Trouble code P2138 on Nissan: faulty throttle body or sensors?

Fault code P2138 on cars Nissan - one of the most common problems associated with the engine management system. This error indicates an inconsistency in the signals from the throttle position sensors (TPS) or a malfunction in their power supply circuit. Most often it appears on models Qashqai J10/J11, X-Trail T31/T32, Juke F15 And Note E12, but can also occur on other cars with an electronic gas pedal.

Owners are faced with P2138 after replacing the throttle assembly, cleaning the valve or when contacts in the connectors are worn. Symptoms range from floating speed and jerking during acceleration to the engine completely going into emergency mode. In this article we will analyze all possible reasons, diagnostic methods (including testing with a multimeter), and step-by-step repair instructions - from throttle calibration to sensor replacement.

What does error code P2138 mean on Nissan?

Code P2138 stands for "Throttle/Pedal Position Sensor/Switch 'D'/E Circuit Low Input" - low signal from the throttle position sensor (or accelerator pedal) in the circuit D or E. In modern Nissan with the system Drive-by-Wire (electronic gas pedal) two sensors are used on the throttle assembly:

• 🔹 TPS1 - main sensor (circuit A And B);
• 🔹 TPS2 - backup sensor (circuits C, D, E).

Error P2138 indicates a problem in the second sensor (or its circuits). The engine ECU compares the signals from both sensors, and if the data diverges by more than 10–15%, a malfunction is detected. Important: on some models (for example, Nissan Almera N16) the code may indicate a malfunction of the gas pedal sensor, not the throttle valve.

Symptoms of the error P2138:

• 🚗 Lights up Check Engine;
• 📉 Floating idle speed (500–1500 rpm);
• 🚘 Jerks during acceleration or slow response to the gas pedal;
• 🔧 Engine transition to emergency mode (limiting speed to 2000–3000).

The main causes of error P2138

Reasons for the appearance P2138 several, and they are divided into mechanical (wear, contamination) and electric (breaks, short circuits). Below is a complete list with clarifications for specific models Nissan.

Reason	How it manifests itself	Models where it is more common
Worn or dirty throttle valve	Floating speed, jerking during acceleration	Qashqai J10, X-Trail T31, Note E12
TPS2 sensor malfunction (or open circuit)	The error appears immediately after startup	Juke F15, Almera N16
Oxidation of contacts in the throttle body connector	The error disappears after cleaning the contacts	Tiida C11, Sentra B17
Incorrect calibration after replacing throttle	Error appears after repair	All models with Drive-by-Wire
Short circuit in wiring harness	The error is accompanied by other codes (P0120, P0220)	Pathfinder R51, Murano Z51

Most common reason — contamination of the throttle valve or wear of its mechanism. On cars with a mileage of more than 100 thousand km, carbon deposits on the damper and in the bypass channel lead to incorrect operation of the sensors. The second most common problem is oxidation of the contacts in the throttle assembly connector, especially after washing the engine or in high humidity conditions.

How to Diagnose Code P2138?

Diagnostics P2138 requires a systematic approach. Start with a visual inspection, then move on to checking the electrical circuits and only change parts last. Below are step-by-step instructions.

1. Visual inspection of the throttle assembly

Remove the air duct and inspect the throttle valve:

• 🔍 Check availability coal deposits on the damper and walls;
• 🔌 Inspect the connector for oxidation or damage;
• 🛠️ Make sure the flap is moving smoothly (no jamming).

2. Checking sensors with a multimeter

To diagnose TPS sensors you will need a multimeter. Connect it in voltage measurement mode (DC 20V) to the contacts of the throttle assembly connector:

• 🔋 Sensor power supply: between contacts 1 (VCC) And 6 (weight) there must be 5 V;
• 📊 TPS1 signal: between 2 (output) And 6 (weight) - from 0.3 V (flap closed) until 4.5 V (open);
• 📉 TPS2 signal: between 3 (output) And 6 (weight) - similar to TPS1, but with reverse polarity.

If the voltage is TPS2 below 0.1 V or missing - the sensor is faulty. Also check the resistance between the contacts 3 And 6: it should change smoothly when the damper moves (from 1 kOhm to 5 kOhm).

Disconnect the throttle body connector|

Set the multimeter to DC 20V mode |

Check power supply (5V between pins 1 and 6)|

Measure the TPS2 signal (between pins 3 and 6)|

Check the smoothness of the change in resistance when the damper moves -->

3. Checking circuits for open or short circuit

If the sensors are working, but the error remains, check the wires:

• 🔌 Disconnect the throttle unit and ECU connector;
• 📏 Ring the circuits between the contacts 3 (TPS2) and the corresponding pin on the ECU (see diagram for your model);
• 🔍 Make sure that the insulation resistance between the wires is at least 1 MOhm.

⚠️ Attention: On Nissan Qashqai J11 And X-Trail T32 open circuit TPS2 often occurs in the harness under the hood and the attachment point to the side member. Check the wires for chafing!

How to resolve error P2138?

The method of repair depends on the cause. Below are step-by-step instructions for each case.

1. Cleaning the throttle body

If the valve is dirty, it needs to be cleaned without removing (so as not to confuse ECU adaptation):

1. Remove the air duct and open access to the throttle;
2. Apply carburetor cleaner (LIQUI MOLY Pro-Line or CRC Throttle Body Cleaner) to the damper and bypass channel;
3. Wipe with a soft cloth (do not use brushes!);
4. Repeat 2-3 times until the carbon deposit disappears.

After cleaning necessarily Perform throttle calibration (see next section).

2. Throttle calibration

On most Nissan calibration is performed via CONSULT-III or scanner ELM327 with the program Nissan DataScan. Alternative method (for models before 2015):

1. Turn on the ignition (without starting the engine);
2. Wait 3 seconds;
3. Fully press and release the gas pedal 5 times;
4. Wait 7 seconds;
5. Press the gas pedal all the way down and hold it for 20 seconds until the light flashes Check Engine;
6. Release the pedal and turn off the ignition.

⚠️ Attention: On Nissan Juke F15 And Qashqai J11 After 2015, manual calibration does not work - diagnostic equipment is required!

3. Replacing the TPS2 sensor or throttle assembly

If the sensor is faulty, it can be replaced separately (on some models) or the entire throttle assembly. Article numbers for popular models:

• 🔧 Nissan Qashqai J10 (2.0 MR20DE): throttle assembly - 22680-4M000;
• 🔧 X-Trail T31 (2.5 QR25DE): TPS sensor - 22680-5M500;
• 🔧 Juke F15 (1.6 HR16DE): assembly - 22680-BM400.

After replacement necessarily perform calibration!

Common mistakes during repairs

Many owners Nissan make the same mistakes when eliminating P2138, which causes the code to reappear. That's what can't do:

• 🚫 Clean the throttle body metal brushes — this damages the coating and accelerates the accumulation of soot;
• 🚫 Change sensors one at a time - if it fails TPS2, will soon refuse and TPS1 (it is better to change the assembly);
• 🚫 Ignore calibration after cleaning or replacing, this is guaranteed to return an error;
• 🚫 Try to “reset” the error disconnecting the battery terminal - this will not eliminate the cause, but only temporarily hides the symptom.

Another common mistake is using non-original sensors. On Nissan even a slight deviation in the characteristics of the sensor leads to a divergence of signals and the recurrence of P2138. Buy only original spare parts or proven analogues (Hitachi, Denso).

Why does the error return after replacing the throttle?

On some models (for example, Nissan Note E12) The ECU “remembers” the parameters of the old throttle assembly. If the new component has different characteristics (even within tolerance), the ECU records the discrepancy and issues P2138 again. The solution is to flash the ECU or install a unit with identical parameters.

Preventing error P2138

To avoid reappearance P2138, follow these guidelines:

• 🔧 Clean the throttle body every 50–60 thousand km (use only specialized cleaners);
• 🔌 Once a year, treat the connector contacts spray for electronics (For example, WD-40 Specialist Contact Cleaner);
• 🛢️ Use quality fuel — cheap gasoline accelerates the formation of soot;
• 🔋 Monitor the voltage of the on-board network - drawdowns below 11.5 V may cause sensor malfunctions.

For cars with mileage of more than 150 thousand km, it is recommended preventive replacement of the throttle assembly - even if the error has not yet appeared. The cost of the original unit for Qashqai J10 or X-Trail T31 is about 8–12 thousand rubles, which is cheaper than repairing the consequences (for example, malfunction of ignition coils due to unstable speed).

FAQ: Frequently asked questions about error P2138

Is it possible to drive with error code P2138?

For a short time - yes, but the engine will operate in emergency mode (limited speed, jerking). Driving for a long time with this error leads to:

• 🔥 Overheating of the catalyst;
• 🔧 Accelerated wear of spark plugs and ignition coils;
• 🛢️ Increased fuel consumption (up to 20%).

It is recommended to resolve the problem within 1–2 weeks.

Why does P2138 appear after washing the engine?

Water enters the throttle body or ECU connector, causing corrosion of the contacts. To avoid this:

• 🚿 Cover the throttle assembly with polyethylene before washing;
• 🔌 After washing, blow the connectors with compressed air;
• 🔋 Process contacts dielectric grease.

How to distinguish a TPS2 malfunction from problems with the gas pedal?

If the error P2138 accompanied by code P2122 or P2127, the problem is in the accelerator pedal sensor. If only P2138 — the throttle assembly is at fault. Also, if the gas pedal is faulty:

• 🚗 The engine does not respond to pedal pressure;
• 📉 The turnover automatically drops to 0;
• 🔧 The error appears when driving, not at idle.

How much does it cost to repair error P2138 in the service?

The cost depends on the reason:

• 🔧 Throttle cleaning: 1,500–3,000 ₽;
• 🔧 Replacement of TPS sensor: 3,000–6,000 ₽ (including labor);
• 🔧 Replacement of the throttle assembly: 10,000–18,000 ₽;
• 🔧 Diagnostics + ECU firmware: 5,000–10,000 ₽.

On Nissan Juke F15 And Qashqai J11 after 2015, replacing the throttle without flashing the ECU may not eliminate the error - this increases the cost of repairs to 20-25 thousand rubles.

Is it possible to replace the throttle assembly yourself?

Yes, but you will need:

1. Remove the air duct and disconnect the connectors;
2. Unscrew the 4 throttle mounting bolts;
3. Install the new unit and connect the connectors;
4. Perform calibration (required!).

Difficulty: 5/10 (a minimum set of tools and a diagnostic scanner are required).