Fault code P1778 - one of the most common problems in cars Nissan with automatic transmission, especially in models Qashqai, X-Trail And Pathfinder. This error is due to incorrect operation Torque Converter Lockup Solenoid (TCC), which leads to jerking, slipping or even complete loss of traction. Unlike other codes, P1778 often appears when cold or under hard acceleration., which complicates its diagnosis.

Owners Nissan This error is often confused with problems with the gearbox or clutch, but in fact its causes can be either mechanical (wear of parts) or electronic (faulty wiring or control unit). In this article we will look at:

  • 🔍 What exactly does P1778 mean? and how it manifests itself in practice
  • 🛠️ Step-by-step diagnostics (including checking solenoid and wiring)
  • 💰 Repair cost depending on the reason (from 1,500 to 30,000 ₽)
  • ⚠️ What happens if you ignore the error (spoiler: risk of automatic transmission destruction)

What is error P1778 and how does it manifest itself?

Code P1778 stands for Torque Converter Clutch Solenoid Performance — malfunction of the torque converter lock-up solenoid. This solenoid is responsible for smoothly turning on/off the torque converter lock-up, which reduces fuel consumption and improves acceleration dynamics. When it fails, Nissan can:

  • 🚗 Jerky when changing gears (especially from 1st to 2nd)
  • 🔥 Overheat the transmission fluid (burning smell from under the hood)
  • 🛑 Suddenly lose traction at speed (as if the gear is “flying out”)
  • ⚡ The lamp lights up Check Engine with code P1778 or P0740 (related error code)

In practice, the error most often occurs in two scenarios:

  1. In the cold — the solenoid does not have time to warm up, and the torque converter locking is triggered with a delay.
  2. When accelerating hard — increased load leads to clutch slipping.
⚠️ Attention: If the code appears along with P1778 P0730 (incorrect gear ratio), this may indicate mechanical wear of the torque converter clutch. In this case, the entire assembly will need to be replaced, not just the solenoid.
📊 How often do you get error P1778?
  • Only when cold
  • When accelerating hard
  • Check Engine Light Is Constantly On
  • Other

The main causes of error P1778 on Nissan

The reasons are divided into electronic (problems with wiring or control unit) and mechanical (wear of parts). Below is a complete list with the likelihood of occurrence:

Reason Probability, % Repair cost, ₽
TCC solenoid malfunction (jammed or broken winding) 60% 3 000–8 000
Contaminated transmission fluid (ATF) 20% 1 500–4 000
Problems with the wiring or solenoid connector 10% 500–2 000
Malfunction of the automatic transmission control unit (TCM) 5% 15 000–30 000
Mechanical wear of the torque converter clutch 5% 25 000–50 000

The most common reason is solenoid failure. He can either jam (mechanical failure), or lose conductivity (winding breakage). The second most common problem is dirty oil, which clogs the valve body channels and interferes with the normal operation of the solenoid.

Less often, the wiring is to blame: oxidation of contacts or broken wires in the solenoid control circuit. In the most severe cases, the automatic transmission control unit (TCM), but this is typical for cars with mileage over 200,000 km.

How to check the solenoid without removing the automatic transmission?

The solenoid can be checked with a multimeter in resistance mode. Normal value for most models Nissan — 10–25 Ohm. If the device shows 0 ohm (short circuit) or OL (break), the solenoid must be replaced. You can also apply voltage to it 12 V — a working solenoid should click.

Step-by-step diagnosis of error P1778

To accurately determine the cause, follow this algorithm:

Read error codes with a scanner (ELM327 or dealer Consult)

Check the level and condition of the transmission fluid

Measure the resistance of the TCC solenoid with a multimeter

Check the wiring from the solenoid to the control module (TCM)

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Step 1: Read codes

Use a diagnostic scanner (eg ELM327 with the program Torque Pro or Nissan DataScan). If there are codes in addition to P1778 P0740 (solenoid circuit malfunction) or P0730 (incorrect gear ratio), this narrows the search.

Step 2: Checking the transmission fluid (ATF)

  • 🔧 Open the hood and find the automatic transmission dipstick (on Qashqai J11 it is to the right of the engine).
  • 📏 The level must be between the marks MIN And MAX on a heated box.
  • 🎨 Liquid color: if it is dark or smells like burning, replacement is required.

Step 3: Checking the Solenoid

The solenoid is located in automatic transmission valve body. To get to it, you need:

  1. Remove the automatic transmission pan (you will need a head on 10 mm).
  2. Disconnect the valve body connector and measure the resistance of the TCC solenoid (standard: 10–25 Ohm).
  3. If the resistance is not normal, the solenoid must be replaced.

Step 4: Check the Wiring

Ring the wires from the solenoid to the control unit (TCM) for open circuit or short circuit. Oxidized contacts in connectors are a common cause of false alarms of P1778.

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If the error remains after replacing the solenoid, reset the automatic transmission adaptations using a dealer scanner (Consult) or program Nissan DataScan. Without this, the control unit may continue to generate false errors.

How to Fix Error P1778: Step-by-Step Instructions

Depending on the cause, repairs can range from a simple fluid change to a complete overhaul of the automatic transmission. Below are solutions for each case.

1. Replacing transmission fluid (ATF)

If the fluid is dirty or smells burning:

  • 🛢️ Buy original liquid Nissan Matic S or Matic J (depending on model).
  • 🔧 Drain the old oil through the plug in the pan (you will need a key for 17 mm).
  • 🔄 Fill in new oil through the filler neck (volume: ~7–9 liters for a complete change).
  • 🔄 Pump the system: start the engine, turn on all gears one by one with a delay of 5 seconds.

2. Replacing the TCC solenoid

If the solenoid is faulty:

  1. Remove the automatic transmission pan and valve body (you will need a head on 10 mm and gasket sealant).
  2. Remove the faulty solenoid (usually marked as TCC or Lock-Up).
  3. Install a new solenoid (part number for Qashqai J11: 31397-31X00 or 31397-31X01).
  4. Reassemble everything in reverse order and reset the errors with the scanner.
⚠️ Attention: When replacing the solenoid, be sure to check the condition of the automatic transmission filter. If it is clogged with wear products, it also needs to be replaced (part number: 31726-31X00).

3. Repair of wiring or connectors

If the problem is in the wiring:

  • 🔍 Locate the solenoid connector (usually white or gray).
  • 🧹 Clean contacts with alcohol or special liquid Contact Cleaner.
  • 🔧 If the wires are damaged, replace them or restore the insulation with heat shrink.

4. Replacing the automatic transmission control unit (TCM)

If faulty TCM:

This is the most expensive repair option. The control unit costs from 15 000 ₽, plus work on replacement and firmware. Before replacing, try:

  • 🔄 Reset automatic transmission settings via scanner.
  • 🔧 Check fuses (e.g. F10 on X-Trail T31).
  • 📡 Reflash the block (sometimes helps with software failures).
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In 80% of cases, the P1778 error is resolved by replacing the solenoid or transmission fluid. If the problem persists, an in-depth diagnosis of the torque converter or TCM is required.

How much does the repair cost and can I do it myself?

The cost of repair depends on the cause and model of the car. Below are estimated prices for Nissan Qashqai J11 (2014–2020):

Type of repair Cost of spare parts, ₽ Cost of work, ₽ Difficulty (1–5)
ATF replacement (partial) 2 000–3 500 1 000–1 500 2
TCC Solenoid Replacement 2 500–5 000 3 000–5 000 4
Cleaning the valve body 500 (liquid + filter) 2 000–3 000 3
Replacing the TCM (control unit) 15 000–25 000 5 000–8 000 5
Torque converter repair 20 000–40 000 10 000–15 000 5

You can deal with it on your own fluid replacement or cleaning contacts. To replace the solenoid, you will need skills in working with automatic transmissions (you need to remove the pan and valve body). Repair TCM or torque converter is best left to professionals.

If you decide to do the repairs yourself, prepare:

  • 🛠️ Set of sockets and keys (10 mm, 17 mm).
  • 🧴 Sealant for the pallet (for example, Loctite 574).
  • 📱 Diagnostic scanner (for resetting errors).
  • 📄 Repair manual for your model (for example, Nissan Qashqai Service Manual).

What happens if you ignore P1778?

Ignoring P1778 results in cascading failures in the transmission. This is what will happen if the cause is not eliminated:

  1. Automatic transmission overheating: A faulty solenoid does not block the torque converter, causing the fluid to overheat, lose its properties and accelerate wear of the clutches.
  2. Torque converter clutch wear: Constant slipping leads to destruction of the clutch linings. Repairs will cost 25 000–50 000 ₽.
  3. Valve block failure: Dirty oil and metal shavings clog the passages, leading to failure of other solenoids.
  4. TCM failure: Constant errors can “burn out” the control unit, and it will have to be replaced.

In the worst case Automatic transmission will need major repairs (from 80 000 ₽), or replacing the box with a contract one (from 150 000 ₽).

⚠️ Attention: On some models Nissan (For example, Pathfinder R51) long-term driving with error P1778 can lead to destruction of the automatic transmission planetary gear. This is a non-repairable failure - the box will need to be replaced.

Frequently asked questions (FAQ)

Is it possible to drive with P1778?

Short term - yes, but no more 1–2 weeks. Long driving will lead to overheating of the automatic transmission and wear of the torque converter. If the error appears only in cold weather, you can postpone repairs until the warm season, but not for long.

Will resetting the error through a scanner help?

No, unless the cause is resolved. Resetting will only temporarily extinguish Check Engine, but the error will return. The exception is a false alarm due to poor contact in the connector.

Which solenoid should I buy: original or analogue?

Original recommended (Nissan 31397-31X00), but high-quality analogues from Ajusa or Febi. Cheap Chinese solenoids often fail after 10–20 thousand km.

Can P1778 appear after changing the automatic transmission oil?

Yes, if:

  • Non-original oil was used (for example, Dexron III instead of Matic S).
  • The automatic transmission adaptation coefficient has not been reset.
  • Dirt got into the box during replacement.

Solution: repeat the oil change with flushing and reset the settings via the scanner.

Where is the TCC solenoid located in Nissan Qashqai?

It is located in automatic transmission valve body, which is attached to the pallet. To get to it, you need:

  1. Remove engine protection.
  2. Unscrew the automatic transmission pan (18 bolts on 10 mm).
  3. Disconnect the valve body connector and remove it.
  4. The TCC solenoid is usually marked or located separately from the others.