Mercedes gearbox fault? Repair the original TCM.
Remanx tests and repairs Mercedes VGS, TCM and conductor plate faults for common 7G-Tronic, 7G-DCT, CVT and 9G-Tronic gearbox problems. Match your gearbox type and fault codes below, order the repair online, then send us your original electronic module.
Mercedes TCM / VGS common faults guide
Mercedes automatic gearbox faults are often blamed on the complete gearbox, valve body or mechatronic assembly. In many cases, the issue can be linked to the transmission control electronics instead — commonly called the TCM, TCU, VGS module or conductor plate depending on the gearbox type.
This guide helps you match the common Mercedes gearbox type, vehicle fitment and diagnostic fault codes to the correct Remanx repair service. If your gearbox type and fault codes match the guide, it is very likely you are dealing with the correct TCM/VGS repair route without needing to know every module part number first.
What do VGS, TCM, TCU and conductor plate mean?
VGS
VGS is Mercedes terminology commonly used for the transmission control electronics built into the gearbox mechatronic or conductor plate assembly. It is often understood as the fully integrated gearbox control module.
On these units, the VGS monitors internal gearbox signals such as speed, temperature, pressure and gear engagement, then controls the electronic and hydraulic operation of the transmission.
TCM / TCU
TCM means Transmission Control Module. TCU means Transmission Control Unit. In practical workshop terms, both refer to the electronic control unit responsible for gearbox operation.
A TCM/TCU uses sensor information from inside the gearbox and from the vehicle to decide how and when the gearbox should shift.
Conductor plate
On 722.9 7G-Tronic gearboxes, the conductor plate is the internal electronic plate/module assembly fitted within the gearbox mechatronic. It contains the control electronics and internal sensor circuits.
When the speed sensor circuits fail, the vehicle can log faults such as Y3/8N1, Y3/8N2, Y3/8N3, P0717, P0722, 2767 or 2768.
Mechatronic unit
The mechatronic is the combined electronic and hydraulic control assembly inside the gearbox. The Remanx repair service is for the electronic TCM/VGS module only.
We do not refurbish the valve body or solenoid valve block as part of this repair service. The electronic module should be separated before shipping to prevent damage from the heavier valve block.
Why a VGS fault can feel like a complete gearbox failure
A Mercedes automatic gearbox relies on accurate electronic feedback. The control module needs to know shaft speeds, gearbox oil temperature, pressure behaviour, selected gear and whether the expected gear ratio has been achieved. If that information is missing or incorrect, the gearbox may protect itself by limiting operation.
Speed sensor faults
If the VGS cannot read input, turbine or output speed correctly, it may not be able to confirm gear ratio or shift timing. This can cause limp mode, stuck-in-gear behaviour or RPM/speed sensor fault codes.
Temperature faults
Gearbox oil temperature is important for shift pressure, clutch control and gearbox protection. Incorrect temperature readings can cause warnings, poor shift quality or restricted operation.
Pressure faults
Modern Mercedes gearboxes rely on hydraulic pressure to apply clutches and engage gears. If the VGS sees an invalid pressure signal, the gearbox may prevent certain gears from engaging or enter limp mode.
Mercedes TCM / VGS modules we repair
Match your gearbox type, vehicle/chassis and fault codes below. If the gearbox and fault codes match, select the matching repair service and send your original electronic module to Remanx.
Mercedes VGS-FDCT / DKG / 7G-DCT TCM repair
7G-DCT dual clutch transmission
- Common vehicles: A-Class W176, B-Class W246, CLA C117, GLA X156.
- Common faults: oil temperature faults, internal temperature faults, RPM/speed sensor faults, pressure sensor faults, gearbox warnings and poor shift behaviour.
- Typical fault codes: 071400, 071100, 071000, 066700, 079100, 084000, 084500.
How the 7G-DCT gearbox works
The 724.0 / 724.1 7G-DCT is a 7-speed dual clutch transmission used in many Mercedes compact models. It uses two clutch circuits: one clutch controls one group of gears while the other prepares the next gear. The VGS-FDCT controls and monitors clutch operation, speed signals, temperature and pressure feedback.
Mercedes 7G-Tronic VGS / NAG2 / 722.9 conductor plate repair
7-speed automatic transmission
- Common vehicles: C-Class W203/W204, E-Class W211/W212, S-Class W221, ML W164, GL X164, CLK C209, CLS C219/C218, SLK R171/R172 and R-Class W251.
- Common faults: RPM/speed sensor faults, limp mode, harsh gear changes, stuck in gear and delayed engagement.
- Typical fault codes: Y3/8N1, Y3/8N2, Y3/8N3, P0717, P0718, P0722, P2206, P2207, 2767, 2768.
How the 722.9 7G-Tronic gearbox works
The 722.9 7G-Tronic is a 7-speed torque converter automatic gearbox. The VGS/conductor plate sits inside the gearbox mechatronic and monitors internal speed signals so the gearbox can calculate gear ratio and shift timing. Failed speed sensor circuits are a very common cause of limp mode and speed sensor fault codes on these units.
Mercedes CVT / Autotronic / Temic VGS2-FCVT repair
722.8 CVT automatic transmission
- Common vehicles: A-Class W169 and B-Class W245, including B200 CVT models.
- Common faults: RPM/speed sensor faults, no drive, limp mode and gear ratio faults.
- Typical fault codes: Y3/9B4, Y3/9B5, P0722, P0793, P0717, P0730, P1634.
How the 722.8 CVT gearbox works
The 722.8 Autotronic CVT does not use normal fixed gear steps. It changes ratio continuously using a variable pulley and belt/chain system. The Temic VGS2-FCVT module monitors speed signals and ratio control. If those readings fail, the gearbox can log speed sensor or gear ratio faults and may enter limp mode or lose drive.
Mercedes 9G-Tronic / VGS-NAG3 / 725.0 TCM repair
9-speed automatic transmission
- Common vehicles: C-Class W205/W206, E-Class W213/W214, S-Class W222/W223, GLC, GLE and GLS.
- Common faults: reverse gear cannot be engaged, pressure sensor signal invalid, limp mode and stuck in gear.
- Key fault codes: P073E00 Reverse Gear Cannot Be Engaged, P07B700 Pressure Sensor Signal Invalid.
How the 725.0 9G-Tronic gearbox works
The 725.0 9G-Tronic is a 9-speed torque converter automatic gearbox. The VGS-NAG3 manages shift strategy, hydraulic control and internal sensor feedback. Because this gearbox relies heavily on pressure and gear engagement feedback, internal VGS faults can cause very specific no-reverse or pressure sensor faults.
Quick fitment and fault code guide
Use this table to match the gearbox type, common vehicle fitment and fault codes. If the gearbox and fault codes match, it is very likely you have the matching TCM/VGS fault. If your fault codes are not listed, contact us first or send the module for investigation.
| TCM / gearbox type | Common vehicles / chassis codes | Typical fault codes / references | Product link |
|---|---|---|---|
|
VGS-FDCT / DKG 724.0 / 724.1 7G-DCT |
A-Class W176, B-Class W246, CLA C117, GLA X156 | 071400, 071100, 071000, 066700, 079100, 084000, 084500 | Order 7G-DCT repair |
|
7G-Tronic VGS / NAG2 722.9 conductor plate / TCM |
C-Class W203/W204, E-Class W211/W212, S-Class W221, ML W164, GL X164, CLK C209, CLS C219/C218, SLK R171/R172, R-Class W251 | Y3/8N1, Y3/8N2, Y3/8N3, P0717, P0718, P0722, P2206, P2207, 2767, 2768 | Order 7G-Tronic repair |
|
CVT / Autotronic 722.8 Temic VGS2-FCVT |
A-Class W169, B-Class W245, including B200 CVT | Y3/9B4, Y3/9B5, P0722, P0793, P0717, P0730, P1634 | Order CVT repair |
|
9G-Tronic / VGS-NAG3 725.0 9-speed automatic |
C-Class W205/W206, E-Class W213/W214, S-Class W222/W223, GLC, GLE, GLS | P073E00 reverse gear cannot be engaged, P07B700 pressure sensor signal invalid | Order 9G-Tronic repair |
Why repair the original Mercedes TCM?
Avoid coding after repair
When we repair your original TCM/VGS module, it remains the original unit from the vehicle. That means no coding is required after repair.
Avoid replacement cost
Repairing the original electronic module can avoid the cost and complications of replacing the full mechatronic, valve body or gearbox assembly.
Replacement options where possible
Where replacement options are available, units are typically pre-coded, cloned or data-transferred from the original module where possible.
Tested in-house
Remanx tests and repairs automotive electronics in-house, then returns the unit after repair and test where possible.
Fast turnaround
Turnaround is typically 1–2 working days from receipt where possible, depending on diagnosis, fault type, parts and workload.
Lifetime warranty
Completed repairs come with a lifetime warranty, giving garages and customers confidence when refitting the original unit.
How it works: Find. Send. Fixed.
Find
Match your gearbox type, vehicle/chassis and fault codes using the guide above. If the fault codes are not listed, contact us first or send the module for investigation.
Send
Order the repair online, remove the original electronic TCM/VGS module and send it to Remanx with your order details enclosed.
Fixed
Remanx tests the module, repairs it where possible, then returns it for refit. Original-unit repairs require no coding after repair.
Shipping and collection note
Mercedes TCM / VGS repair FAQs
Can my Mercedes TCM/VGS be repaired?
Many common Mercedes TCM/VGS faults can be repaired, especially the fault patterns listed in this guide. Repairability depends on the fault type and condition of the electronic module. If your fault codes are not listed, the repair service may not cover that fault, so contact us first or send the module for investigation.
Do I need to send the whole gearbox or mechatronic unit?
No. The repair service is for the electronic TCM/VGS module only. Please remove the valve body, solenoids and any heavy hydraulic/mechanical parts before shipping. We do not refurbish valve bodies as part of this service, and sending the heavy valve block attached can increase the risk of damage in transit.
Will it need coding after repair?
No coding is required after repair because we are repairing your original unit. Where replacement options are available, they are typically pre-coded, cloned or data-transferred from the original module where possible.
How long does the repair take?
Turnaround is typically 1–2 working days from receipt where possible. This can vary depending on diagnosis, parts availability, workload and the condition of the module.
What if my unit cannot be repaired?
If the unit cannot be repaired, we will advise you of the outcome. No-fix, no-fee applies where applicable, although return postage or testing terms may still apply depending on the order and service type.
How do I know which Mercedes TCM I have?
The best starting point is to identify the gearbox type, then use the fitment table and fault codes above. If the gearbox type, vehicle application and fault codes match, it is likely you have the matching TCM/VGS fault. If you are unsure, the next best check is the part number from the module. Some part searches may help, but fitment can vary by year, model and engine range.
What information should I send before ordering?
You do not need to send information before ordering if your gearbox type, vehicle fitment and fault codes match the guide. If your fault codes are not listed, the repair service may not cover that fault. In that case, contact us first with the gearbox type, fault codes and symptoms, or send the module for investigation.
Does the repair come with a warranty?
Completed Remanx repairs come with a lifetime warranty. The vehicle should still be checked for wiring, gearbox oil contamination, voltage supply, mechanical gearbox faults or valve body issues that could cause repeat symptoms.
Mercedes TCM fault in the workshop?
Match the gearbox type and fault codes, order the correct Mercedes TCM repair online, then send your original electronic module to Remanx. If your fault code is not listed, contact us first or send the module for investigation.
Call: 01227 314773 | Email: sales@remanx.com