⚠️ Mercedes EPS2 Fault Codes – Important Notes & Troubleshooting

Mercedes EPS2 fault codes are displayed on the instrument cluster when the EPS2 (GS II) Gear Control Module detects errors during gearbox operation or during the gear learning process on Mercedes-Benz trucks such as Actros, Atego, and Axor.

These fault codes are critical diagnostic indicators and typically appear when there are issues related to clutch operation, gear selection, splitter or range learning, air supply, CAN communication, or signal mismatches between control units such as the FR, MR/PLD, GS, and Rear (Heck) Module.

This guide provides a clear list of common Mercedes EPS2 fault codes, their meanings, and likely causes to assist workshops, technicians, and fleet operators when troubleshooting GS II gearbox learning failures.

This Mercedes EPS2 fault codes reference is intended as a diagnostic support guide and should be used together with proper vehicle testing and professional diagnostic equipment.

📌 Mercedes EPS2 Fault Code List & Causes (GS II)

1️⃣ Neutral & Clutch-Related Fault Codes

🔴 GSII 05 – No safeguarding of neutral position

Possible causes:

  • No pneumatic air supply

  • Mechanical defect in transmission

  • Mechanical defect in transverse shift gate

  • Clamping sleeve or roll-pin issue

⚠️ The GS may not be correctly locked into the gearbox mechanism. Remove the GS and confirm correct mechanical engagement before reinstallation.

🔴 GSII 06 – Error in clutch value

Possible causes:

  • EEPROM hardware information invalid

  • Open circuit in clutch output stages

  • Clutch value not detected on CAN bus

🔴 GSII 09 – Learning error: Neutral position

Possible causes:

  • Gear position sensor mechanical or electrical fault

  • Air cushion fault in gear cylinder

  • Gear cylinder stiff or contaminated with oil

  • Internal mechanical transmission defect

2️⃣ Gear, Splitter & Gate Learning Fault Codes

🔴 GSII 10 – Learning error: Learned values for splitter are faulty

Possible causes:

  • Faulty solenoid valve connections (MS1, MS2)

  • Splitter sensor mechanical or electrical fault

  • Splitter cylinder mechanical defect

⚠️ Silicone applied to GS O-rings can enter internal ports and cause blockages, leading directly to this fault.

🔴 GSII 11 / GSII 12 – Learning error: Learned values for gear are faulty

Possible causes:

  • Faulty solenoid valve connections (MUB, MGB, MUE, MGE)

  • Gear sensor mechanical or electrical fault

  • Mechanical defect in gear cylinder

  • Transverse shift gate issue

🔴 GSII 13 / GSII 16 – Learning error: Learned values for gate are faulty

Possible causes:

  • Faulty solenoid valve connections (MG1, MG2)

  • Gate cylinder mechanical defect

  • Transmission mechanical fault

  • Transverse shift gate problem

🔴 GSII 17 – Learning error: Learned values for range are faulty

Possible causes:

  • Faulty solenoid valve connections (MR1, MR2)

  • Range sensor mechanical or electrical fault

  • Range cylinder mechanical defect

3️⃣ Sensor, Voltage & System-Related Fault Codes

🔴 GSII 18 – Fault at a solenoid valve or position sensor

Possible causes:

  • Check GS control unit fault memory for stored errors

🔴 GSII 19 – Learning error: Vehicle rolling

Possible causes:

  • Parking brake not engaged or not recognised by the vehicle

⚠️ The “P” symbol must be visible on the dashboard. If not, check the Rear (Heck) Module and brake status signal.

🔴 GSII 20 – Teach-in error: Undervoltage or overvoltage

Possible causes:

  • Faulty GS control unit

  • Faulty drive switch

  • Generator or voltage regulator fault

  • Battery discharged or defective

🔴 GSII 21 – Learning error: Clutch operation

Possible causes:

  • Clutch pedal released too early or too late

  • Operator error during learning process

🔴 GSII 22 – Learning error: Neutral selection interrupted

Possible causes:

  • CAN communication fault with FR module

  • Neutral button released during learning process

4️⃣ Transmission & Engine-Related EPS2 Fault Codes

🔴 GSII 23 – Learning error: Transmission type is invalid

Possible causes:

  • Gearbox parameters not learned correctly

  • Incorrect transmission data during minor learning

  • Wiring or connector faults

⚠️ This fault does NOT mean the incorrect GS unit is fitted.
It usually appears when Mercedes EPS2 fault codes are triggered after gearbox parameter changes, software updates, or MR/PLD horsepower modifications. A full minor and major learn must be performed.

🔴 GSII 24 – Learning error: Parking brake not operated

Possible causes:

  • Parking brake not engaged

  • Rear (Heck) Module not transmitting park-brake status to the instrument cluster

🔴 GSII 26 – Learning error: Engine running

Possible causes:

  • Engine must be OFF during minor learning

  • Engine should only be started when prompted during major learning

🔴 GSII 27 – Learning error: No engine torque or torque invalid

Possible causes:

  • FR or MR control unit fault

  • Engine torque data not available on CAN

🔴 GSII 28 – Learning error: Engine not started

Possible causes:

  • Engine not started within 10 seconds during major learning

🔴 GSII 29 – Learning error: No engine speed

Possible causes:

  • Engine speed signal missing

  • Continue diagnosis in FR and MR control units

🔴 GSII 30 – Learning error: Idle throttle

Possible causes:

  • Accelerator pedal pressed during learning

  • FR system fault

🔴 GSII 31 – Learning error: Clutch clearance

Possible causes:

  • Incorrect clutch operation during learning

  • Clutch travel sensor fault

  • Clutch servo assistance mechanical defect

  • Faulty central speaker (not applicable to EPS2 EAS vehicles)

🔴 GSII 32 – Learning error: Countershaft speed

Possible causes:

  • Countershaft RPM sensor fault

  • Internal transmission mechanical defect

⚠️ Mercedes EPS2 Fault Codes – Important Notes & Troubleshooting

  • Always engage the parking brake and confirm the “P” symbol is visible on the dashboard

  • Ensure full operating air pressure before starting any learning process

  • Use supplied O-rings when refitting GS units — never silicone

  • Fully depress and release the clutch smoothly during learning

  • If learning fails, inspect wiring, sensors, air supply, CAN communication, and harness connections before reattempting

Understanding Mercedes EPS2 fault codes correctly helps prevent repeat learning failures, unnecessary component replacement, and long-term EPS2 system damage.

Mercedes EPS2 fault codes displayed on the instrument cluster do not confirm that the EPS2 (GS II) unit is defective. These codes are general indicators and may relate to multiple systems interacting with the gearbox, including pneumatic supply, sensors, wiring, CAN communication, and associated control modules.

Due to the limited diagnostic detail provided by dashboard fault messages, accurate diagnosis often requires a qualified auto-electrician and the use of Mercedes-Benz STAR Diagnostics. STAR Diagnostics allows full interrogation of the EPS2, FR, MR/PLD, and related systems and is strongly recommended whenever transmission or gearbox-related faults are present.

🔧 EPS2-Related Repairs & Connectors

 

⚠️ Disclaimer

Autolectronix takes no responsibility for the accuracy of the above information. If you have any hesitations regarding troubleshooting or repairs, consult a qualified auto-electrician or gearbox specialist.

This Mercedes EPS2 fault codes troubleshooting guide is intended for workshops, technicians, and fleet operators diagnosing GS II gearbox learning failures on Mercedes-Benz commercial vehicles.

Mercedes PLD MR Fault Codes Explained (MP1, MP2, MP3)

Mercedes PLD MR fault codes are logged when the PLD MR (Motor-Regulator) control unit detects a problem affecting engine operation, injector control, communication, or immobiliser functions. These fault codes are commonly seen on Mercedes-Benz Actros, Atego, and Axor trucks, as well as Fuso trucks, Bell equipment, and Marcopolo buses using PLD engine management systems.

Understanding Mercedes PLD MR fault codes allows technicians and fleet operators to quickly identify whether a problem is related to misfires, CAN communication, power supply, immobiliser issues, or internal ECU damage. This guide explains the most common PLD MR fault codes, what they mean, and how they are typically resolved.

What Is the Mercedes PLD MR Module?

The Mercedes PLD MR module is a critical engine control unit responsible for:

  • Injector and fuel delivery control

  • Engine timing and combustion management

  • CAN communication with FR, CPC, and other control units

  • Immobiliser and transponder authorisation

  • Monitoring voltage, sensor references, and actuator outputs

When faults occur, the PLD MR stores fault codes that help diagnose the root cause of engine and starting problems.

Mercedes PLD MR Fault Codes – Communication & Power Faults

These Mercedes PLD MR fault codes indicate communication failures or power-related issues.

MR 0300 – No Communication with Engine ECU

Cause:

  • CAN bus wiring fault

  • Corroded connectors

  • Internally failed PLD MR

Fix:

  • Inspect CAN wiring and connectors

  • Bench test PLD MR

  • Repair or replace the module if required

MR 0311 – Supply Voltage Too Low

Cause:

  • Low vehicle battery voltage

  • Internal power supply circuit failure

Fix:

  • Test vehicle power and ground feeds

  • Repair PLD MR if supply voltage is correct

MR 0350 – Module Not Powering Up

Cause:

  • Severe internal damage

  • Corrosion on PCB

Fix:

  • Major PLD MR repair (circuit rebuild usually required)

Mercedes PLD MR Fault Codes – Injector & Misfire Errors

Injector-related Mercedes PLD MR fault codes are the most commonly reported issues.

MR 0401 – Injector Bank 1 Fault

Cause:

  • Driver circuit failure on Bank 1

Fix:

MR 0402 – Injector Bank 2 Fault

Cause:

  • Driver circuit failure on Bank 2

Fix:

MR 0403 – Injector Fault on Both Banks

Cause:

  • Both injector driver circuits failed

Fix:

Mercedes PLD MR Fault Codes – Actuator & Starter Errors

MR 0501 – Starter Actuator Fault

Cause:

  • Failed driver circuits

  • Wiring fault between PLD MR and starter actuator

Fix:

  • Bench testing and component-level repair

MR 0520 – Injector Actuator Control Fault

Cause:

  • Incorrect or missing injector control signals

Fix:

  • Internal PLD MR component repair

Mercedes PLD MR Fault Codes – Immobiliser & Transponder Issues

MR 0600 – No Transponder Detected

Cause:

  • Key not recognised

  • Lost transponder data

  • Faulty transponder circuitry

Fix:

MR 0601 – Immobiliser Active

Cause:

  • Immobiliser blocking engine start

Fix:

  • Software modification on FR or CPC/FR

Mercedes PLD MR Fault Codes – Corrosion & Environmental Damage

MR 0700 – Internal Corrosion Detected

Cause:

  • Water ingress into PLD MR

Fix:

MR 0710 – Sensor Reference Voltage Fault

Cause:

  • Corroded PCB tracks

  • Shorted reference circuits

Fix:

  • PCB repair and internal cleaning

When to Repair vs Replace a Mercedes PLD MR

Important Diagnostic Note

Mercedes PLD MR fault codes do not automatically mean the PLD MR module is faulty. These fault codes are often symptoms, not confirmations. Wiring faults, sensor failures, CAN communication issues, power supply problems, or immobiliser errors can all trigger identical codes.

For accurate diagnosis, a qualified auto-electrician and Mercedes-Benz STAR Diagnostics are strongly recommended. STAR Diagnostics allows full interrogation of the PLD MR, FR, CPC, and related systems and provides far more detail than dashboard fault messages alone.

Mercedes PLD MR Repairs by Autolectronix

At Autolectronix, we specialise in:

We support Mercedes-Benz trucks, Fuso, Bell equipment, and Marcopolo buses, offering a cost-effective alternative to ECU replacement.

📧 Contact Autolectronix

Email: sales@autolectronix.co.za
Phone: +27 31 700 1420

⚠️ Disclaimer

This information is provided as a technical guide only. Autolectronix accepts no responsibility for incorrect diagnosis or installation. Always consult a qualified technician when dealing with engine management systems.

🚛 Mercedes EPS2 (GS II) Gear Control Learning Process – Step-by-Step Guide

Mercedes EPS2 Gear Learning Process procedures are required after repairs, replacements, or adjustments to the EPS2 (GS II) Gear Control Module used in Mercedes-Benz trucks such as Actros, Atego, and Axor.
This learning process may also be required after engine power (horsepower) changes performed via MR/PLD programming, as torque characteristics and shift parameters must be re-synchronised between the engine management system and the EPS2 gearbox controller.

🚛 Mercedes EPS2 Gear Learning Process – Minor Learning (GS II)

This Mercedes EPS2 Gear Learning Process (Minor Learning) is required when replacing clutch-related components or position sensors for clutch, splitter, range, gear, or gate.

Preparation (Before Starting Learn Process)

✅ Ensure the parking brake is engaged (must be visible on the dashboard).
✅ Battery voltage must be stable (>24V).
✅ Clear any existing faults in the control unit before starting.
✅ Ensure air pressure is at full operating pressure.
✅ Both the cab harness (White Plug) and the gearbox harness (Black Plug) must be fully connected and locked into place using the locking mechanism on the plug.
✅ Do not use silicone, cable ties, or any other method to hold the plug in place, as this will compromise proper operation.
✅ When we return an EPS2 unit after repair, we will provide you with two O-rings for the splitter seal from the EPS2 to the gearbox.
✅ Do not use silicone on these seals, as it may cause blockages within the EPS2 and lead to a "GSII 10 Learning Error."

Step-by-Step Process:

  1. Switch off the ignition.
  2. Engage the parking brake.
  3. Fully depress the clutch pedal and hold (skip this for EAS vehicles).
  4. Press and hold the "Neutral" button.
  5. Switch on the ignition.
  6. Wait for the "Neutral (N)" indicator to flash on the display.
  7. Release the clutch when you hear signal tone 1 (skip this for EAS vehicles).
  8. Fully depress the clutch when you hear signal tone 2 (skip this for EAS vehicles).

Completion:

  • If the "Neutral" indicator appears, the process is successful.
  • If flashing arrows appear, the learning process is still in progress.
  • If programming fails, check for fault codes and repeat the process.

🚛 Mercedes EPS2 Gear Learning Process – Major Learning (GS II)

This Mercedes EPS2 Gear Learning Process (Major Learning) is required when replacing the EPS2 control unit, installing a different transmission, or after retrofitting a Telma retarder.

Preparation (Before Starting Learn Process)

✅ Ensure the parking brake is engaged (must be visible on the dashboard).
✅ Battery voltage must be stable (>24V).
✅ Clear any existing faults in the control unit before starting.**
✅ Ensure air pressure is at full operating pressure.
✅ Both the cab harness (White Plug) and the gearbox harness (Black Plug) must be fully connected and locked into place using the locking mechanism on the plug.
✅ Do not use silicone, cable ties, or any other method to hold the plug in place, as this will compromise proper operation.
✅ When we return an EPS2 unit after repair, we will provide you with two O-rings for the splitter seal from the EPS2 to the gearbox.
✅ Do not use silicone on these seals, as it may cause blockages within the EPS2 and lead to a "GSII 10 Learning Error."

 

⚠️ Important Note – Parking Brake Status (P Symbol)

When performing the Mercedes EPS2 Gear Learning Process, the parking brake must be correctly recognised by the vehicle, not just mechanically applied.
The “P” symbol must be visible on the instrument cluster before starting the learning procedure.

If the P symbol is not displayed, the EPS2 learning process will not start or will fail, even if the parking brake is physically engaged. This condition usually indicates:

  • A fault in the Rear / Heck Module

  • A problem in the parking brake signal circuit

  • A vehicle-side CAN communication issue

  • Incorrect brake status input to the GS II / EPS2 system

If the P symbol does not appear, the fault must be diagnosed and resolved before attempting the learning process, otherwise repeated learning failures or fault codes will occur.

 

Step-by-Step Process:

  1. Switch off the ignition.
  2. Engage the parking brake.
  3. Fully depress the clutch pedal and hold (skip this for EAS vehicles).
  4. Press and hold the "Skip-Shift" button and "Neutral" button.
  5. Switch on the ignition.
  6. Release the clutch when you hear signal tone 1 (skip this for EAS vehicles).
  7. Fully depress the clutch when you hear signal tone 2 (skip this for EAS vehicles).
  8. Start the engine when the "Neutral (N)" indicator flashes.
  9. Release the clutch when you hear signal tone 3 (skip this for EAS vehicles).
  10. Fully depress the clutch when you hear signal tone 4 (skip this for EAS vehicles).
  11. Release the clutch when you hear signal tone 5 (skip this for EAS vehicles).
  12. Fully depress the clutch when you hear signal tone 6 (skip this for EAS vehicles).

Completion:

  • If the "Neutral" indicator appears, the process is successful.
  • If programming fails, check fault codes and repeat the process.
  • If an error occurs, the fault code will be displayed on the instrument cluster.

💡 Notes:

  • For vehicles with EAS, the clutch operates automatically, so clutch pedal actions can be ignored.
  • During learning, always depress the clutch fully and release smoothly to prevent damage.
  • If the process fails, inspect wiring, sensors, air supply, CAN communication, and harness connections before attempting again.

🔧 EPS2-Related Repairs & Connectors

 

⚠️ Disclaimer

Autolectronix takes no responsibility for the accuracy of the above information. If you have any hesitations regarding installation or the learning process, please consult a qualified auto-electrician.

This Mercedes EPS2 Gear Learning Process guide is intended for workshops, technicians, and fleet operators working on GS II transmissions. Following the correct Mercedes EPS2 Gear Learning Process helps prevent shift errors, fault codes, and unnecessary EPS2 failures after repairs.

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