Rick's Free Auto Repair Advice

When to replace an oxygen sensor

When to replace an oxygen sensor

If you have an oxygen sensor code, don’t automatically assume the sensor is bad, In fact, the vast majority of oxygen sensors replaced by DIYers are actually perfectly fine. Before you waste money on a new oxygen sensor, you must understand that just because the words oxygen and sensor are mentioned in the trouble code does NOT automatically mean the sensor is bad.

Not all oxygen sensor codes require a new oxygen sensor

I’ve listed all the generic oxygen sensor related trouble codes. I’m going to break down what they actually mean and which tests you should perform before replacing the sensor.

Let’s start with oxygen sensor location definitions

Bank refers to the location of the sensor on “V” style engine. Bank 1 is the side of the engine that has cylinder #1, while bank #2 is the opposite side.

Sensor 1, Sensor 2 Sensor 3 refer to whether the sensor is located in front of the catalytic converter (sensor 1), after the catalytic converter (sensor 2) or after a secondary catalytic converter (sensor 3).

Understanding oxygen sensor heaters

An oxygen sensor must reach a certain temperature before it can provide accurate readings. Car makers learned long ago that an oxygen sensor can be heated to the right temperature with hot exhaust gas but drop below that minimum temperature when the engine is idling in cold weather. To correct that issue, they began using oxygen sensors with a built-in heater. The heater keeps the sensing elements at the correct temperature at all times.

An oxygen sensor heater runs off of battery voltage and the circuit is always fused. In some cases, the wiring harness from the oxygen sensor is spliced at one location.

So, if you see any of the oxygen sensor related trouble codes shown below, do NOT automatically replace an oxygen sensor. Start by checking the oxygen sensor heater fuse and check for heater power and ground right at the oxygen sensor electrical connector. You may need a wiring diagram to determine which oxygen sensor terminals to check.

How the ECM checks the oxygen sensor heater

When you start the engine, the ECM knowns the oxygen sensor is receiving power to the heater by monitoring the heater ground voltage. If it sees a large voltage drop, it knows the heater is getting power. If the voltage drop is higher or lower than expected, it knows there’s a problem. The issue can be increased resistance in the power feed to the heater (usually caused by corrosion in the connection or splice). If there’s no voltage drop, the ECM assumes there’s an open in the circuit. Either way, a heater low or high voltage is something that must be diagnosed before you automatically replace the sensor.

If you measure battery voltage and good ground at the oxygen sensor in question and you have any of these trouble codes, THEN you can assume the heater has failed and you must replace the oxygen sensor.

P0030 Heated Oxygen Sensor (H02S) Heater Control Circuit Bank 1 Sensor 1
P0031 Heated Oxygen Sensor (HO2S) Heater Circuit Low Voltage Bank 1 Sensor 1
P0032 Heated Oxygen Sensor (HO2S) Heater Circuit High Voltage Bank 1 Sensor 1
P0036 Heated Oxygen Sensor (HO2S) Heater Control Circuit Bank 1 Sensor 2
P0037 Heated Oxygen Sensor (HO2S) Heater Circuit Low Voltage Bank 1 Sensor 2
P0038 Heated Oxygen Sensor (HO2S) Heater Circuit High Voltage Bank 1 Sensor 2
P0042 HO2S Heater Control Circuit (Bank 1, Sensor 3)
P0043 HO2S Heater Control Circuit Low (Bank 1, Sensor 3)
P0044 HO2S Heater Control Circuit High (Bank 1, Sensor 3)
P0050 Heated Oxygen Sensor (HO2S) Heater Circuit Bank 2 Sensor 1
P0051 Heated Oxygen Sensor (HO2S) Heater Circuit Low Voltage Bank 2 Sensor 1
P0052 Heated Oxygen Sensor (HO2S) Heater Circuit High Voltage Bank 2 Sensor 1
P0053 HO2S Heater Resistance Bank 1 Sensor 1 (PCM)
P0054 HO2S Heater Resistance Bank 1 Sensor 2 (PCM)
P0055 HO2S Heater Resistance Bank 1 Sensor 3 (PCM)
P0056 Heated Oxygen Sensor (HO2S) Heater Circuit Bank 2 Sensor 2
P0057 Heated Oxygen Sensor (HO2S) Heater Circuit Low Voltage Bank 2 Sensor 2
P0058 Heated Oxygen Sensor (HO2S) Heater Circuit High Voltage Bank 2 Sensor 2
P0059 HO2S Heater Resistance (Bank 2, Sensor 1)
P0060 HO2S Heater Resistance (Bank 2, Sensor 2)
P0061 HO2S Heater Resistance (Bank 2, Sensor 3)
P0062 HO2S Heater Control Circuit (Bank 2, Sensor 3)
P0063 HO2S Heater Control Circuit Low (Bank 2, Sensor 3)
P0135 O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)

Understand oxygen sensor circuit trouble codes

This is the next big area of misunderstanding for DIYers

The codes below tell you what the ECM is seeing. For example, a P0130 means the ECM sees a circuit malfunction. Does the definition say, “oxygen sensor is bad, replace it?” No. It says the circuit is bad. That could mean there’s a problem with the wiring harness, the connector or the sensor itself. If you automatically replace the sensor without checking the circuit, you could be wasting your time and money.

How does the ECM know the circuit has a problem?

The ECM sends a reference voltage to the oxygen sensor and expects to see a return voltage that’s within a certain range. If it doesn’t see that return voltage, it’ll set a circuit code. It’s up to you to check for the correct reference voltage at the oxygen sensor connector before replacing an oxygen sensor.

What do the other oxygen sensor codes mean?

O2 Sensor Circuit Malfunction: check for reference voltage and good return at the oxygen sensor connector

O2 Sensor Circuit Low Voltage: Check for corrosion at the oxygen sensor connector

O2 Sensor Circuit Slow Response: Check for an exhaust leak that’s letting outside air into the exhaust stream

P0130 O2 Sensor Circuit Malfunction (Bank 1 Sensor 1)
P0131 O2 Sensor Circuit Low Voltage (Bank 1 Sensor 1)
P0132 O2 Sensor Circuit High Voltage (Bank 1 Sensor 1)
P0133 O2 Sensor Circuit Slow Response (Bank 1 Sensor 1)
P0134 O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 1)
P0136 O2 Sensor Circuit Malfunction (Bank 1 Sensor 2)
P0137 O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)
P0138 O2 Sensor Circuit High Voltage (Bank 1 Sensor 2)
P0139 O2 Sensor Circuit Slow Response (Bank 1 Sensor 2)
P0140 O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 2)
P0141 O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)
P0142 O2 Sensor Circuit Malfunction (Bank 1 Sensor 3)
P0143 O2 Sensor Circuit Low Voltage (Bank 1 Sensor 3)
P0144 O2 Sensor Circuit High Voltage (Bank 1 Sensor 3)
P0145 O2 Sensor Circuit Slow Response (Bank 1 Sensor 3)
P0146 O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 3)
P0147 O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 3)
P0150 O2 Sensor Circuit Malfunction (Bank 2 Sensor 1)
P0151 O2 Sensor Circuit Low Voltage (Bank 2 Sensor 1)
P0152 O2 Sensor Circuit High Voltage (Bank 2 Sensor 1)
P0153 O2 Sensor Circuit Slow Response (Bank 2 Sensor 1)
P0154 O2 Sensor Circuit No Activity Detected (Bank 2 Sensor 1)
P0155 O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)
P0156 O2 Sensor Circuit 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)
P0161 O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 2)
P0162 O2 Sensor Circuit Malfunction (Bank 2 Sensor 3)
P0163 O2 Sensor Circuit Low Voltage (Bank 2 Sensor 3)
P0164 O2 Sensor Circuit High Voltage (Bank 2 Sensor 3)
P0165 O2 Sensor Circuit Slow Response (Bank 2 Sensor 3)
P0166 O2 Sensor Circuit No Activity Detected (Bank 2 Sensor 3)
P0167 O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 3)

If you’ve checked all the voltages and have determined you have to replace an oxygen sensor, here’s how to do it.

There are two types of oxygen sensor mounting

Flange mount and screw in. For flange mount sensors, you just need rust penetrant and a socket set. Soak the nuts and then remove the. Pull out the oxygen sensor and replace

screw in oxygen sensor

Screw in oxygen sensor

Flange mount oxygen sensor

Flange mount oxygen sensor

Tools needed to replace an oxygen sensor that screws in

Buy or rent a set of oxygen sensor sockets.

Spray the threads with plenty of rust penetrant before trying to remove and oxygen sensor or you will break it.

Then slip the socket over the sensor and unscrew it.

oxygen sensor sockets

image showing how to use an oxygen sensor socket to replace an oxygen sensor

©, 2019 Rick Muscoplat

 

 

Posted on by Rick Muscoplat



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