P20F2 SCR NOx Catalyst Efficiency Below Threshold (Bank 2)

P20F2 is the bank 2 twin of P20EE: the main SCR catalyst of the second exhaust line removes less NOx than required, judged by NOx sensors ahead of and behind it. CARB requires the NOx catalyst to be flagged once its conversion loss would push emissions past the regulatory multiple of the standard. No manufacturer documents P20F2 publicly; the widely used P20EE logic shows how such a monitor works. Ford's 2023 6.7 L diesel, for example, fails its catalyst below 55 % cumulative efficiency within a 200–320 °C inlet window, and GM compares measured with expected efficiency. A bank 2 code requires a dedicated SCR and sensor pair per bank. If both banks report low efficiency together, DEF quality or a shared supply fault is more likely than two worn catalysts. A speed limit may follow where the vehicle treats it as a DEF fault.

Likely causes

Symptoms

• Malfunction indicator lamp on
• DEF quality warning, possibly with a countdown to reduced speed

Repair estimate

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

Related codes

References: law.cornell.edu, fordservicecontent.com, gsi.ext.gm.com.