can a bad dpfe cause 172?

[stilov]

They happened at the same time...1st I will replace the dpfe and then change fuel filter, check fuel pressure, and check for vacuum leaks.

 

[rangerj]

Before you replace the DPFE make sure the EGR tube, the EGR exaust port, and EGR intake port, are clear. They become blocked with carbon deposits. Then check the vacuum hoses to the DPFE and FROM the DPFE to the EGR valve. Watch the EGR poppet valve stem move when you open and close the throttle.

If you do not have a vacuum leak then the O-2 sensor may be failing. The code 172 indicate that the O-2 sensor has stopped switching, or is switching slowly, and is spending more time in the lean mode than normally expected.

 

[projectSHO89]

can a bad dpfe cause 172?

No.

If you have multiple codes, always concentrate only on the first. Once it it resolved, reset the PCM and retest to see if any further codes are apparent.

Steve