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Test TC-124A - O2 Sensor 2/1 Heater Failure

NOTE: For connector terminal identification, see CONNECTOR IDENTIFICATION in SELF-DIAGNOSTICS section in this article. For wiring diagram, see WIRING DIAGRAMS - 2.7L article.
  1. For O2 sensor/model identification see O2 SENSOR 2/1 IDENTIFICATION table. Using scan tool, read trouble codes. If any other O2 SENSOR 2/1 DTCs are set, perform other tests first. See DTC TEST. If no other O2 SENSOR 2/1 DTCs are set, go to next step.
  2. Turn ignition off. Wait 8 minutes. Turn ignition on. Using scan tool, monitor O2S 2/1 voltage. Wait for voltage reading to stabilize between .4-.6 volt. Using scan tool, actuate O2S 2/1 heater test. Monitor O2S2/1 voltage for 2 minutes. If O2S 2/1 voltage is still .4-.6 volt, go to step 5). If O2S 1/2 voltage is not .4-.6 volt, go to next step.
  3. If referenced to this test from TEST TC-120A, return to TEST TC-120A and continue with diagnostic procedure. If not referenced to this test from TEST TC-120A, go to next step.
  4. Condition to set trouble code is not present at this time. O2S 2/1 HEATER FAILURE DTC sets using O2S signal voltage readings during O2S cool-down period, with heater off compared to O2S signal voltage readings with heater on. Possible causes are: open heater element circuit, O2S 2/1 failure, O2 heater failure, PCM failure, faulty connectors or wiring, ASD relay fuses or open ASD relay circuit. Stop all actuator tests. Test is complete. Perform TEST VER-5A.
  5. Disconnect O2S 2/1 connector. Inspect O2S 2/1 connector for damaged, pushed out or miswired terminals. Repair connector as necessary. Perform TEST VER-5A. If connector is okay, go to next step.
  6. With scan tool still actuating O2S 2/1 heater test, using a voltmeter, check voltage of ASD relay output circuit on O2S 2/1 connector (harness side). See O2S 2/1 CONNECTOR WIRE IDENTIFICATION (HARNESS SIDE) table. If voltage is more than 10.5 volts, go to next step. If voltage is 10.5 volts or less, repair open ASD relay output circuit. Perform TEST VER-5A.
  7. Using scan tool, stop actuator test. Allow vehicle to cool to room temperature. Using an ohmmeter, check resistance of O2S 2/1 heater element. Measure resistance between 2 White wires on O2S 2/1 connector (component side). See O2S 2/1 CONNECTOR WIRE IDENTIFICATION (COMPONENT SIDE) table. If resistance is 4-7 ohms, go to next step. If resistance is not 4-7 ohms, replace O2S 2/1. Perform TEST VER-5A.
  8. Using an ohmmeter, measure resistance of O2S 2/1 heater ground circuit between O2S 2/1 connector (harness side) and ground. See O2S 2/1 CONNECTOR WIRE IDENTIFICATION (HARNESS SIDE) table. If resistance is less than 5 ohms, replace O2S 2/1. Perform TEST VER-5A. If resistance is 5 ohms or more, repair open O2S 2/1 heater ground circuit. Perform TEST VER-5A.
O2S 2/1 CONNECTOR WIRE IDENTIFICATION (COMPONENT SIDE)

Application Wire Color
O2S 2/1 Signal Circuit Black
O2S 2/1 ASD Relay Output Circuit White
O2S 2/1 Heater Ground Circuit White
O2S 2/1 Ground Circuit Gray
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