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Home › Jeep › 2003 › Grand Cherokee Overland › Repair and Diagnosis › External Pages › Different car › Section 5 (Engine Controls - Self-Diagnostics) › Diagnostic Tests › DTC P0135: 1/1 O2 Sensor Heater Failure, DTC P0141: 1/2 O2 Sensor Heater Failure, DTC P0155: 2/1 O2 Sensor Heater Failure Or DTC P0161: 2/2 O2 Sensor Heater Failure › Testing

DTC P0135: 1/1 O2 Sensor Heater Failure, DTC P0141: 1/2 O2 Sensor Heater Failure, DTC P0155: 2/1 O2 Sensor Heater Failure Or DTC P0161: 2/2 O2 Sensor Heater Failure: Testing

WARNING: This page is about a different car, the 2002 Jeep Grand Cherokee. However, it is still accessible from the selected car via links, so may be relevant.
    NOTE: Wait a minimum of 8 minutes to allow the O2 Sensor to cool down before continuing the test.
  1. Turn ignition on, engine not running. With the DRBIII®, actuate the O2 Heater Test. With the DRBIII®, monitor O2 Sensor voltage for at least 2 minutes. Does the voltage stabilize between 0.4 and 0.6 volt during the Heater test? If yes, go to next step. If no, go to step  3.
    2. WARNING: When the engine is operating, do not stand in a direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing.
  2. The conditions that set the DTC are not present at this time. The following may help in identifying the intermittent condition. With the engine running at normal operating temperature, monitor the DRBIII® parameters related to the DTC while wiggling the wiring harness. Look for parameter values to change and/or a DTC to set. Review the DRBIII® Freeze Frame information. If possible, try to duplicate the conditions under which the DTC was set. Refer to any Technical Service Bulletins (TSB) that may apply. Visually inspect the related wiring harness. Look for any chafed, pierced, pinched, or partially broken wires. Visually inspect the related wiring harness connectors. Look for broken, bent, pushed out, or corroded terminals. Were any of the above conditions present? If yes, repair as necessary. If no, test is complete.
  3. Turn ignition off. Allow HO2S to cool down to room temperature. Disconnect the O2 Sensor harness connector related to DTC. Measure the resistance across the O2 Sensor Heater element component side. The resistance value increases with temperature. Is the resistance between 4.0 and 5.0 ohms? If yes, go to next step. If no, replace the O2 Sensor.
    4. NOTE: This test depends on the type of Heated O2 Sensor being tested. The Pulse Width Modulate (PWM) Heated O2 Sensor uses the ASD Relay to supply voltage to the heater element and the other type of Heated O2 Sensor uses an O2 Sensor Downstream Relay.
  4. Turn ignition on, engine not running. With the DRBIII®, actuate the O2 Heater Test. Measure the voltage on the O2 Heater supply circuit at the O2 Sensor harness connector. Is the voltage above 11.0 volts? If yes, go to next step. If no, repair the open in the O2 Sensor Heater Supply circuit.
    5. NOTE: On the 1/1 and 2/1 O2 Sensors, the heater control circuit is controlled by the PCM. On the 1/2 O2 Sensor, the heater ground circuit goes to chassis ground.
  5. Turn the ignition off. On 1/1 and 2/1 O2 Sensors, disconnect the PCM harness connectors. Measure the resistance of the Heater Control circuit from the PCM connector to the O2 Sensor harness connector. Is the resistance below 5.0 ohms? If yes, reconnect PCM harness connectors and go to next step. If no, repair open in Heater Control circuit. On 1/2 O2 Sensor, measure the resistance between ground and the O2 Sensor Ground circuit at the O2 Sensor harness connector. Is the resistance below 5.0 ohms? If yes, go to next step. If no, repair open in the O2 Sensor Ground circuit.
  6. Remove the O2 Downstream Relay from power distribution center if it applies to the type of Heated O2 Sensor being tested. If you are testing a Pulse Width Modulated Heated O2 Sensor, measure the resistance between ground and the heater control circuit at the disconnected O2 Sensor harness connector. If you are testing a Heated O2 Sensor that uses an O2 Sensor Downstream Relay to supply power to the O2 Sensor Heater, measure the resistance between ground and O2 Sensor downstream heater relay control circuit at O2 Downstream Relay connector in PDC. On all applications, is the resistance below 100 ohms? If yes, repair the short to ground in the Heater Control circuit or O2 Sensor Downstream Heater Relay Control circuit. If no, go to next step.
  7. There are no possible causes remaining, replace PCM. Program the new PCM. See PROGRAMMING .
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