Oxygen Sensor Training Guide
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6.0 COMMON OBDII CODES
When an O2 sensor failure occurs, a DTC or diagnostic trouble code is recorded in the ECU and a check engine light appears on the vehicle’s dash. The DTC must be retrieved using a scanning tool. There are generic or standard OBDII codes along with enhanced or OEM specific codes. Below is a list of the more common OBDII codes, along with the possible cause or causes of the code.
| Code | Description | Location | Possible Causes |
|---|---|---|---|
| P0150 | O2 Sensor Circuit Malfunction | Bank 2 Sensor 1 | Broken sensor element. Sensor disconnected. Shorted wiring. Catastrophic failure of sensor due to thermal shock. |
| P0151 | O2 Sensor Circuit Low Voltage | Bank 2 Sensor 1 | Short in wiring between sensor ground and signal wire. Silicone or ethylene glycol poisoning of the air reference electrode. |
| P0152 | O2 Sensor Circuit High Voltage | Bank 2 Sensor 1 | Short in wiring between heater circuit and signal wire. Sensor immersed in water. Silicone or ethylene glycol poisoning of the sensing electrode. |
| P0153 | O2 Sensor Circuit Slow Response | Bank 2 Sensor 1 | Sensor electrode protective coated with carbon. Silicone poisoning. Ethylene glycol poisoning. Failed sensor heater. Heater circuit fuse. |
| P0154 | O2 Sensor Circuit No Activity Detected | Bank 2 Sensor 1 | Short in wiring between sensor ground and signal wire. Silicone or ethylene glycol poisoning of the air reference electrode. |
| P0155 | O2 Sensor Heater Circuit Malfunction | Bank 2 Sensor 1 | Sensor heater shorted or open. Replacement sensor installed with incorrect heater current values. Open or shorted electrical connections. Heater circuit fuse. |
| P0156 | O2 Sensor Circuit Sensor Malfunction | Bank 2 Sensor 2 | Broken sensor element. Sensor disconnected. Shorted wiring. Catastrophic failure of sensor due to thermal shock. |
| P0157 | O2 Sensor Circuit Low Voltage | Bank 2 Sensor 2 | Short in wiring between sensor ground and signal wire. Silicone or ethylene glycol poisoning of the air reference electrode. |
| P0158 | O2 Sensor Circuit High Voltage | Bank 2 Sensor 2 | Short in wiring between heater circuit and signal wire. Sensor immersed in water. Silicone or ethylene glycol poisoning of the sensing electrode. |
| P0159 | O2 Sensor Circuit Slow Response | Bank 2 Sensor 2 | Sensor electrode protective coated with carbon. Silicone poisoning. Ethylene glycol poisoning. Failed sensor heater. Heater circuit fuse. |
| P0160 | O2 Sensor Circuit No Activity Detected | Bank 2 Sensor 2 | Short in wiring between sensor ground and signal wire. Silicone or ethylene glycol poisoning of the air reference electrode. |
| P0161 | O2 Sensor Heater Circuit Malfunction | Bank 2 Sensor 2 | Sensor heater shorted or open. Replacement sensor installed with incorrect heater current values. Open or shorted electrical connections. Heater circuit fuse. |
| P0162 | O2 Sensor Circuit Malfunction | Bank 2 Sensor 3 | Broken sensor element. Sensor disconnected. Shorted wiring. Catastrophic failure of sensor due to thermal shock. |
| P0163 | O2 Sensor Circuit Low Voltage | Bank 2 Sensor 3 | Short in wiring between sensor ground and signal wire. Silicone or ethylene glycol poisoning of the air reference electrode. |
| P0164 | O2 Sensor Circuit High Voltage | Bank 2 Sensor 3 | Short in wiring between heater circuit and signal wire. Sensor immersed in water. Silicone or ethylene glycol poisoning of the sensing electrode. |
| P0165 | O2 Sensor Circuit Slow Response | Bank 2 Sensor 3 | Sensor electrode protective coated with carbon. Silicone poisoning. Ethylene glycol poisoning. Failed sensor heater. Heater circuit fuse. |
| P0166 | O2 Sensor Circuit No Activity Detected | Bank 2 Sensor 3 | Short in wiring between sensor ground and signal wire. Silicone or ethylene glycol poisoning of the air reference electrode. |
| P0167 | O2 Sensor Heater Circuit Malfunction | Bank 2 Sensor 3 | Sensor heater shorted or open. Replacement sensor installed with incorrect heater current values. Open or shorted electrical connections. Heater circuit fuse. |
| P0170 | Fuel Trim Malfunction | Bank 1 | Vacuum Leak. Gas in engine oil. Air leaks. Bad O2 Sensor. |
| P0171 | System Too Lean | Bank 1 | Leaking exhaust gasket or vacuum lines. Defective fuel injector(s). Damaged fuel pump. Clogged fuel filter. |
| P0172 | System Too Rich | Bank 1 | Vacuum leak. Fuel pressure or delivery problem. Faulty MAF sensor. |
| P0173 | Fuel Trim Malfunction | Bank 2 | Vacuum Leak. Gas in engine oil. Air leaks. Bad O2 Sensor. |
| P0174 | System Too Lean | Bank 2 | Leaking exhaust gasket or vacuum lines. Defective fuel injector(s). Damaged fuel pump. Clogged fuel filter. |
| P0175 | System Too Rich | Bank 2 | Vacuum Leak. Gas in engine oil. Air leaks. Bad O2 Sensor. |