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Home › Jeep › 2003 › Grand Cherokee Overland › Repair and Diagnosis › External Pages › Different car › Section 30 (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 2003 Jeep Wrangler. However, it is still accessible from the selected car via links, so may be relevant.
    NOTE: Check for contaminants that may have damaged the O2 Sensor: contaminated fuel, unapproved silicone, oil and coolant.
  1. With the ignition on and the engine not running, read the DTCs and record the related Freeze Frame data. Is the Good Trip Counter displayed and equal to zero? If yes, go to the next step. If no, refer to the INTERMITTENT CONDITION  under SELF-DIAGNOSTIC SYSTEM.
    2. NOTE: Wait a minimum of 8 minutes to allow the O2 Sensor to cool down before continuing the test.
  2. 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 0.1 and 0.3 volt during the Heater test? If yes, refer to the INTERMITTENT CONDITION  under SELF-DIAGNOSTIC SYSTEM. If no, go to next step.
  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 at 70°F (21.1°C)? 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 Modulated (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 10.0 volts? If yes, go to next step. If no, repair the open in the O2 Sensor Heater Supply circuit.
  5. Turn the ignition off. Disconnect the PCM harness connectors. Remove the O2 Heater Relay, if it applies to the O2 Sensor being tested. Measure the resistance of the O2 Heater Control circuit (PWM) from the O2 Sensor to the PCM harness connector if it applies to the O2 Sensor being tested. Otherwise, measure the resistance of the (K512) O2 Heater Relay Control circuit from the O2 Heater Relay to the PCM harness connector, if it applies to the O2 Sensor being tested. Is the resistance below 5.0 ohms? If yes, go to next step. If no, repair open/high resistance in the O2 Heater Control circuit.
    6. NOTE: Before beginning this test, verify what type of Heated O2 Sensor is being tested, either the PWM Heated O2 Sensor or the Heater Relay controlled Heated O2 Sensor.
  6. Remove the O2 Heater 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. NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.
  7. Using the wiring diagram as a guide, inspect the wire harness and connectors. Pay particular attention to all power and ground circuits. If there are no possible causes remaining, replace PCM. Program the new PCM. See PROGRAMMING .
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