Bad Spark plugs can indeed cause O2 sensor code. They cause misfiring and as a result, excess oxygen pops up in the system due to fuel not being ignited. This confuses the ECU and causes the O2 sensor to trigger.
A faulty spark plug may very well lead to your demise. Aside from the fact that your engine will malfunction while on the road, a bad spark plug may also cause irrecoverable damage to your engine.
Can Bad Spark Plugs Cause o2 Sensor Code?
Bad spark plugs do cause an O2 sensor code. As alarming as it sounds, spark plugs misfiring means fuel is not ignited in those cylinders. In that case, there will be excess oxygen as it was not consumed by the burning fuel. The catalytic converter will detect this.
Soon after that, the Electronic Control Unit (ECU) will command increased fuel but the excess O2 will remain the same. Hence the ECU will set a code and the engine will enter “limp mode”.
In other words, a bad spark plug confuses your car’s ECU and triggers the O2 sensor code as a result. Although, the type of error shown depends on the car’s design and manufacturing. Moreover, an engine misfire due to spark plugs can cause excessive vibration or lack of power. This also causes the check engine light to illuminate.
O2 Sensor’s Function
The O2 sensor is mounted on the exhaust to allow the engine computer to maintain a certain air-to-fuel ratio. It helps optimize power, fuel efficiency, and pollutants. The information is sent by the fuel and emission system. It is the unit responsible for monitoring the amount of oxygen in the exhaust and comparing it with the oxygen in the air.
Spark Plug’s Function
The spark plug has to ignite the combination of air and fuel set by the ECU inside the combustion chamber. It also makes sure that the engine has enough power to start while transferring heat away from the ignition chamber.
O2 Sensor Codes
A diagnostic problem code or DTC is stored in the ECU when an oxygen sensor fails due to a particular reason. Soon after that, the check engine light turns on. Here is a list of the most common O2 sensor codes to help you familiarize yourself with them.
| Code | Description | Location |
| P0156 | O2 Sensor Circuit Sensor Malfunction | Bank 2 Sensor 2 |
| P0157 | O2 Sensor Circuit Low Voltage | Bank 2 Sensor 2 |
| P0158 | O2 Sensor Circuit High Voltage | Bank 2 Sensor 2 |
| P0159 | O2 Sensor Circuit Slow Response | Bank 2 Sensor 2 |
| P0160 | O2 Sensor Circuit No Activity Detected | Bank 2 Sensor 2 |
What Can Cause a False O2 Sensor Code
There can be several reasons why a false O2 sensor code may pop up. It could be an engine misfire, a leak in the exhaust valve, or a manifold gasket. Besides, a premature O2 sensor failure can cause contamination which can be disastrous.
Other reasons include clogged filters or lines, restricted fuel filters, faulty sensors, etc. Incorrect input from other sensors can also cause the failure of the O2 sensor such as the wrong input of the Mass Air Flow Sensor.
What Codes Can Bad Spark Plugs Cause
Practically, there are no codes that will specifically tell you that your oxygen sensor or related parts have gone bad and need to be replaced. The maximum you can do is to check all the main chains of things that have given rise to your specific error code.
Do Spark Plugs Affect O2 Sensors
While this depends on the model of the car, spark plugs affecting the O2 sensors are a real thing. Not changing the spark plugs according to the owner’s manual can lead to problems. To illustrate this issue, we can take a look at a longer spark that could protrude into the engine’s combustion chamber, causing serious issues.
Besides, a bad spark plug may be responsible for your engine’s misfiring. As a result, you will feel your car vibrating too much or see a lack of power. Such an issue can be detected by the ECU and cause the check engine light to turn on.
Oxygen Sensor Codes Keep Coming Back
Usually, if you see that your oxygen sensor codes keep coming back, it does not necessarily mean that your O2 sensor was at fault. In fact, anything from bad spark plugs to bad wiring can be behind such an issue. Hence it is important to know what the codes mean and their causes to have a better understanding.
| Code | Description | Possible Causes |
|---|---|---|
| P0150 P0156 | O2 Sensor Circuit Malfunction | – Broken sensor element. – Sensor disconnected. – Shorted wiring. – Catastrophic failure of the sensor due to thermal shock. |
| P0151 P0157 P0163 | O2 Sensor Circuit Low Voltage | – Short in the wiring between sensor ground and signal wire. – Silicone or ethylene glycol poisoning of the air reference electrode. |
| P0152 P0158 P0164 | O2 Sensor Circuit High Voltage | – Short in the wiring between heater circuit and signal wire. – Sensor immersed in water. – Silicone or ethylene glycol poisoning of the sensing electrode. |
| P0153 P0159 P0165 | O2 Sensor Circuit Slow Response | – Sensor electrode protective coated with carbon. – Silicone poisoning. – Ethylene glycol poisoning. – Failed sensor heater. – Heater circuit fuse. |
| P0154 P0160 P0166 | O2 Sensor Circuit No Activity Detected | – Short in the wiring between sensor ground and signal wire. – Silicone or ethylene glycol poisoning of the air reference electrode. |
| P0155 P0161 P0167 | O2 Sensor Heater Circuit Malfunction | – Sensor heater shorted or open. – Replacement sensor installed with incorrect heater current values. – Open or short electrical connections. Heater circuit fuse. |
| P0156 P0162 | O2 Sensor Circuit Sensor Malfunction | – Broken sensor element. – Sensor disconnected. – Shorted wiring. – Catastrophic failure of the sensor due to thermal shock. |
Frequently Asked Questions
Can a misfire cause an O2 sensor code?
Theoretically, it is not conceivable. However, an O2 sensor with defects might produce multiple misfires on a single blank. This could be responsible for an O2 sensor code.
Will a bad O2 sensor cause a check engine light?
An O2 sensor measures the unburnt oxygen amount in the car’s exhaust system. A defective O2 sensor can cause the check engine light to illuminate. However, you can continue to drive safely with it.
Conclusion
An oxygen sensor is bound to fail with age as they become contaminated with carbon and sooty deposits. If a bad spark plug is causing the triggering of the O2 sensor code, it needs to be replaced as soon as possible. A defective oxygen sensor will most likely cause damage to the catalytic converter so you must be quick to tend to it.
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