Common Transmission Error Codes and What They Mean

Modern vehicles use electronic sensors and onboard diagnostics to monitor the condition of the transmission. When something is not operating correctly, the system stores an error code and often switches the vehicle into a protective mode (Called Limp mode ). Understanding what these codes mean can help you recognise issues early and avoid serious gearbox damage.

If you would like to understand how a CVT works before reading the codes below, visit What is a CVT for a clear explanation.

This guide covers the most common transmission codes seen in popular vehicles such as the Suzuki Swift, Nissan, Mitsubishi, Toyota, Honda and many others fitted with a CVT Transmission

1. Low Oil Pressure (P0776, P0840, P0841, P0846 and more)

Low oil pressure inside the transmission is one of the most common reasons for warning lights or limp mode. CVT units rely on hydraulic pressure to control the pulleys and belt. When the pressure drops, the transmission cannot operate correctly.

What causes it:
• Low or deteriorated transmission fluid
• Blocked filters
• Internal pump wear, which is very common
• Valve body pressure loss or sticky valves, also very common
• Worn seals inside the pulleys and clutch drums, which is the most common cause
• Broken primary pulleys, often seen in the Nissan JF011 RE0F10A units

What it means:
The transmission cannot build enough pressure to function safely. Continued driving can cause rapid wear to the belt and pulleys.

If you are unsure about CVT fluid condition or service intervals, see our FAQ page.

2. Stepper Motor Fault (P1777 and P1778)

Many CVT transmissions use a stepper motor to adjust hydraulic pressure and control pulley positions. When the stepper motor fails, the transmission may struggle to change ratios smoothly.

This fault code can also appear when the piston inside the valve body is stuck or sticky, or when the primary pulley is stuck or broken. This issue is very common in the Nissan X-Trail and the Mitsubishi Outlander.

Common in:
• Nissan CVTs built before 2011
• Mitsubishi CVTs
• Other Jatco CVT models

Symptoms:
• Jerking on take-off
• Loss of power
• Stuck in one gear
• Sudden RPM jumps
• Vehicle stuck in limp mode and not responding to throttle input

If you want to understand how CVT pulleys and motors work together, visit What is a CVT.

3. Speed Sensor Fault

Speed sensors measure the rotational speed of components inside the transmission. When a sensor fault code shows up, the ECU cannot calculate the correct ratio or gear.

Most of the time, it is a Mechanical fault in the Transmission ( not the speed sensor )

What it causes:

• Incorrect speed readings
• Harsh shifting or odd ratio changes
• Failure to accelerate normally
• Vehicle stuck in a single gear
  
  

Speed sensor issues should be checked early. Driving with incorrect readings often triggers limp mode. The Warning page explains why this is risky.

4. Oil Pressure Sensor Failure P0776, P0841, P0846

This sensor monitors internal pressure in real time. When it stops sending accurate readings, the transmission may enter fail-safe mode to protect itself.

Can be caused by the same issues as mentioned in!

Typical signs:

• Transmission warning light
• Delayed engagement
• Slipping under load
• Vehicle refusing to change ratios
  
  

Oil pressure faults are serious. You will find useful information about CVT pressure behaviour on our FAQ page.

5. Torque Converter Failure  P1740, P740, P741,P744

The torque converter transfers engine power into the transmission. When it begins to fail, the vehicle may shake, slip or struggle to accelerate correctly.

Common symptoms:

• Shuddering on take off
• Overheating
• Poor acceleration
• High revs with low power
• Metal debris in fluid
  
  

A worn torque converter, leaking seals, or failing solenoids can quickly contaminate the transmission. For signs and safety tips, see Warning.

Additional Codes Often Seen in the Same Vehicles

These issues appear frequently in Suzuki, Nissan, Mitsubishi, Toyota, Honda, and Subaru models:

CVT Belt Slip Detected

Causes RPM flare, loss of power and poor acceleration. Often, the first sign of internal wear.

Transmission Overheat Warning

Triggered when fluid breaks down or the cooling system cannot manage the heat load.

Solenoid Valve Fault

Affects pressure regulation and can cause jerking, harsh engagement or limp mode.

To understand why overheating and fluid breakdown cause so many problems, refer to What is a CVT.

Vehicles Most Likely to Show These Codes

These models frequently trigger transmission codes due to high mileage, CVT design and known pressure sensitivity:

• Suzuki Swift, SX4 
• Nissan Juke, March, Pulsar, Silphy and more
• Mitsubishi Mirage, ASX, Outlander, Colt and more
• Nissan Note and Tiida
• Honda Fit
• Toyota Corolla, RAV4, Alphard, Yaris and more
• Subaru Impreza
• Mitsubishi ASX
  
  

If you own one of the above vehicles and want to learn more about CVT care, visit our FAQ.

What to Do if You See an Error Code

Transmission codes should never be ignored. Some can be caused by minor issues such as fluid breakdown, but many relate to pressure loss or internal wear.

To learn more about our experience and why so many drivers choose us, visit our About Us page.
If you have warning lights, slipping, shuddering or code faults, contact our team through our Contact page, and we can guide you through the next steps.