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DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.

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HOMESERVICE MANUALSJEEP2009GRAND CHEROKEE LAREDO, 3.0 M, AWDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT VARIANT/TRIMSECTION 9 (DTCS P0125 TO P0196 - GAS)P0135-O2 SENSOR 1/1 HEATER PERFORMANCEDIAGNOSTIC TEST

2009 Jeep Grand Cherokee Laredo, 3.0 M, AWD

Diagnostic Test

2009 Jeep Grand Cherokee Laredo, 3.0 M, AWDSECTION Diagnostic Test

WARNING: This page is about a different variant/trim than selected.

O2 SENSOR HEATER OPERATION
1. Turn the ignition off.
  NOTE: Wait a minimum of 8 minutes to allow the O2 Sensor to cool down before continuing the test. Allow the O2 Sensor voltage to stabilize between 4.6 and 5.0 volts.
2. Ignition on, engine not running.
3. With a scan tool, actuate the 1/1 O2 Heater Test.
4. With the scan tool, monitor 1/1 O2 Sensor voltage for at least 2 minutes.
  Does the voltage stay above 4.5 volts?
  
  Yes
  - Go to step 2
  No
  - Refer to the INTERMITTENT CONDITION Diagnostic Procedure. See DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure .
O2 SENSOR HEATER ELEMENT
1. Turn the ignition off.
  NOTE: Allow the O2 sensor to cool down to room temperature.
2. Disconnect the O2 Sensor harness connector.
3. Measure the resistance of the O2 Heater Element across the 1/1 O2 Sensor connector between the O2 Heater Control terminal and the Heater ground terminal.
  NOTE: O2 Heater Element resistance values should be measured at 21.1°C (70°F). The resistance value will vary with different temperature values.
  
  Is the resistance of the O2 Sensor Heater Element between 2.0 and 30.0 ohms?
  
  Yes
  - Go to step 3
  No
  - Verify that there is good pin to terminal contact in the Sensor and Control Module connectors. If OK, replace the O2 Sensor.
  - Perform the POWERTRAIN VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure .
(K99) O2 1/1 HEATER CONTROL CIRCUIT OPEN

Fig 1: Measuring Resistance Of O2 Sensor Heater Control Circuit From O2 Sensor Harness Connector To Appropriate Terminal Of Special Tool #8815
Courtesy of CHRYSLER LLC
1. Disconnect the C2 PCM harness connector.
  CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install PCM Pinout Box 8815 to perform diagnosis.
2. Measure the resistance of the (K99) O2 1/1 Heater Control circuit from the O2 harness connector to the appropriate terminal of special tool #8815.
  Is the resistance below 0.5 of an ohm?
  
  Yes
  - Go to step 4
  No
  - Repair the excessive resistance in the (K99) O2 1/1 Heater Control circuit.
  - Perform the POWERTRAIN VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure .
(Z42) O2 1/1 HEATER GROUND CIRCUIT OPEN

Fig 2: Measuring Resistance Between Ground And O2 Sensor Heater Ground Circuit In O2 Sensor Harness Connector
Courtesy of CHRYSLER LLC
1. Measure the resistance between ground and the (Z42) O2 1/1 Heater ground circuit in the O2 Sensor harness connector.
  Is the resistance below 0.5 of an ohm?
  
  Yes
  - Go to step 5
  No
  - Repair the excessive resistance in the (Z42) O2 1/1 Heater ground circuit.
  - Perform the POWERTRAIN VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure .
POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Oxygen Sensor 1/1 and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched, or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the Sensor and Control Module connectors.
4. Refer to any Technical Service Bulletins that may apply.
  Were there any problems found?
  
  Yes
  - Repair as necessary.
  - Perform the POWERTRAIN VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure .
  No
  - Replace and program the Powertrain Control Module per Service Information.
  - Perform the POWERTRAIN VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure .

RENDER: 1.0x

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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.