2001 Plymouth Neon Base, AutomaticFACTORY OEM SERVICE PROCEDURE

DTC P0135: 1/1 O2 Sensor Heater Failure: Testing

  1. Turn ignition on. Using scan tool, read DTCs. If GOOD TRIP is displayed and equal to zero, go to step  3 . If GOOD TRIP is not displayed and equal to zero, go to next step.
  2. Turn ignition off. Wait at least 8 minutes to allow HO2S to cool until HO2S voltage has stabilized to between .4 and .6 volt. Turn ignition on. Using scan tool, actuate O2 HEATER TEST and monitor 1/1 HO2S voltage for at least 2 minutes. If voltage stays between .4 and .6 volt, go to next step. If voltage does not stay between .4 and .6 volt, go to step  8 .
  3. Turn ignition off. Disconnect 1/1 HO2S harness connector. Measure resistance of HO2S heater element between HO2S terminals No. 1 and 2. See Fig 1 . If resistance is 4-7 ohms, go to next step. If resistance is not 4-7 ohms, replace HO2S.
  4. Turn ignition off. Disconnect PCM harness connectors. PCM is located in engine compartment, between air cleaner and radiator. Measure resistance of heater control circuit (Orange/Red wire) between 1/1 HO2S harness connector and terminal No. 18 at PCM C1 harness connector. See Figure . If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in heater control circuit.
  5. Measure resistance between ground and heater control circuit (Orange/Red wire) at 1/1 HO2S harness connector. If resistance is 5 ohms or more, go to next step. If resistance is less than 5 ohms, repair short to ground in heater control circuit.
  6. Turn ignition off. Reconnect PCM harness connectors. Ensure 1/1 HO2S is still disconnected. Using scan tool, actuate O2 HEATER TEST. Measure voltage between ground and ASD relay output circuit (Dark Green/Orange wire) at 1/1 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.
  7. If no other possible causes are remaining, replace PCM.
  8. 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.

Fig 1: Identifying Upstream (1/1) Oxygen Sensor Connector Terminals
G00014436Courtesy of DAIMLERCHRYSLER CORPORATION
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

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