LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Jeep >> 1999 >> Grand Cherokee Laredo, 4.7 N >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Self-Diagnostic Tests >> DTC P0157: 2/2 O2S Volts Shorted To Ground
April 5, 2026: LEMON Manuals is launched! Read the announcement.

DTC P0157: 2/2 O2S Volts Shorted To Ground

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 P0157: 2/2 O2S VOLTS SHORTED TO GROUND is monitored with engine coolant temperature at more than 170°F (76.7°C) on previous ignition on, after a cold start, engine coolant temperature less than 98°F (36.7°C) and ambient/battery temperature is within 27°F (2.8°C), plus or minus, of engine coolant temperature. DTC may be stored in Powertrain Control Module (PCM) when PCM senses that 2/2 Heated Oxygen Sensor (HO2S) voltage is less than .156 volt for 28 seconds after engine is subsequently started. Possible causes are: defective 2/2 HO2S, defective PCM, defective connectors or defective wiring.
NOTE: 2/2 HO2S is located in downstream position.
  1. 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 8).
  2. If engine is warm, turn engine off for 15 minutes to allow 2/2 HO2S to cool down. Turn ignition on, with engine off. Using scan tool, read 2/2 HO2S voltage. If voltage is less than .16 volt, go to next step. If voltage is .16 volt or more, go to step 8).
  3. Turn ignition off. Disconnect 2/2 HO2S connector. Visually inspect connector for corroded, damaged, pushed-out or miswired terminals. Repair connector as necessary. Perform TEST VER-5A. If connector is okay, go to next step.
  4. Ensure ignition is off. If engine is warm, wait 15 minutes to allow 2/2 HO2S to cool down. Ensure 2/2 HO2S connector is still disconnected. Turn ignition on, with engine off. Using scan tool, read 2/2 HO2S voltage. If voltage is less than .16 volt, go to next step. If voltage is .16 volt or more, replace 2/2 HO2S. Perform TEST VER-5A.
  5. Ensure ignition is off. Ensure 2/2 HO2S connector is still disconnected. Disconnect PCM connectors. PCM is located in engine compartment. See PCM LOCATION table under SYSTEM DIAGNOSTICS. Clean and/or repair connectors as necessary. Using an ohmmeter, check resistance between 2/2 HO2S connector, signal circuit (Pink/White wire) and sensor ground circuit (Black/Light Blue wire). If resistance is 5 ohms or more, go to next step. If resistance is less than 5 ohms, repair signal circuit for short to sensor ground circuit. Perform TEST VER-5A.
  6. Ensure ignition is off. Ensure 2/2 HO2S and PCM connectors are still disconnected. Using ohmmeter, check resistance between ground and 2/2 HO2S signal circuit (Pink/White wire). If resistance is 5 ohms or more, go to next step. If resistance is less than 5 ohms, repair 2/2 HO2S signal circuit for short to ground. Perform TEST VER-5A.
  7. At this time, PCM is assumed to be defective. Replace PCM. Perform TEST VER-5A.
  8. Turn ignition off. Visually inspect related connectors and wiring harness for damage. 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