It indicates the circuit is open. Check the wiring to the ECU from the O2 sensor.
1. Ensure truck power is OFF.
2. Change DMM to ohms scale. Verify DMM zero reading.
3. Disconnect the oxygen (O2) sensor connector, the indicated PDM connector, and the indicated ECU
connector.
4. At the sensor harness connector, measure the resistance on the sensor supply wire between the sensor
connector and the PDM connector.
Is resistance less than 0.5 ohms?
YES: Go to Step 5.
NO: The supply wire has an open circuit. Locate and repair/replace open wire/connection. Refer to
appropriate Wire Harness Repair manual, depending on lift truck model.
5. Measure the resistance of the sensor drive wire between the sensor connector and the ECU connector.
Is resistance less than 0.5 ohms?
YES: Go to CAUSE B.
NO: The supply wire has an open circuit. Locate and repair/replace open wire/connection. Check that
counterweight has not crushed wire harness, if counterweight was removed. Refer to appropriate Wire
Harness Repair manual, depending on lift truck model.
Diagnostic Trouble Codes Electrical System
Check

Yes sir. Thanks I know what the codes means just trying to figure out any other diagnostics to perform as we have already replaced the O2 sensors.

522740-5 Pre-Cat Bank 2 Heater is Open Circuit..