LEMON Manuals: Even more car manuals for everyone
Home >> Jeep >> 1999 >> Grand Cherokee Laredo, 4.7 N >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Self-Diagnostic Tests >> DTC P0036: 1/2 O2 Sensor Heater Circuit Malfunction

DTC P0036: 1/2 O2 Sensor Heater Circuit Malfunction

NOTE: For connector terminal identification, see CONNECTOR IDENTIFICATION  . For circuit identification and wiring diagram, see GRAND CHEROKEE wiring diagram in WIRING DIAGRAMS article.
NOTE: DTC P0036: 1/2 O2 SENSOR HEATER CIRCUIT MALFUNCTION is monitored with ignition on and battery voltage more than 10.4 volts. DTC may be stored in Powertrain Control Module (PCM) when state of PCM relay control circuit between PCM and relay coil does not match desired state. Possible causes are: open fuse, open coil at Heated Oxygen Sensor (HO2S) heater relay, defective connectors or defective wiring.
NOTE: 1/2 HO2S is located in downstream position.
  1. Turn ignition on, with engine off. Using scan tool, read DTCs. If DTC SPECIFIC GOOD TRIP COUNTER is displayed and displayed count is "0", go to next step. If DTC SPECIFIC GOOD TRIP COUNTER is not displayed or displayed count is not "0", go to step 9).
  2. Turn ignition off. Check HO2S heater relay fuse. Fuse is located in Power Distribution Center (PDC). PDC is located next to battery. Refer to label under PDC cover for fuse location. If fuse is open, go to next step. If fuse is not open, go to step 4).
  3. Ensure ignition is off. Remove HO2S heater relay. Relay is located in Power Distribution Center (PDC). Refer to label under PDC cover for relay location. Remove HO2S heater relay fuse. Using an ohmmeter, check resistance between ground and HO2S heater relay connector, fused B+ circuit (Dark Green wire). If resistance is less than 5 ohms, repair fused B+ circuit for short to ground, then replace HO2S heater relay fuse. Perform TEST VER-5A. If resistance is 5 ohms or more, replace HO2S heater relay fuse. Perform TEST VER-5A.
  4. Ensure ignition is off. Ensure HO2S heater relay is still removed. Using an ohmmeter, check resistance between HO2S heater relay terminals No. 85 and 86. See Figure . If resistance is more than 100 ohms, replace HO2S heater relay. Perform TEST VER-5A. If resistance is 100 ohms or more, go to next step.
  5. Ensure ignition is off. Ensure HO2S heater relay is still removed. Remove HO2S heater relay fuse. Using ohmmeter, check resistance of HO2S heater relay fused B+ circuit (Dark Green wire) between HO2S heater relay fuse connector and PDC connector. If resistance is less than 5 ohms, repair open fused B+ circuit. Perform TEST VER-5A. If resistance is 5 ohms or more, go to next step.
  6. Ensure ignition is off. Ensure HO2S heater relay is still removed. Disconnect PCM connectors. PCM is located in engine compartment. See PCM LOCATION table under SYSTEM DIAGNOSTICS. Clean and/or repair connectors as necessary. Using ohmmeter, check resistance of HO2S heater relay control circuit (Light Blue wire) between HO2S heater relay connector and PCM connector. If resistance is less than 5 ohms, repair open control circuit. Perform TEST VER-5A. If resistance is 5 ohms or more, go to next step.
  7. Ensure ignition is off. Ensure HO2S heater relay is still removed. Ensure PCM connectors are still disconnected. Using ohmmeter, check resistance between ground and HO2S heater relay connector, control circuit (Light Blue wire). If resistance is less than 5 ohms, repair control circuit for short to ground. Perform TEST VER-5A. If resistance is 5 ohms or more, go to next step.
  8. At this time, PCM is assumed to be defective. Replace PCM. Perform TEST VER-5A.
  9. Turn ignition off. Visually inspect related connectors and wiring harness. Repair connectors and wiring harness as necessary. Perform TEST VER-5A. If connectors and wiring harness are okay, test is complete.
scientia non olet · About LEMON Manuals