Input/Output
The upstream and downstream HO2 S are colour coded to prevent incorrect fitting. The tips of the upstream sensors
are physically different to the tips of the downstream sensors.
The HO2 S are colour coded as follows:
l Upstream sensors (both banks) - orange.
l Downstream sensors (both banks) - grey.
The four HO2 S have a direct battery supply to the heater via fuse 2 located in the engine compartment fuse box.
The heater is driven by the ECM providing an earth path for the circuit as follows:
l Upstream LH bank via pin 19 of connector C0635 of the ECM.
l Upstream RH bank via pin 13 of connector C0635 of the ECM.
l Downstream LH bank via pin 7 of connector C0635 of the ECM.
l Downstream RH bank via pin 1 of connector C0635 of the ECM.
The HO2 S output signal is measured by the ECM as follows:
l Upstream LH bank via pin 15 of connector C0635 of the ECM.
l Upstream RH bank via pin 16 of connector C0635 of the ECM.
l Downstream LH bank via pin 17 of connector C0635 of the ECM.
l Downstream RH bank via pin 14 of connector C0635 of the ECM.
The HO2 S earth path for the signal is supplied by the ECM as follows:
l Upstream LH bank via pin 9 of connector C0635 of the ECM.
l Upstream RH bank via pin 10 of connector C0635 of the ECM.
l Downstream LH bank via pin 11 of connector C0635 of the ECM.
l Downstream RH bank via pin 8 of connector C0635 of the ECM.
The HO2 S voltage is difficult to measure using a multimeter, the output can be monitored using TestBook. A rich
mixture would read 500 to 1000 mV, a weak mixture would read 100 mV to 500 mV, the reading should switch from
rich to weak. The open loop default voltage is 450 mV, this is used by the ECM to set the air/ fuel ratio until the tip of
the HO2 S reaches operating temperature.
