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DTC P0139: 1/2 O2 Sensor Slow Response

NOTE: For connector terminal ID, see CONNECTOR IDENTIFICATION  . For wiring diagram, see WIRING DIAGRAMS article.
NOTE: The 1/2 oxygen sensor may also be referred to as downstream oxygen sensor. 1/2 oxygen sensor slow response is monitored when the engine is idling. For the first part of the test, if limits are exceeded, the test passes. If limits are not exceeded, the second part of test is performed when ambient/battery temperature sensor reading is more than 44°F (6.7°C), baro is more than 22.13" H2 O of vacuum, battery voltage is more than 10.5 volts, MAP sensor is more than 11.79" H2 O of vacuum but less than 18.15" H2 O of vacuum, engine speed is more than 1350 RPM but less than 2200 RPM and vehicle speed is more than 50 MPH but less than 65 MPH. DTC may be stored in Powertrain Control Module (PCM) if 1/2 oxygen sensor signal voltage is switching from less than .39 volt to more than .58 volt and back fewer times than required. Possible causes are: exhaust leak, defective 1/2 oxygen sensor, or defective connectors or wiring.
  1. Turn ignition on with engine off. Using scan tool, check for DTCs. If DTC SPECIFIC GOOD TRIP counter is displayed and equal to zero, go to next step. If DTC SPECIFIC GOOD TRIP counter is not displayed and equal to zero, go to step  9 .
  2. Ensure ignition is on with engine off. Using scan tool, actuate oxygen sensor heater test and then use scan tool to monitor 1/2 oxygen sensor voltage for 2-3 minutes. Oxygen sensor heater test may also be referred to as O2 heater test. If 1/2 oxygen sensor voltage becomes less than 1.5 volts within 2-3 minutes, stop oxygen sensor heater test. Go to next step. If 1/2 oxygen sensor voltage does not become less than 1.5 volts within 2-3 minutes, go to step  6 .
  3. Start engine and allow engine to idle. Check for exhaust leaks between engine and 1/2 oxygen sensor. On 4.7L Calif. emission vehicles, 1/2 oxygen sensor is located on driver's side exhaust pipe, just below small catalytic converter. On 4.7L except Calif. emission vehicles, 5.2L and 5.9L, 1/2 oxygen sensor is located on exhaust pipe behind catalytic converter. On all models, if no exhaust leaks exist, go to next step. If exhaust leaks exist, repair exhaust system as necessary. Perform TEST VER-5  .
  4. Shut engine off. Using voltmeter, backprobe terminal No. 3 (Black/Light Blue wire) on 1/2 oxygen sensor connector and terminal No. 4 (Black/Light Blue wire) on PCM connector C1. This is the ground circuit for 1/2 oxygen sensor. PCM is located at passenger's side front corner of engine compartment on inner fender panel. Start engine and allow engine to idle. Warm engine to normal operating temperature and note voltage reading with engine idling. If voltage is less than .1 volt, go to next step. If voltage is .1 volt or more, repair high resistance on Black/Light Blue wire between 1/2 oxygen sensor and PCM. Perform TEST VER-5  .
  5. Shut engine off. Using voltmeter, backprobe terminal No. 4 (Tan/White wire on 4.7L or Orange/Black wire on 5.2L and 5.9L) on 1/2 oxygen sensor connector and terminal No. 25 (Tan/White wire on 4.7L or Orange/Black wire on 5.2L and 5.9L) on PCM connector C1. This is the signal circuit for 1/2 oxygen sensor. Start engine and allow engine to idle. Warm engine to normal operating temperature and note voltage reading with engine idling. If voltage is less than .1 volt, shut engine off. Replace 1/2 oxygen sensor. Perform TEST VER-5  . If voltage is .1 volt or more, repair high resistance on Tan/White wire (4.7L) or Orange/Black wire (5.2L and 5.9L) between 1/2 oxygen sensor and PCM. Perform TEST VER-5  .
  6. Stop actuation of oxygen sensor heater test. Turn ignition off. Disconnect 1/2 oxygen sensor connector. On 4.7L Calif. emission vehicles, 1/2 oxygen sensor is located on driver's side exhaust pipe, just below small catalytic converter. On 4.7L except Calif. emission vehicles, 5.2L and 5.9L, 1/2 oxygen sensor is located on exhaust pipe behind catalytic converter. On all models, turn ignition on with engine off. Using scan tool, actuate oxygen sensor heater test. Using voltmeter, check voltage at terminal No. 1 (Dark Green/Pink wire on 4.7L Calif. emission vehicles or Orange/Dark Green on 4.7L except Calif. emission vehicles, 5.2L and 5.9L) on 1/2 oxygen sensor connector. If voltage is 11 volts or less, stop oxygen sensor heater test. Go to next step. If voltage is more than 11 volts, go to step  8 .
  7. On 4.7L Calif. emission vehicles if voltage is 11 volts or less, repair open on Dark Green/Pink wire between oxygen sensor downstream heater relay and 1/2 oxygen sensor. It may be necessary to check operation of oxygen sensor downstream heater relay and check for open Orange/Dark Green wire between oxygen sensor downstream heater relay, joint connector No. 2 and fuse "A" (15-amp). It may be necessary to check fuse No. 3 (30-amp) as it supplies battery voltage on Gray wire to fuse "A". Fuse "A" which may also be referred to as O2 SSR fuse, fuse No. 3, joint connector No. 2 and oxygen sensor downstream heater relay are located in power distribution center. See Fig 1 . Oxygen sensor downstream heater relay may be referred to as oxygen downstream relay. On 4.7L except Calif. emission vehicles, 5.2L and 5.9L if voltage is 11 volts or less, repair open on Orange/Dark Green wire between fuse "A" (15-amp) and 1/2 oxygen sensor. It may be necessary to check for open on Dark Green/Orange wire between Auto Shutdown (ASD) relay, joint connector No. 2 and fuse "A". Fuse "A" which may also be referred to as O2 SSR fuse, ASD relay and joint connector No. 2 are located in power distribution center. See Fig 1 . On all models, power distribution center is located at driver's side front corner of engine compartment, near battery. Perform TEST VER-5  .
  8. Stop actuation of oxygen sensor heater test. Turn ignition off. Ensure 1/2 oxygen sensor connector is still disconnected. Using ohmmeter, check resistance between ground and terminal No. 2 (Black wire) on 1/2 oxygen sensor connector. If resistance is less than 5 ohms, replace 1/2 oxygen sensor. Perform TEST VER-5  . If resistance is 5 ohms or more, repair open on Black wire between 1/2 oxygen sensor and ground connection. Ground connection is located near front of passenger's side of engine, below A/C compressor. Perform TEST VER-5  .
  9. Start engine and allow engine to idle. Check for exhaust leaks between engine and 1/2 oxygen sensor. On 4.7L Calif. emission vehicles, 1/2 oxygen sensor is located on driver's side exhaust pipe, just below small catalytic converter. On 4.7L except Calif. emission vehicles, 5.2L and 5.9L, 1/2 oxygen sensor is located on exhaust pipe behind catalytic converter. On all models, if no exhaust leaks exist, go to next step. If exhaust leaks exist, repair exhaust system as necessary. Perform TEST VER-5  .
  10. With engine idling, wiggle wiring harness and connectors between PCM and 1/2 oxygen sensor while noting DTC SPECIFIC GOOD TRIP counter. PCM is located at passenger's side front corner of engine compartment on inner fender panel. If DTC SPECIFIC GOOD TRIP counter does not change to zero while wiggling wiring harness and connectors, go to next step. If DTC SPECIFIC GOOD TRIP counter changes to zero while wiggling wiring harness and connectors, repair wiring or connectors between PCM and 1/2 oxygen sensor as necessary. Perform TEST VER-5  .
  11. Shut engine off. Ensure ignition is off. Disconnect 1/2 oxygen sensor connector and PCM connectors. Inspect 1/2 oxygen sensor connector and PCM connectors for corroded, pushed out, miswired or damaged terminals. Inspect wiring harness between PCM and 1/2 oxygen sensor for any possible intermittent problems. Also, check for related Technical Service Bulletins (TSBs). If terminals are not corroded, pushed out or damaged and wiring harness is okay, test is complete. If terminals are corroded, pushed out or damaged or wiring harness is damaged, repair as necessary. Perform TEST VER-5  .
    Fig 1: Locating Fuses, Relays, Joint Connectors & Identifying Cavities In Power Distribution Center
    G00016661Courtesy of DAIMLERCHRYSLER CORPORATION
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