to be maxed out. Could running with a bad intake gasket for a while have toasted all four O2 sensors, and if so shouldn't at least one of their resepctive codes be set?
Thanks in advance as always,
-Keith
From reviewing other posts here, it seems that a P0420 is probably the post-cat O2 sensor on bank 1, but could also be the cat itself. It also seems that the rough idle could be caused by an O2 sensor (or sensors) that have failed or it could simply need a good fuel system cleaning, although I do run good fuel additives on a fairly regular basis. I replaced one of the pre-cat O2 sensors when the truck had about 60k, but the others I suspect are original.
I am wondering why none of the O2 sensors are reading a voltage, and why the fuel trims appear to be maxed out. Could running with a bad intake gasket for a while have toasted all four O2 sensors, and if so shouldn't at least one of their resepctive codes be set?
Thanks in advance as always,
-Keith