VGS-NAG3 control unit, Mercedes 725.0 (9G-Tronic) – repair, cloning, programming
The VGS-NAG3 is the integrated control unit of the Mercedes-Benz 725.0 automatic gearbox – the 9-speed 9G-Tronic. It is built by Bosch: the Mercedes numbers A0009014800, A0009014900 and A0009015000 correspond to the Bosch numbers 0260550058, 0260550099 and 0260550095, and the central processor is a Renesas SH72560 microcontroller. The module is bolted to the valve body and, together with the set of nine solenoid valves and the speed sensors, forms the complete mechatronics unit.
We repair these control units on the bench – without the car. We replace the failed pressure sensor, the speed sensors and the solenoid valves, rework tired solder joints on the board and, where a module is beyond repair, clone its data onto a working donor.
The VGS-NAG3 control unit on our bench
What the VGS-NAG3 is, and how it differs from the VGS4-NAG2
The abbreviation VGS comes from the German Vollintegrierte Getriebesteuerung, meaning fully integrated gearbox control, and the NAG3 part from Neue Automatikgetriebe-Generation 3. The naming is misleading, because the digit next to VGS marks the generation of the control unit, while the NAG2/NAG3 part marks the generation of the gearbox. That is where the mix-ups come from when ordering parts and choosing programming tools.
VGS-NAG3 or VGS4-NAG2 – telling them apart quickly
- VGS-NAG3 – gearbox 725.0 (9G-Tronic), built by Bosch, Renesas SH72560 microcontroller, MB numbers from the A000901xxxx family.
- VGS2-NAG2 / VGS3-NAG2 / VGS4-NAG2 – gearbox 722.9 (7G-Tronic), built by Siemens VDO and, after the brand was taken over, by Continental; Infineon TC1767 microcontroller.
If you are looking for a service for the seven-speed 722.9 gearbox, the right page is our separate one: VGS4-NAG2 module programming and adaptation for Mercedes FBS4. The last photo in the gallery above shows exactly that – a Continental-built VGS3-NAG2 module, which makes clear how physically different it is from the Bosch unit out of the 9G-Tronic.
The 725.0 gearbox debuted in 2013 in the Mercedes E 350 BlueTEC (W212) and over the following years replaced the 722.9 in most longitudinally driven models. The VGS-NAG3 module itself is immobiliser-protected – by the FBS3 or the FBS4 system, depending on the model year – and stores data tied to the vehicle's VIN. That is why a new control unit cannot simply be plugged in and driven away.
Mercedes-Benz models with the 725.0 gearbox
- W205 / S205 / C205 / A205 – C-Class, from 2016
- W213 / S213 / C238 / A238 – E-Class, from 2016
- W212 / S212 – E-Class, 2013–2016
- W222 / V222 / C217 / A217 – S-Class, from 2015
- X253 / C253 – GLC, from 2015; GLC Coupé from 2016
- W166 / C292 – GLE and GLE Coupé, from 2015
- W167 / C167 – GLE and GLE Coupé, from 2019
- X166 – GLS (the facelifted GL), from 2016
- X167 – GLS, from 2019
- C257 – CLS, from 2018
- W463 (2018) – the new-generation G-Class
- W447 – Vito / V-Class after the facelift, from 2019
- R172 – SLC, from 2016 (apart from the AMG 55)
- W206 / W223 – C-Class and S-Class, the 725.1 variant
The most common VGS-NAG3 control unit faults
The 725.0 is a mechanically sound design, and a large share of the failures that reach us have their origin in the mechatronics electronics – although before diagnosing the control unit we always check the oil level and condition and that the valve body is clear. Here is what actually fails:
- A failed pressure sensor inside the module – the most frequently named weak point of this mechatronics unit. A failed diaphragm gives fault P07B700, an unprompted shift from D to N after stopping, harsh engagement and limp mode. It is fixed by replacing the sensor alone.
- A failure in the park-lock section – damage to the position sensor or to the park-lock solenoid valve inside the module. The symptom: the car cannot be moved off from P, or cannot be parked, often alongside a missing reverse gear.
- Tired solder joints and cracked tracks on the board – the connections between the electronics and the solenoid valves work through constant thermal cycles. Hence the faults that only appear once the gearbox has warmed up, such as the loss of reverse gear on hot oil (P073E00).
- Oil in the pass-through connector and in the loom – oil leaks past the seal of the gearbox pass-through connector and travels by capillary action along the loom to the outside, into the plug and on into the vehicle side. The module itself works inside the gearbox, so the problem is not “oil that has got to it” but a wet, corroded connector and the loss of communication with the control unit. Without replacing the connector and the seals, the problem comes back.
- Failed speed sensors Y3/8n1, Y3/8n2 and Y3/8n3 – integrated into the module and available as individual spare parts. They show up as codes from the input and output speed sensor group, limp mode and being locked in one gear.
- Sticking solenoid valves and contaminated oil – the 725.0 valve body has nine solenoid valves. Old ATF clogs the passages and wears the spools, which gives codes P076077 and P2810, harsh gear changes and current overloads on the output stages in the control unit.
Mercedes 725.0 gearbox fault codes
Most 725.0 codes take the form of a P with four characters and a two-digit extension (e.g. P073E00); alongside them Xentry also shows ordinary generic OBD-II codes. That is worth keeping in mind, because the numeric two- and three-digit code system familiar from Mercedes cars belongs to the older 722.6 gearbox and does not apply here. Speed sensor codes on this gearbox are read straight from Xentry — we do not carry over the designations known from the 722.9, because that leads nowhere.
VGS-NAG3 / 725.0 fault codes
| Fault code | Description and cause |
|---|---|
P073E00 | Reverse gear cannot be engaged. The most frequently cited code on a failed VGS-NAG3 control unit – no reverse gear, often showing up only once the oil has warmed up, sometimes together with a failure to engage D. |
P07B700 | An implausible signal from the pressure sensor inside the VGS-NAG3 module. The second classic fault of this gearbox – it shows up as the car dropping out of D into N after stopping, harsh engagement and limp mode. |
P07E400 / P07EF00 | The park position cannot be engaged or released. It follows from damage to the park-lock section of the control unit – the car may refuse to move off from P, or refuse to park. |
P07B571 | An electrical fault in the park-lock solenoid valve, which is driven directly by the VGS-NAG3 module. |
P07B623 / P07B624 | The park-lock position sensor signal is out of range – too high and too low respectively. A damaged measuring circuit inside the control unit. |
P076077 | A fault in solenoid valve no. 3 on the 725.0 valve body, or in its output stage in the control unit. It results in harsh gear changes and limp mode. |
P2810 | A short to earth in the pressure control valve circuit – Xentry shows the number of the specific valve alongside it. The typical result is no drive forwards or backwards while P and N work correctly, plus limp mode. The cause can be either the valve itself or its output stage in the control unit. |
P084014 | A short circuit or an open circuit in the oil pressure sensor circuit – the two-digit extension shows which way the fault runs. It concerns the internal pressure measuring circuit of the 725.0 mechatronics unit. |
P17F000 / P17F800 | A gear cannot be taught in, and the adaptation procedure has failed. Typical after a module has been replaced without the correct adaptation procedure, with worn oil, or with a damaged measuring circuit in the control unit. |
P0700 | A flag code stored on the engine control unit side when the VGS-NAG3 module has reported a fault of its own or has stopped responding. On its own it does not point to a cause – the gearbox module's memory has to be read. |
The signs of a failed VGS-NAG3 control unit
- A gearbox fault message in the instrument cluster asking you to visit a workshop
- Limp mode – stuck in a single, middle gear with no way to change
- The gearbox drops from D into N on its own after stopping, and re-selecting D takes several attempts
- No reverse gear – intermittent or total, often only once the oil has warmed up
- Delayed, harsh or juddering engagement of D and R, plus shift shock when changing gear
- Gears skipping and erratic downshifts
- Being unable to move out of P, or to select it
- The engine will not start because the P/N position signal has been lost
- No communication with the module during diagnostics – the module is missing or does not respond
- The current gear is not shown on the instrument cluster display
What we do with a VGS-NAG3 module
1. Repairing the original control unit
This is the option we recommend most often. The original memory stays in the module, so after the repair it does not have to be programmed or paired with the car – clearing the fault codes and running the adaptation is enough. The work covers:
- Replacing the pressure sensor (the most common cause of P07B700)
- Replacing the speed sensors Y3/8n1, Y3/8n2 and Y3/8n3
- Replacing failed solenoid valves on the valve body
- Reworking tired solder joints and rebuilding cracked PCB tracks
- Replacing the pass-through connector and the seals if oil has reached the loom
2. Cloning onto a donor module
When the control unit board is damaged beyond recovery – after water ingress and corroded tracks, for example – but the module can still be read, we transfer its contents onto a working example. Cloning carries over the maps, the VIN, the immobiliser data and the coding, so the cloned module works in the car exactly like the original, with no online programming at an authorised service centre.
3. Programming and personalisation
If the original module cannot be read, what remains is preparing a new or used control unit for the specific vehicle. It has to be said that on vehicles running the FBS4 system the range of possible operations is narrower than on the older FBS3 – we always establish this before taking the job on, from the VIN and the module's part number.
A new control unit is not a plug-and-play part
The VGS-NAG3 module stores data tied to the VIN and to the personalisation. A new control unit needs online programming (SCN coding), in which the manufacturer's server downloads the software file for the specific vehicle, followed by the full adaptation procedure with an adaptation drive. Fitting a module “out of another car” without those steps ends in no communication or in limp mode.
Oil in the 725.0 gearbox – why it matters for the control unit
The 725.0 gearbox requires a low-viscosity oil to the MB-Approval 236.17 specification. Total capacity is around 10 litres (a little more in the AMG versions), and a partial change without emptying the torque converter takes around 8 litres – we match the exact figure to the individual variant. The gearbox has no dipstick – the level is set by the overflow method within an oil temperature window of around 85–90 °C, which calls for a dedicated set of filling and draining adapters.
This thread runs through the whole page for a reason: neglected oil clogs the valve body passages and wears the valve spools, and that translates directly into current overloads on the output stages in the control unit. In other words – a share of VGS-NAG3 electronics failures starts with a neglected oil service. We also carry out dynamic oil changes and gearbox adaptation after a repair.
Why us?
- Repairing the module instead of replacing it – we replace the pressure sensor, the speed sensors and the solenoid valves and rework the solder joints – the original memory stays in the module, so it does not have to be paired with the car
- Cloning on the bench – we transfer the maps, the VIN, the immobiliser data and the coding from the old module onto a donor, with no online programming at an authorised service centre
- We tell the NAG2 and the NAG3 apart – a different manufacturer, a different microcontroller and a different gearbox – we match the tool to the specific control unit generation, not simply “to a Mercedes”
- No vehicle needed – the module can be sent in by courier – saving on transporting the car and on the time it stands idle
- Diagnosing the cause, not the symptom – we also check the pass-through connector and the loom, because oil that has found its way to the control unit comes back down the same path after every electronics repair
- Bench tested before it goes back – we connect the module to a tester and verify communication and solenoid valve control before returning it to the customer
How the service works
- Contact and scope of work – we check the module's part number, the fault codes and whether you have the original control unit
- Sending the module in, or a visit – the module can be sent by courier, or you can bring the car in
- Diagnostics on the bench – a communication test and checks on the pressure sensor, the speed sensors and the solenoid valve output stages
- Repair or cloning – replacing the failed components and reworking the solder joints, or transferring the data onto a donor module
- Verification – a second bench test and a check that the written data is correct
- Return and adaptation – the module goes back with a note on which adaptation procedure is required once it is fitted
Pricing
| Service | Description | Turnaround time |
|---|---|---|
| VGS-NAG3 module diagnostics | Bench test, assessment of whether a repair or a read is possible | Free with a booked job |
| Control unit repair | Replacing the pressure sensor, the speed sensors and the solenoid valves, reworking the solder joints | Quoted individually |
| VGS-NAG3 cloning | Transferring the maps, the VIN and the immobiliser data onto a donor module | Quoted by phone |
| Programming and personalisation | Preparing the module for the specific vehicle | Quoted by phone |
* Quoted once the module has been diagnosed. The price depends on whether repairing the original control unit is enough, or whether cloning onto a donor module is needed.
How do you book the service?
Call us and give us the module's part number from the label (e.g. A0009015000), the VIN and the fault codes that have been read. On that basis we will establish whether repairing the original control unit is enough or whether cloning will be needed – and we will arrange for the module to be sent in, or for you to bring the car.
Frequently asked questions
What is the VGS-NAG3 control unit?
The VGS-NAG3 is the fully integrated control unit of the Mercedes-Benz 725.0 automatic gearbox – the 9-speed longitudinal 9G-Tronic with a torque converter, which debuted in 2013. The electronics are built by Bosch – the Mercedes numbers A0009014800, A0009014900 and A0009015000 correspond to the Bosch numbers 0260550058, 0260550099 and 0260550095, and the central unit is a Renesas SH72560 microcontroller. The module is not a free-standing computer plugged into the loom: it is bolted to the valve body and, together with it, a set of nine solenoid valves and the speed sensors, forms the complete mechatronics unit.
How does the VGS-NAG3 differ from the VGS4-NAG2?
The VGS-NAG3 and the VGS4-NAG2 are control units for two different gearboxes, from different manufacturers and on different microcontrollers. The VGS-NAG3 runs the 9-speed 725.0 (9G-Tronic) gearbox, is built by Bosch and uses a Renesas processor from the SH725xx family. The VGS2-NAG2 was built by Siemens VDO, the VGS3-NAG2 is found both as a Siemens VDO and as a Continental unit (Siemens VDO was taken over by Continental in 2007), and the VGS4-NAG2 is Continental only; all three run on an Infineon TC1767 microcontroller and serve the 7-speed 722.9 (7G-Tronic) gearbox. The names are misleading, because the digit next to VGS marks the control unit generation, while the NAG2/NAG3 part marks the gearbox generation. Programming and cloning these families calls for different tools and different procedures.
Which Mercedes models have the 725.0 gearbox with the VGS-NAG3 control unit?
The 725.0 gearbox with the VGS-NAG3 module went first into the W212 E-Class in 2013 (the E 350 BlueTEC), then into the GLC X253 and the GLE W166 (from 2015), the W222 S-Class (from 2015), the W205 C-Class and the GLS X166 (from 2016), the W213 E-Class (from 2016), the CLS C257 and the new-generation W463 G-Class (from 2018), the GLE W167 and the GLS X167 (from 2019), and the facelifted Vito and V-Class W447 (from 2019). The key point is that those years say when each model range received the 9G-Tronic – earlier examples of the same bodies still have the 7-speed 722.9. The newer W206 C-Class and W223 S-Class use the related 725.1 variant.
Can a VGS-NAG3 control unit be cloned without a trip to a main dealer?
Cloning a VGS-NAG3 control unit on the bench is entirely practical and carries the maps, the VIN, the immobiliser data and the coding over from the old module – once cloned, the donor module works like the original, with no need for online programming at an authorised service centre. The condition is that the old module can still be read. If the control unit being fitted is new, or was cloned without the adaptation data being transferred, the full adaptation procedure with an adaptation drive is required.
Does a failed VGS-NAG3 control unit have to be replaced with a new one, or can it be repaired?
Repairing the VGS-NAG3 module itself is possible in most cases and works out better than replacing it: the failed pressure sensor, the speed sensors and the solenoid valves are replaced, and tired solder joints and tracks on the board are reworked. The key advantage of that repair is that the original memory stays in the module – afterwards it does not have to be programmed or paired with the car; clearing the fault codes and running the adaptation is enough. Replacing the complete mechatronics unit is the last resort, for extensive board damage after water ingress or corrosion.
A Mercedes 9G-Tronic drops from D into N on its own after stopping – what fault is that?
An unprompted shift from D into N after stopping in a Mercedes with the 9G-Tronic is the classic symptom of a failed pressure sensor inside the VGS-NAG3 module, stored as fault P07B700. The damaged sensor diaphragm stops delivering a plausible signal and the control unit goes into a safe state. It usually comes with harsh gear engagement and limp mode, and re-selecting D takes several attempts. The fault is repaired by replacing the sensor alone, without replacing the whole mechatronics unit.
Why does a Mercedes 725.0 lose reverse gear only once it is warm?
A loss of reverse gear that only shows up on hot oil is the typical picture of fault P073E00 in the Mercedes 725.0 gearbox. The usual culprit is the internal pressure sensor in the VGS-NAG3 module – the damaged diaphragm only becomes implausible once the oil has warmed up, so the control unit stops confirming that reverse has engaged correctly. Less often the cause is tired solder joints and cracked tracks on the board, which open up as they heat. That is why a car can drive normally in the morning and refuse to engage R after an hour on the road – and why diagnostics carried out on a cold gearbox will not show this fault.
Can gearbox oil get into the VGS-NAG3 control unit?
The VGS-NAG3 module itself works inside the gearbox, submerged in oil – so the problem is not “oil that has got to it” but oil that gets out. On Mercedes gearboxes it can leak past the seal of the pass-through connector and travel by capillary action along the loom to the plug and on into the vehicle side. The result is a wet, corroded connector and the loss of communication with the gearbox control unit – the module can disappear from diagnostics or stop responding. The repair covers replacing the pass-through connector and the seals, and sometimes a section of the loom as well; simply clearing the fault codes without removing the source of the leak is pointless.
Which oil, and how much of it, does the Mercedes 725.0 take?
The Mercedes 725.0 gearbox requires a low-viscosity ATF to the MB-Approval 236.17 specification. Total capacity is around 10 litres (a little more in the AMG versions), and a partial change without emptying the torque converter takes around 8 litres – we match the exact figure to the individual variant. The gearbox has no dipstick – the level is set by the overflow method within an oil temperature window of around 85–90 °C, which calls for a dedicated set of filling and draining adapters. This gearbox is very sensitive to oil cleanliness: a neglected change leads to a clogged valve body and shift shock when changing gear.
Is the VGS-NAG3 control unit tied to the vehicle's VIN?
The VGS-NAG3 control unit is an immobiliser-protected component – by the FBS3 or the FBS4 system, depending on the model year – and stores data tied to the VIN and to the personalisation. That means a new module is not a plug-and-play part: it needs online programming through Xentry (SCN coding, in which the manufacturer's server downloads the software file for the specific VIN) and personalisation. The alternative is cloning the original module on the bench, which transfers that data without the manufacturer's server being involved.