Having problems with automatic gearbox faults, harsh gear changes, limp mode or a transmission warning light?
Freestorm tests and repairs transmission controllers, also known as TCU, TCM, transmission ECU or gearbox ECU units, for many vehicle makes and models.
If your car is sticking in gear, losing drive, showing PRNDS faults, failing to select reverse, changing gear badly or showing transmission fault codes, send us your vehicle details and we’ll help check the best repair option.
Testing and repair for common transmission control module and gearbox ECU faults
Send us your diagnostic codes, symptoms and part number before booking
A repair may save the cost of a new transmission controller
Typical turnaround from receipt of the unit
We help with part numbers, booking, delivery and updates
A transmission controller is the electronic unit that helps control an automatic, semi-automatic, CVT or automated manual gearbox. It may also be called a TCU, TCM, transmission ECU or gearbox ECU.
The transmission controller uses information from the engine, gearbox, wheel speed sensors, gear selector and other vehicle systems. It then decides when and how the gearbox should change gear.
Depending on the vehicle, the controller may manage gear shifts, gearbox pressure, clutch operation, solenoids, speed sensors, temperature sensors and communication with the engine ECU.
When the transmission controller fails, the car may change gear badly, get stuck in gear, go into limp mode, lose drive, fail to select reverse or show gearbox warning messages.
A faulty transmission controller can affect how the gearbox selects gears and how the car drives. The vehicle may still move, but the gear changes can become harsh, delayed or unpredictable.
In some cases, the car may go into limp mode, stay in one gear, refuse to select Drive or Reverse, or fail to start if the gearbox position cannot be confirmed.
Transmission faults can be confusing because the same symptoms can also come from other problems, such as low gearbox oil, worn clutches, valve body faults, solenoid faults, wiring issues, gear selector faults, speed sensor faults or internal mechanical gearbox damage.
That is why it is better to test the unit instead of replacing parts by guesswork.
Remanufacturing is a structured industrial process that returns used parts (cores) to reliable working condition through inspection, replacement of worn parts, rebuilding and testing.
Best when:
The original transmission controller, TCU, TCM or gearbox ECU can be tested and repaired.
Benefits:
Best when:
The original unit is badly damaged, burned, heavily corroded, physically broken, oil-damaged or not suitable for repair.
Benefits:
In many cases, testing the original unit is the best first step. If the transmission controller is too damaged to repair, we’ll let you know.
Transmission controller faults can show up in different ways. The fault may be constant or it may come and go.
The car may bang into gear, change gear aggressively or feel rough when shifting
The dashboard may show a gearbox, transmission or “visit workshop” warning
The gear display may flash, disappear or show incorrect gear information
The gearbox may hold one gear and refuse to shift normally
The car may suddenly lose gear engagement or feel like it has gone into neutral
The car may not engage Drive when selected
Reverse may not engage, or the car may delay before selecting reverse
The gearbox may limit operation to protect the transmission
The car may feel weak because the gearbox is not operating correctly
Some vehicles may not start if the transmission controller cannot confirm the correct gear or neutral position
Diagnostic equipment may not communicate with the transmission controller
Transmission faults may clear for a short time but come back after driving
Fault codes depend on the vehicle, gearbox type and diagnostic tool. These are common examples only. They should not be used as a final diagnosis without testing.
This is a general transmission fault code. It usually means the transmission system has stored more specific fault codes that need to be read
May point to an internal ECU or controller fault
Can indicate an internal transmission control module problem
The vehicle may not be detecting the selected gear range correctly
Can relate to gearbox speed sensor signals or internal transmission controller faults, depending on the vehicle
May point to output speed sensor signal faults, wiring or controller-related issues
The gearbox is not seeing the expected ratio between input and output speed
Can relate to pressure control solenoid circuits, wiring or internal controller output faults
May indicate a solenoid, wiring, valve body or controller output problem
May relate to pressure control, gearbox oil, internal gearbox condition or controller command issues
The vehicle cannot communicate correctly with the TCU / TCM
Some diagnostic tools may show faults such as control unit defective, internal speed sensor fault, conductor plate fault, transmission ECU fault or selector range implausible
Before sending the unit, please collect as much information as you can. This helps us check the fault faster and avoid delays.
This depends on the vehicle and the type of transmission controller.
In many cases, repairing the original TCU / TCM can help keep the original coding, configuration and vehicle data. This can make refitting simpler than using a new or used replacement unit.
Some vehicles may still need coding, adaptation, basic settings, clutch learn or gearbox relearn after the unit is refitted.
Freestorm handles the transmission controller testing and repair process from start to finish. We check the details, review the fault information, confirm the next steps and keep you updated.
Typical repair time: 5-10 working days from receipt of unit.
Typical turnaround is approximately 5-10 working days from receipt of the unit.
This can depend on the fault, testing time, repair work required, parts availability and courier times. We’ll update you if extra time is needed.
Fill in the booking form with your vehicle, part number and fault details
We confirm what to send and provide delivery instructions. Pack the unit securely and include your booking details
Your transmission controller is tested and repaired where suitable. If repair is not suitable, we’ll advise you
Your unit is returned with repair notes and warranty information where applicable
Freestorm can help with ABS faults across many common vehicle makes and models.
Audi
BMW
Ford
Mercedes-Benz
Volkswagen
Peugeot
Chery
Toyota
Volvo
Typical turnaround is approximately 5–10 working days from receipt of the unit, depending on the fault and repair requirements.
No, usually not. In most cases, the transmission controller, TCU, TCM, gearbox ECU or conductor plate is removed and sent separately. Send us a photo of the part and we’ll confirm what is required.
We can often advise from the fault codes, symptoms and part number, but final confirmation may require testing.
Warranty depends on the part type and repair carried out. We will confirm the applicable warranty before or after assessment.
Please send the vehicle make, model, year, gearbox type if known, registration/VIN if available, part number, fault codes and symptoms.
Yes. If the gearbox control system detects a serious fault, the car may go into limp mode or safe mode.
Yes, on some vehicles. If the car cannot confirm the correct gear position or gearbox status, it may prevent the engine from starting.
No. Harsh gear changes can also be caused by gearbox oil level or condition, valve body faults, solenoids, clutch wear, speed sensors, wiring or mechanical gearbox problems.
This depends on the vehicle. Repairing the original unit may help keep the original coding, but some vehicles may still need coding, adaptation, basic settings or gearbox relearn after refitting.
They are different names often used for the transmission control unit. Depending on the manufacturer, it may be called a TCU, TCM, transmission ECU, gearbox ECU or transmission control module.
Yes, PRNDS flashing can be linked to transmission controller, mechatronic, selector, wiring or gearbox faults. Diagnostics are needed to confirm the cause.
Send us your vehicle details, part number, fault codes or symptoms and we’ll help check whether transmission controller testing and repair is the right option.
