O2 Sensor Bank 2 Sensor 1 Circuit Wiring Diagram (2001-2004 3.0L V6 Ford Escape)

APPLIES TO: This H2OS 21 sensor circuit wiring diagram applies to the following vehicles:

This wiring diagram includes the following circuits:

Fuse 5: Located in the Battery Junction Box, front left corner of engine compartment.
Heated Oxygen Sensor Bank 2 Sensor 1 (HO2S 21): Located on the the exhaust manifold facing the radiator (front of vehicle).

Measures the O2 content of the exhaust gas of cylinders 4, 5, and 6 (Bank 2) before it enters the catalytic converter.

HO2S Bank 2 Sensor 1 Connector Pinout

Pin	Wire	Description
1	Light blue with orange stripe (LT BLU/ORG)	VPWR –Vehicle Power (12 Volts)
2	Yellow with light blue stripe (YEL/LT BLU)	HO2S 21 HEATER –PCM Supplied Ground (heater activation signal)
3	Orange (ORG)	SIG RTN –O2 Sensor Signal Ground
4	Gray with light blue stripe (GRY/LT BLU)	HO2S 21 SIG –O2 Sensor Signal

P0155 DIAGNOSTIC TESTS: The heater element of the H2OS 21 sensor can easily be tested with a multimeter. This tutorial will show you how:

You can find a complete list of wiring diagrams and diagnostic test tutorials here:

Here's a sample of the tutorials you'll find there:

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