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Home >> Dodge and Ram >> 1999 >> Durango 5.9 Z, 4WD, Part Time >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Self-Diagnostic Tests >> DTC P0139: 1/2 O2 Sensor Slow Response
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DTC P0139: 1/2 O2 Sensor Slow Response

NOTE: For connector terminal identification, see CONNECTOR IDENTIFICATION  . For circuit identification and wiring diagram, see DURANGO wiring diagram in WIRING DIAGRAMS article.
NOTE: DTC P0139: 1/2 O2 SENSOR SLOW RESPONSE is monitored with engine coolant temperature more than 147°F (63.9°C), after reaching a vehicle speed of 10 MPH, and throttle remains open (off idle) for 2 minutes and subsequently bringing vehicle to a stop and allowing engine to idle in Drive (A/T) or Neutral (M/T). DTC may be stored in Powertrain Control Module (PCM) when PCM senses that 1/2 Heated Oxygen Sensor (HO2S) voltage is switching from less than .27 volt to more than .62 volt and back less times than required. Possible causes are: engine mechanical problem, exhaust leak, defective 1/2 HO2S, defective PCM, defective connectors or defective wiring.
NOTE: 1/2 HO2S is located in downstream position.
  1. Start engine and allow it to idle. Check exhaust system for leaks between engine and catalytic converter. Repair exhaust system as necessary. Perform TEST VER-5A. If exhaust system is okay, go to next step.
  2. With engine still running, check exhaust system for excessive smoke caused by coolant or oil consumption. Repair engine mechanical problem as necessary and replace 1/2 HO2S. Perform TEST VER-5A. If engine mechanical condition is okay, go to next step.
  3. Turn engine off. Disconnect 1/2 HO2S connector. Clean and/or repair connector as necessary. Using an ohmmeter, check resistance between ground and 1/2 HO2S connector, sensor ground circuit (Black/Light Blue wire). If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open sensor ground circuit. Perform TEST VER-5A.
  4. Ensure 1/2 HO2S connector is still disconnected. Visually inspect related connectors and wiring harness for damage. Repair connectors and wiring harness as necessary. Perform TEST VER-5A. If connectors and wiring harness are okay, go to next step.
  5. Ensure ignition is off. Ensure 1/2 HO2S connector is still disconnected. Disconnect PCM connectors. PCM is located in engine compartment. See PCM LOCATION table under SYSTEM DIAGNOSTICS. Visually inspect related connectors and wiring harness for damage. Repair connectors and wiring harness as necessary. Perform TEST VER-5A. If connectors and wiring harness are okay, go to next step.
  6. At this time, 1/2 HO2S is assumed to be defective. Replace 1/2 HO2S. Perform TEST VER-5A.
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