Code P0240

Tiny
DIGGOD1
  • MEMBER
  • 2003 GMC ENVOY
  • 4.2L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 160,000 MILES
Replaced catalytic converter and both o2 sensor still have p0420.
Thursday, November 4th, 2021 AT 9:37 AM

1 Reply

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
Hi,

The code simply indicates the converter is no longer doing its job. Did you reset or clear the code? It should reset itself after three consecutive ignition cycles without a problem. Are there any other codes stored?

Since everything is new, we may need to confirm the sensors are working properly. There could be a wiring issue.

Take a look through this link. It explains what to test.

https://www.2carpros.com/articles/how-to-test-an-oxygen-sensor-02-sensor

Let me know if you have a live data scanner and if there are any other codes stored.

Take care,

Joe
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Thursday, November 4th, 2021 AT 7:45 PM

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