Error P0138 on Nissan: why the Check Engine light comes on and how to fix it

Error code P0138 on cars Nissan - one of the most common problems associated with the engine management system. She points to oxygen sensor circuit high (Bank 1, Sensor 2), which often misleads owners. Many people mistakenly believe that the problem lies solely in the sensor itself, but in practice the reasons can be much more serious - from simple contamination to malfunctions in the fuel system or even the electronic control unit (ECU).

In this article we will look in detail at what exactly the error means. P0138 for different models Nissan (including Qashqai, X-Trail, Juke And Almera), how to correctly diagnose a malfunction without unnecessary expenses for replacing parts, and what steps to take to eliminate it. We will pay special attention typical mistakes made by car owners during repairs, which may cause the code to reappear or make the problem worse.

What does P0138 mean on Nissan?

Code P0138 stands for "High Voltage in Oxygen Sensor Circuit (Bank 1, Sensor 2)". This means that the engine ECU detects overvoltage (usually higher 0.9 V) from the second lambda probe located after the catalytic converter in the exhaust manifold. Unlike the first sensor (Sensor 1), which regulates the fuel mixture, the second serves to monitor the efficiency of the catalyst.

In practice it looks like this:

• 🔴 Check Engine lights up on the dashboard.
• 📉 The engine may be unstable at idle or during acceleration.
• ⚠️ In some cases (especially on Nissan Qashqai J10/J11 And X-Trail T31/T32) the error is accompanied by increased fuel consumption.

It is important to understand that P0138 does not always mean a sensor failure. Often the problem lies in:

• 🔌 Poor contact or broken wiring.
• 🔥 Burnt-out catalyst (especially on runs beyond 150,000 km).
• ⚡ Malfunctions in the sensor power circuit (for example, short to ground).

Reasons for error P0138

To effectively troubleshoot a problem, you need to understand its root. Here are the main reasons why the ECU issues a code P0138:

Reason	Characteristic signs	Nissan models where it is more common
Malfunction of the second oxygen sensor (lambda probe)	Voltage is higher 0.9 V when the engine is warm, physical damage to the sensor	Qashqai J10, X-Trail T31, Note E11
Contamination or destruction of the catalyst	Increased noise from under the bottom, smell of sulfur, errors P0420 or P0430 paired with P0138	Juke F15, Almera N16, Tiida C11
Problems with the sensor wiring or connector	Intermittent error, contact oxidation, wire breaks	Pathfinder R51, Murano Z50
Air leak in the exhaust system	Popping sounds in the muffler, unstable engine operation	Navara D40, NP300
ECU or firmware malfunction	Multiple errors, inappropriate engine behavior	GT-R R35 (rarely), Teana J32

By car Nissan with mileage for 100,000 km the most likely reason is catalyst wear. The fact is that over time, its honeycombs become clogged or destroyed, which leads to a change in the composition of the exhaust gases. The second oxygen sensor detects this as an abnormally high voltage, and the ECU issues P0138.

⚠️ Attention: If together with P0138 errors appear P0130 or P0136, the problem is most likely in the first oxygen sensor (Sensor 1), and not in the second. In this case, the diagnosis must begin with it.

How to diagnose error P0138 yourself?

Before rushing to change the sensor or catalyst, conduct a comprehensive diagnostic. Here is a step-by-step algorithm:

1. Treat errors as a scanner. Make sure there are no associated codes (for example, P0420 - low catalyst efficiency).
2. Check the voltage at the sensor. Connect the multimeter to the signal wire of the second lambda probe (usually black or gray wire). On a warm engine (coolant temperature 80–90°C) the voltage should fluctuate within 0.1–0.9 V. If it is constantly higher 0.9 V — the sensor or circuit is faulty.
3. Inspect the wiring. Check the sensor connector for oxidation, breaks or short circuits. Pay special attention to the wires running near the exhaust manifold - they often melt from high temperatures.
4. Check the catalyst. If possible, remove the sensor and inspect its tip. Black soot or white deposits indicate problems with the fuel mixture or catalyst.

For more accurate diagnosis, you can use oscilloscope or specialized software like Nissan Consult. For example, on Nissan Qashqai J11 with engine MR20DD It is useful to look at real-time graphs of both oxygen sensors. If the signal of the second sensor “freezes” at a high level, the problem lies with it or with the catalyst.

How to check an oxygen sensor without a scanner?

If you do not have diagnostic equipment, you can use the old-fashioned method: disconnect the connector of the second oxygen sensor while the engine is running. If the error P0138 will disappear, and the engine will start running more smoothly - the sensor is faulty. If the error remains, the problem is in the wiring or the ECU.

Step-by-step instructions for resolving error P0138

Depending on the cause, repair methods will vary. Let's consider the most common scenarios.

1. Replacing the second oxygen sensor

If diagnostics show that the sensor is faulty (for example, the voltage is constant 1.0 V or higher), it must be replaced. For Nissan original sensors fit 22690-4M000 (for Qashqai J10) or 22690-4M010 (for X-Trail T32). You can also use analogues from Bosch or NGK.

Replacement instructions:

1. Disconnect the negative terminal of the battery.
2. Find the second oxygen sensor (usually it is located after the catalyst, closer to the resonator).
3. Disconnect the sensor connector.
4. Using the key on 22 mm unscrew the old sensor. Be careful - the thread often sticks!
5. Install the new sensor by first applying a high-temperature lubricant to the threads (for example, Liqui Moly Kupfer-Spray).
6. Connect the connector and check for errors.

⚠️ Attention: On some models Nissan (For example, Juke F15) the sensor may be “stuck” so much that it will have to be drilled out. In this case, be prepared to replace or repair the threads in the manifold.

2. Cleaning or replacing the catalyst

If the problem is in the catalyst, there are two options:

• 🔧 Cleaning. Suitable only for relatively “fresh” catalysts (mileage up to 120,000 km). You can use special liquids (for example, Liqui Moly Pro-Line Katalysator-Reiniger) or ultrasonic cleaning.
• 🔄 Replacement. On used cars 150,000 km the catalyst is usually not recoverable. Original catalyst for Nissan is expensive (from 30 000 ₽), so many install universal or “fake” ones (if the country’s legislation allows this).

On Nissan Almera N16 And Tiida C11 It is often practiced to remove the catalyst with the installation of a flame arrester and flash the ECU under Euro-2. However, this solution has disadvantages:

• ⚠️ Exhaust noise increases.
• ⚠️ An error may appear P0420, if you do not disable the catalyst control in the ECU.

3. Wiring repair

If the problem is a broken or shorted wire, proceed as follows:

1. Test the circuit with a multimeter in resistance test mode.
2. If you find a break, repair the wire using soldering and heat shrink.
3. If the wiring is melted, replace it completely using high-temperature insulation.

Common repair mistakes and how to avoid them

Many car owners, faced with P0138, make the same mistakes, which lead to re-appearance of code or new problems. Here are the most common:

• 🔧 Replacement of sensor without testing. They change the second lambda probe without bothering to check the catalyst or wiring. As a result, the error is returned via 100–200 km.
• 🔥 Ignoring catalyst errors. If together with P0138 There is P0420, but the catalyst is not checked, the new sensor will quickly fail.
• ⚡ Using cheap analogues. Non-original sensors (especially no-name) often give incorrect readings, which leads to errors P0136 or P0138.
• 🛠️ Incorrect installation. For example, insufficient tightening of the sensor or lack of lubrication on the threads leads to air leaks and new errors.

To avoid these problems, follow a simple rule: diagnostics before repair.Even if you are sure that the sensor is at fault, spend 10–15 minutes to check the wiring and catalytic converter. This will save you time and money.

Cost of repairs in service vs. do-it-yourself repair

Prices for fixing errors P0138 vary depending on the reason and vehicle model. Here are the estimated prices for Nissan in Moscow and regions (for 2026):

Type of work	Cost (₽)	Lead time
Diagnostics with a scanner	500–1 500	15–30 minutes
Replacing the second oxygen sensor	1,500–3,000 (labor) + 3,000–8,000 (spare part)	30–60 minutes
Cleaning the catalyst	2 000–5 000	1–2 hours
Replacing the catalyst (original)	20,000–50,000 (spare part) + 3,000–6,000 (labor)	2–4 hours
Catalyst removal + ECU firmware	5 000–15 000	2–3 hours

Do-it-yourself repairs will be cheaper, but require skills. For example, replacing an oxygen sensor with Nissan Qashqai J11 takes about 20 minutes, if the thread is not stuck. But replacing the catalyst or working with wiring may require special tools (for example, oxygen key for sensors or soldering iron for wiring repairs).

If you are not confident in your abilities, it is better to contact the service. This is especially true for ECU firmware - incorrect actions can damage the unit.

FAQ: Frequently asked questions about error code P0138 on Nissan

Is it possible to drive with P0138?

Short term - yes, but not recommended for long term. Long-term driving with a faulty sensor or catalyst can lead to:

• 🔥 Engine overheating due to incorrect fuel mixture.
• 💨 Increased fuel consumption (up to 1–2 l/100 km).
• ⚡ Damage to the catalyst or lambda probes.

If the error appears for the first time, you can go to the service center, but you should not delay repairs.

Why does P0138 appear after replacing the sensor?

This is a typical situation if:

• 🔌 The new sensor is defective or incompatible with your model Nissan.
• 🔥 The catalyst is clogged or destroyed (the new sensor quickly fails).
• ⚡ There is a short circuit or break in the sensor power supply circuit.

Go back to diagnostics - check the catalytic converter and wiring.

How to reset error P0138 after repair?

There are three ways:

1. Use a diagnostic scanner (for example, Launch X431 or ELM327) to reset errors.
2. Disconnect the negative battery terminal at 10–15 minutes (on some models this clears errors).
3. Wait until the ECU resets the error itself after 2–3 cycles start the engine (if the problem is resolved).

If the error appears again, the repair was performed incorrectly.

Can bad fuel cause P0138?

Yes, but indirectly. If you refuel with low-quality gasoline, this can lead to:

• 🔥 Contamination of oxygen sensors (carbon deposits on the tip).
• 💨 Incorrect operation of the catalyst (due to increased sulfur content).

In this case try:

1. Drain the bad fuel and refuel at a trusted gas station.
2. Add fuel system cleaner (such as Liqui Moly Systempflege).
3. Drive by 50–100 km at high speeds (for example, on the highway) to burn through carbon deposits.

Which Nissan models are most susceptible to P0138?

Statistically most often an error P0138 found on:

• Nissan Qashqai J10 (2007–2013) - problems with the catalyst and sensors.
• Nissan X-Trail T31 (2007–2014) - poor sensor wiring.
• Nissan Juke F15 (2010–2019) - frequent problems with the catalyst on runs over 100,000 km.
• Nissan Almera N16 — corrosion of sensor connectors.

On newer models (eg. Qashqai J11 or Ariya) the error is less common due to improved electronics and catalysts.