Test TC-124A: 2/1 O2 Sensor Heater Failure
NOTE:
This test applies to AN body (2WD) equipped with 5.9L engine, and BE/BR bodies equipped with 5.9L heavy-duty engine or 8.0L engine only. For connector terminal identification, see CONNECTOR IDENTIFICATION . For component location and wiring diagram, see WIRING DIAGRAMS article.
NOTE:
Allow Heated Oxygen Sensor (HO2S) to cool to room temperature before checking resistance.
NOTE:
2/1 HO2S is located in right upstream position on models with 2 upstream HO2S.
- Turn ignition on, engine off. Wait 3 minutes. Using scan tool in SENSORS, monitor 2/1 HO2S voltage. Wait for voltage to stabilize at more than 4.5 volts. Go to next step.
- Using scan tool in ACTUATOR TESTS, perform HO2S heater test. Monitor 2/1 HO2S voltage for 2 minutes. If voltage is more than one volt, go to step 4) . If voltage is one volt or less, go to next step.
- Condition required to set DTC is not present at this time. O2 SENSOR HEATER FAILURE DTC sets if Powertrain Control Module (PCM) senses HO2S voltage at more than 3 volts for 30-90 seconds after a cold engine start. Possible causes are: open HO2S heater element circuit, HO2S failure, HO2S heater wiring failure, PCM failure, defective connections or wiring. Stop all actuator tests. Test is complete.
- Disconnect 2/1 HO2S connector. Inspect connector and terminals for damage. Repair connector and terminals as necessary and perform TEST VER-5A: ROAD TEST FOR OBD-II TROUBLE CODES . If connector and terminals are okay, go to next step.
- Ensure scan tool is actuating HO2S heater test. Using an external voltmeter, check voltage on HO2S ASD relay output circuit (Dark Green/Orange wire). If voltage is 10 volts or less, repair open ASD relay output circuit and perform TEST VER-5A: ROAD TEST FOR OBD-II TROUBLE CODES . If resistance is more than 10 volts, go to next step.
- Stop all actuator tests. Using an external ohmmeter, check resistance between HO2S (component side) terminal No. 1, ASD relay output circuit (White wire) and terminal No. 2, heater ground circuit (White wire). See Fig 1. If resistance is not 4-7 ohms, replace 2/1 HO2S and perform TEST VER-5A: ROAD TEST FOR OBD-II TROUBLE CODES . If resistance is 4-7 ohms, go to next step.
- Check resistance between ground and HO2S connector, heater ground circuit (Black/White wire). If resistance is 5 ohms or more, repair open heater ground circuit and perform TEST VER-5A: ROAD TEST FOR OBD-II TROUBLE CODES . If resistance is less than 5 ohms, replace 2/1 HO2S and perform TEST VER-5A: ROAD TEST FOR OBD-II TROUBLE CODES .
NOTE:
A break in test sequence occurs at this point. Sequence skips from TEST TC124A to TEST TC126A. No tests have been omitted.