Error 0138 on Nissan: oxygen sensor malfunction - how to fix?

Error code P0138 on cars Nissan - one of the most common problems associated with the engine management system. She signals malfunction of the oxygen sensor circuit (lambda probe), installed after the catalytic converter (bank 1). Unlike the error P0130, which indicates a general malfunction of the lambda probe, P0138 specifically talks about voltage in the sensor circuit exceeds the permissible threshold (usually >1.5 V).

Owners Nissan Qashqai, X-Trail, Juke and other models with gasoline engines HR16DE, MR20DE or QR25DE encounter this error most often. Moreover, it can appear both on a cold and on a warm engine, and is sometimes accompanied by failures during acceleration, increased fuel consumption or unstable operation at idle. In this article we will look at why this occurs. P0138, how to diagnose it correctly and whether it is possible to fix the problem without visiting a service center.

What does P0138 mean on Nissan?

Error P0138 stands for "High Voltage in Oxygen Sensor Circuit (Bank 1, Sensor 2)" - that is high voltage in the second oxygen sensor circuit (installed after the catalyst). Normally, the lambda probe should produce a signal in the range 0.1–0.9 V, but in the event of a malfunction this value may jump to 1.5 V and above.

It is important to understand that bank 1 - this is the side of the engine where it is located first cylinder (usually from the timing side). Sensor 2 — a sensor after the catalyst, responsible for monitoring the efficiency of its operation. If ECU (electronic control unit) detects abnormally high voltage longer 2–3 seconds, it logs an error P0138 and can put the engine into emergency mode.

• 🔧 Main reasons: malfunction of the sensor itself, damage to the wiring, oxidation of the contacts, ground problems or problems with ECU.
• ⚡ Consequences of ignoring: increase in fuel consumption by 10–15%, loss of power, possible damage to the catalyst.
• 🚗 Nissan models where it is most common: Qashqai J10/J11, X-Trail T31/T32, Juke F15, Note E12.

Reasons for error 0138

To effectively eliminate P0138, you need to accurately determine the root cause. Let's consider all possible scenarios, from the most likely to the rare.

1. Malfunction of the oxygen sensor itself (lambda probe). Over time, the sensor wears out: its ceramic element becomes covered with soot, and the internal circuits lose conductivity. Average service life of a lambda probe - 80–100 thousand km, but on Nissan with engines HR16DE And MR20DE they often fail earlier due to bad fuel or oil soot.

2. Problems with wiring or connector. Oxidation of contacts, frayed wires or a short circuit to ground - all this can lead to a false signal. Wires around exhaust manifoldwhere they overheat. On Nissan Qashqai The sensor connection chip often suffers - its contacts become covered with green oxide over time.

3. Sensor heater circuit malfunction. The lambda probe begins to work correctly only after warming up to 300–400°C. If the heater circuit is damaged, the sensor may give incorrect readings, resulting in P0138.

Reason	Probability (%)	Diagnostic method
Lambda probe malfunction	60%	Check with a multimeter, replace with a known good one
Wiring/connector problems	25%	Visual inspection, continuity of circuits
Sensor heater malfunction	10%	Checking the heater resistance (standard: 2–10 ohms)
Ground or ECU problems	5%	Diagnostics with a scanner, checking the power supply of the unit

⚠️ Attention: If the error P0138 appears along with P0130 or P0141, the problem is almost certainly in the sensor itself or its heating circuit. If she is the only one, check wiring and ground.

How to diagnose error P0138 yourself?

For diagnostics you will need multimeter, OBD-II scanner (For example, ELM327) and basic electrical skills. Follow the step by step instructions:

Step 1: Read the errors with the scanner. Connect the adapter to the connector OBD-II (usually located under the steering wheel) and check all saved errors. If in addition P0138 There is P0135 (heater malfunction), the sensor definitely needs to be replaced.

Step 2: Check the voltage at the sensor. Start the engine and warm it up to operating temperature. Connect the multimeter in mode DC 20V to the contacts of the signal wire (usually black or gray) and mass. Normal voltage should fluctuate in the range 0.1–0.9 V. If it's stable >1.2 V - the sensor is faulty.

Read errors with an OBD-II scanner|Check the voltage on the sensor with a multimeter|Inspect the wiring for damage|Check the heater resistance (2–10 ohms)|Ring the circuit for a short circuit-->

Step 3: Check heater resistance. Disconnect the sensor connector and measure the resistance between the heater contacts (usually white and brown wires). Normal value - 2–10 ohms. If the resistance approaches infinity, the heater has burned out.

Step 4: Inspect the wiring. Carefully check the wires from the sensor to ECU for chafing, melting or oxidation. Pay special attention to the area around exhaust manifoldwhere wires often overheat.

How to fix error P0138: step-by-step instructions

The repair method depends on the cause of the problem. Below is an algorithm of actions for each case.

1. Replacing the lambda probe. If the sensor is faulty, it must be replaced. For Nissan Qashqai (engine HR16DE) the original sensor will fit 22690-4M015 or analogues from Bosch (article 0 258 006 537) or NGK (NTK 24317). Average cost - 3 000–6 000 ₽.

Installation:

• 🔧 Disconnect the negative terminal of the battery.
• 🔧 Disconnect the sensor connector.
• 🔧 Using the key on 22 mm Unscrew the old sensor (WD-40 may be needed).
• 🔧 Install a new sensor, connect the connector and battery terminal.

2. Wiring repair. If the problem is in the wires:

• 🔧 Clean the oxidized contacts in the connector (use contact lubricant).
• 🔧 Replace damaged wiring areas using heat shrink tubing.
• 🔧 Check the reliability of the sensor mass (usually screwed to the body next to ECU).

3. ECU check. In rare cases, an error P0138 may be caused by a faulty control unit. If all the previous steps did not help, contact a diagnostician to check ECU for firmware failures or damage to the board.

⚠️ Attention: After replacing the sensor or repairing the wiring be sure to clear errors through a scanner. If the code P0138 appears again - the problem has not been resolved or a new malfunction has crept in.

Is it possible to drive with P0138?

Technically yes, but with reservations. The engine will run, but:

1. Fuel consumption will increase. Without correct data from the second sensor ECU switches to emergency settings, enriching the mixture. Consumption may increase by 1–2 liters per 100 km.

2. Possible failures during overclocking. Incorrect fuel adjustment leads to twitching or dull response to the gas pedal.

3. Risk of catalyst damage. If you ignore the error for a long time, a faulty sensor can lead to overheating or clogging of the catalyst, and replacing it will cost 30 000–80 000 ₽.

4. Failure to pass inspection. There is an error P0138 in memory ECU - a reason for refusing to issue a diagnostic card.

What happens if you turn off the second lambda probe?

Disabling the second sensor (after the catalyst) will lead to a permanent error P0138 or P0141, but the engine will run. However, this is fraught with:

- increase in fuel consumption by 10–15%;

- the risk of damage to the catalyst due to incorrect mixture correction;

- problems when passing technical inspection.

On some models (for example, Nissan X-Trail T32) long driving with the sensor disabled can lead to flashing ECU in emergency mode with speed limit to 3,000 rpm.

Preventing error P0138 on Nissan

To avoid reappearance P0138, follow these guidelines:

• ⛽ Refuel at proven gas stations. Poor fuel with high sulfur content or additives accelerates the wear of lambda probes.
• 🔧 Check the condition of the wiring regularly. Once every 20,000 km inspect the harnesses near the exhaust manifold.
• 🚗 Don't ignore fuel system errors. Codes P0171 (lean mixture) or P0300 (misfire) can indirectly affect the operation of oxygen sensors.
• 🔥 Monitor the condition of the catalyst. A clogged catalyst creates excess pressure in the outlet, which leads to overheating of the sensors.

If your Nissan often used in urban cycle (short trips, traffic jams), lambda probes wear out faster due to insufficient heating. In this case, it is recommended once every 1–2 months drive through 20–30 km on the highway at speed 80–100 km/hso that the sensors clean themselves.

FAQ: Frequently asked questions about error P0138

Is it possible to reset the P0138 code without repair?

Yes, you can erase the error through the scanner, but it will return if the problem is not resolved. Some owners Nissan temporarily turn off the second lambda probe, but this is fraught with increased fuel consumption and the risk of damage to the catalyst.

How much does it cost to replace a lambda probe on a Nissan?

The cost depends on the model and type of sensor:

• Original sensor: 5 000–8 000 ₽.
• Analogue (Bosch, NGK, Denso): 2 500–4 500 ₽.
• Replacement work: 1 000–2 000 ₽ (if the sensor is not stuck).

On Nissan Qashqai J11 with engine MR20DD replacement may be more expensive due to difficult access to the sensor.

Could P0138 be caused by bad fuel?

Yes, but indirectly. Bad fuel leads to soot formation on the sensor, which distorts its readings. If after refueling at an unfamiliar gas station a P0138, try to fill fuel system cleaner (For example, Liqui Moly Injection Reiniger) and drive 50–100 km at high speeds.

What is the difference between P0138 and P0130?

Both errors are related to the second lambda probe (after the catalyst), but:

• P0130 — low signal (voltage <0.1 V).
• P0138 — high signal (voltage >1.5 V).

P0130 more often caused open circuit or severe contamination of the sensor, and P0138 — short circuit or heater malfunction.

Do I need to change both lambda probes if only the second one is faulty?

No, it is enough to replace only the faulty sensor. However, if the vehicle mileage exceeds 150,000 km, it is recommended to check the first sensor (before the catalyst), since its resource is also coming to an end.