Nissan Error P0138: Oxygen Sensor Voltage High - What to Do?

Error code P0138 on the dashboard Nissan indicates a problem with oxygen sensor (lambda probe) in the first row, bank 1 - its voltage exceeds the permissible threshold (usually higher 1.35 V). This malfunction can lead to increased fuel consumption, unstable engine operation and even damage to the catalyst. Owners Qashqai, X-Trail And Juke encounter it especially often due to the design features of the exhaust system.

Unlike the error P0130 (incorrect sensor signal), P0138 points specifically to overvoltage, which is usually associated with an open heating circuit, short circuit or contamination of the sensitive element. This error cannot be ignored: long-term driving with a faulty lambda probe can damage the catalytic converter, the repair of which will cost 30 000–80 000 ₽.

What does P0138 mean on Nissan?

Code P0138 stands for "O2 Sensor Circuit High Voltage (Bank 1, Sensor 2)" - high voltage in the oxygen sensor circuit located after the catalyst (second sensor in a row). Unlike the first lambda probe (control), this sensor diagnostic: It controls the efficiency of the catalyst.

The normal voltage of a working sensor fluctuates within 0.1–0.9 V. If the ECU records a value higher 1.35 V longer 10 seconds, lights up Check Engine, and an error is logged. The reasons can be either electrical (break, short circuit) or mechanical (pollution, wear).

• 🔋 Electrical reasons: open heating circuit, short circuit to ground or +12V, damaged wiring.
• 🛢️ Mechanical reasons: sensor contamination with oil soot, antifreeze or fuel additives.
• 🔥 Problems with the catalyst: it is destroyed or clogged, causing the sensor to record false data.
• ⚡ ECU malfunction: Rarely, but the control unit may misinterpret the signal.

On Nissan Qashqai (J10, J11) And X-Trail (T31, T32) error P0138 often accompanied P0420 (low catalyst efficiency). This is due to the fact that the ECU uses data from the second sensor to adjust the fuel mixture. If the sensor is lying, the engine starts running on a rich mixture, which accelerates wear of the catalyst.

Symptoms of error code P0138 on Nissan

Error P0138 may manifest itself differently depending on the model and degree of malfunction. At the initial stage, the driver may not notice any changes other than the light Check Engine. But over time, the symptoms become more obvious:

• ⚠️ Floating speed at idle speed (especially on a cold engine).
• 🛢️ Increased fuel consumption on 10–20% due to incorrect fuel mixture.
• 🚗 Jerks during acceleration, power failures (the ECU goes into emergency mode).
• 💨 Smell of sulfur or rotten eggs from the exhaust pipe (a sign of an over-rich mixture).
• 🔥 Catalyst overheating (you can hear a crackling noise under the car after stopping).

On Nissan Juke (F15) And Note (E12) error P0138 often leads to freezing speed at the mark 1500–2000 rpm after releasing the gas pedal. This is due to the fact that the ECU tries to compensate for false sensor data by increasing the fuel supply.

⚠️ Attention! If together with P0138 an error appeared P0172 (rich mixture), immediately check the sensor for a short circuit. Long-term driving in this mode can lead to water hammer and damage to the piston group.

Causes of error P0138

To pinpoint the cause P0138, you need to analyze the conditions under which the error occurred. For example, if the code only appears when the engine is cold, the problem is likely in the sensor heater. If the error is permanent, the sensor itself or the wiring is to blame.

On Nissan Qashqai J11 with engines HR16DE And MR20DD error P0138 often occurs due to poor contact in the sensor connector. Moisture or oxidation of contacts leads to periodic failures. Could also be the culprit ground wire, which on these models is attached to the body next to the exhaust and rusts over time.

How to diagnose P0138 yourself

For diagnostics you will need multimeter, OBD-II scanner (For example, ELM327) and oscilloscope (optional). If you don’t have an oscilloscope, you can use a multimeter in voltage measurement mode.

Check the sensor heating circuit for open circuit (resistance 2–10 ohms)

Measure the voltage on the signal wire (should be 0.1–0.9 V)

Check the integrity of the wiring from the sensor to the ECU

Inspect the sensor connector for oxidation or moisture.

Remove the sensor and check for contamination

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Step 1: Check the heating circuit

Disconnect the sensor connector and measure the resistance between the heating contacts (usually 3 and 4 on the connector). Normal value for most sensors Nissan — 3–8 ohms. If the resistance tends to infinity - a break, if 0 ohm - short circuit.

Цвета проводов подогрева на Nissan:
- Qashqai J10/J11: белый и чёрный
- X-Trail T31: серый и чёрный
- Juke F15: красный и чёрный

Step 2: Check the signal wire

Connect the multimeter in voltmeter mode between the signal wire (usually 1 on the connector) and ground. With the engine running, the voltage should fluctuate within the range 0.1–0.9 V. If it's stable 1.3–1.5 V — the sensor is faulty or there is a short circuit to positive.

Step 3. Visual inspection of the sensor

Remove the sensor and inspect its tip:

- Black plaque - over-enriched mixture or oil zhor.

- White coating — antifreeze enters the combustion chamber (cylinder head gasket is broken).

- Brown plaque — fuel additives or additives.

⚠️ Attention! On Nissan with V6 engines (VQ35DE, VQ25DD) oxygen sensors have unique pinout. Do not confuse them with sensors from 4-cylinder engines - this will lead to damage to the ECU!

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

The repair method depends on the cause of the problem. In most cases it is enough replace the sensor or clean contacts. But if the problem is in the wiring or the ECU, more serious repairs will be required.

1. Replacing the oxygen sensor

On Nissan Sensors with article numbers are used:

- 22690-4M000 (for Qashqai J10, X-Trail T31)

- 22690-4M010 (for Juke F15, Note E12)

- 22690-AL500 (for Almera N16, Tiida C11)

To replace:

1. Disconnect the negative terminal of the battery.

2. Disconnect the sensor connector.

3. Key on 22 mm unscrew the sensor (pre-treat the thread WD-40).

4. Install the new sensor, lubricating the threads with graphite lubricant.

5. Connect the connector and reset the errors using the scanner.

2. Wiring repair

If the problem is an open or short circuit:

- Find the location of the damage (most often the commutator wire is frayed).

- Strip and solder the wires, insulating them with heat shrink tubing.

- Check the integrity of the shielding braid (its absence may cause interference).

3. Cleaning the sensor (temporary solution)

If the sensor is dirty, you can try cleaning it:

1. Immerse the tip in phosphoric acid on 10–15 minutes.

2. Rinse with water and dry.

3. Reinstall and check operation.

⚠️ This method only works with light contamination. A badly worn sensor cannot be cleaned.

Common repair mistakes and how to avoid them

Many owners Nissan make typical mistakes that lead to reoccurrence P0138 or damage to other systems. That's what can't do:

• 🔧 Use universal sensors instead of the original ones. For example, a sensor from Toyota may physically fit, but the ECU Nissan will misinterpret its signal.
• 🔥 Use force when unscrewing the sensor. The threads in the manifold are soft and easy to strip. If the sensor does not work, warm up the collector with a hairdryer.
• ⚡ Ignore P0420. If she appears with P0138, first check the catalyst - perhaps the sensor is working, and the problem is a clogged catalyst.
• 🛢️ Use thread sealant. It can get on the sensitive element of the sensor and damage it. Only graphite lubricant is allowed.

On Nissan Pathfinder R51 And Murano Z50 a situation often occurs when, after replacing the sensor, an error occurs P0138 returns in 100–200 km. The reason is poor grounding of the ECU. On these models, the mass of the control unit is attached to the body under the dashboard. Over time, the contact oxidizes and the ECU begins to fail. The solution is to strip and duplicate the ground with a separate wire.

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

Prices for diagnostics and repair of errors P0138 vary depending on region and vehicle model. On average:

Do-it-yourself repairs are more profitable, but require time and tools. For example, replacing a sensor with Nissan Qashqai J11 takes about 30–40 minutes, if there are no problems with unscrewing. The service will charge you for this work 1 500–2 500 ₽ plus the cost of spare parts.

If the problem is in the catalyst, then the service often suggests installing decoy instead of a new catalyst. It's cheaper (3 000–5 000 ₽), but is fraught with problems during maintenance. Alternative - universal catalyst (from 8 000 ₽), which will last 50,000–80,000 km.

FAQ: Frequently asked questions about error code P0138 on Nissan

1. Включите зажигание (не запуская двигатель).
2. Нажмите педаль газа до упора и удерживайте 10 секунд.
3. Отпустите педаль, затем нажмите её снова на 5 секунд.
4. Заглушите автомобиль и запустите снова.