Mercedes EPS2 Fault Codes – GS II Error List & Troubleshooting Guide

Mercedes EPS2 fault codes displayed on Actros instrument cluster during GS II gearbox learning process

⚠️ 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.

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