LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Chrysler >> 2001 >> PT Cruiser Base, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0139: 1/2 O2 Sensor Slow Response >> Testing
April 5, 2026: LEMON Manuals is launched! Read the announcement.

DTC P0139: 1/2 O2 Sensor Slow Response: Testing

NOTE: Before proceeding, check for contaminates that may have damaged HO2S such as contaminated fuel, unapproved silicone, oil and coolant. Record freeze frame data that was set with DTC.
  1. Turn ignition on. Using scan tool, read DTCs. If GOOD TRIP is displayed and equal to zero, go to next step. If GOOD TRIP is not displayed and equal to zero, go to step  9 .
  2. Start engine. Check for exhaust leaks between engine and HO2S. If no leaks are present, go to next step. If any leaks are found, repair as necessary.
  3. With engine idling, measure voltage drop (backprobe connectors with voltmeter) of signal circuit (Tan/White wire) between 1/2 HO2S harness connector and terminal No. 51 at PCM C2 harness connector. See Figure and Figure . If voltage drop is less than .1 volt, go to next step. If voltage drop is .1 volt or more, repair high resistance in signal circuit.
  4. With engine idling, measure voltage drop (backprobe connectors with voltmeter) of sensor ground circuit (Black/Orange wire) between 1/2 HO2S harness connector and terminal No. 27 at PCM C1 harness connector. If voltage drop is less than .1 volt, go to next step. If voltage drop is .1 volt or more, repair high resistance in sensor ground circuit.
  5. Turn ignition off. Allow HO2S to cool to room temperature. Disconnect 1/2 HO2S harness connector. Measure resistance of HO2S heater element between HO2S terminals No. 1 and 2 (component side). See Figure . If resistance is 4-7 ohms, go to next step. If resistance is not 4-7 ohms, replace 1/2 HO2S.
  6. Measure resistance between ground and heater ground circuit (Black wire) at 1/2 HO2S harness connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open between 1/2 HO2S harness connector and ground point located on left front strut tower.
  7. Reconnect PCM harness connectors. Turn ignition on. Using scan tool, actuate O2 HEATER TEST. Measure voltage between ground and ASD relay output circuit (Dark Green/Orange wire) at 1/2 HO2S harness connector. If voltage is more than 11 volts, go to next step. If voltage is 11 volts or less, repair open in ASD relay output circuit.
  8. Replace 1/2 HO2S. Operate vehicle under conditions noted in freeze frame. It may be necessary to operate vehicle for more than 2 drive cycles. Using scan tool, monitor 1/2 HO2S voltage and ensure good voltage activity. If DTC does not reset, test is complete. If DTC resets, replace PCM.
  9. Conditions that set DTC are not present at this time. Perform the following to help identify intermittent condition:
    • With engine running at normal operating temperature, wiggle related wiring harness while monitoring related parameters on scan tool. If voltage changes or DTC sets while wiggling wiring harness, repair connectors or wiring harness where wiggling caused voltage to change or DTC to set.
    • Review freeze frame information on scan tool. Duplicate conditions present when DTC was set.
    • Refer to any Technical Service Bulletins (TSBs) that may apply.
    • Visually inspect related wiring harness. Check for chafed, pierced, pinched or partially broken wires.
    • Visually inspect related wiring harness connectors. Check for broken, bent, pushed out or corroded terminals.

    If a problem is found, repair as necessary. If no problems are found, test is complete.

scientia non olet · About LEMON Manuals