Error codes P0420 P0123?

Tiny
SCHANT000
  • MEMBER
  • 1998 JEEP CHEROKEE
  • 2.1L
  • 5 CYL
  • 4WD
  • AUTOMATIC
  • 90,000 MILES
These error code were shown when tested by obd11 and I'm trying to fix the problem trying each suggestion but not sure if I'm even doing it right. Also note that while driving the cat converter fell completely off and still made it home afew blocks later. So the re is overheating that occurs every time it's driven, hesitant startup needing to pump gas to turn over and now most recent stalling out while driving usually when hot but Guage not working properly to inform me.
Monday, July 7th, 2025 AT 9:56 PM

1 Reply

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 52,235 POSTS
So the first code is because the catalytic converter is bad/fell off so you will need to repair that issue. The "pump the gas" and stalling issue can be the second code.

Code P0420 - Catalyst System Efficiency Below Threshold
Code P0123 - Throttle Position Sensor (TPS) Circuit High Input

I would check the wiring to the TPS and if okay replace the sensor, here is how in the images below. Also, please start a new thread for the overheating problem. Check out the images (below). Please upload pictures or videos in your response.
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Tuesday, July 8th, 2025 AT 8:27 AM

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