P220B: NOx Sensor Supply Voltage Circuit (Bank 1 Sensor 2)

What does P220B mean?

P220B concerns the second NOx sensor on bank 1, the one behind the SCR catalyst whose reading proves how well NOx is being converted. Its operating voltage is outside the allowed band. Ford applies the same 8.5 to 16.5 V window as for the front sensor; GM's 3.0L LZ0 flags under 9.9 V (Type B), and VW's 2014 Touareg TDI compares battery and sensor supply, faulting a gap above 1.5 V. GM's 2018 Equinox and Terrain with the 1.6L diesel (LH7) could log P220B through a software issue; PIP5615A points to bulletin 19-NA-009 and an ECM calibration. Volvo and Mack class it as a supply problem, not a sensor failure. Without this sensor the catalyst efficiency check cannot run. P220A is the front sensor.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• Malfunction indicator lamp on
• Downstream NOx sensor shows no value
• SCR efficiency monitor stays incomplete

Common causes

• High Fuse, relay or ground fault in the downstream sensor supply
• Medium Supply wire to the rear sensor damaged under the vehicle
• Low ECM calibration (GM 1.6L LH7 2018, PIP5615A / 19-NA-009)

Likelihood is a general estimate across vehicles; your make and model may differ.