Decoding EBS 5 Knorr MAN Fault Codes
- SPN 597 FMI 5
- SPN 597 FMI 6
- SPN 603 FMI 5
- SPN 603 FMI 6
- SPN 609 FMI 0
- SPN 627 FMI 3
- SPN 629 FMI 0
- SPN 639 FMI 4
- SPN 639 FMI 4
- SPN 639 FMI 10
- SPN 645 FMI 4
EBS (Electronic Braking System) is an electronic brake control system that:
- distributes braking force between axles
- interacts with ABS, ASR, and ESP
- monitors the foot brake
- ensures safety during emergency braking
The EBS 5 Knorr control unit receives data from pressure sensors, brake pedal switches, CAN bus, and other MAN vehicle systems.
How to Read EBS Fault Codes (SPN / FMI)
EBS diagnostic errors are displayed in the format:
SPN XXX FMI X
- SPN (Suspect Parameter Number) — indicates a specific unit or parameter
- FMI (Failure Mode Identifier) — type of fault (open circuit, short circuit, incorrect signal, etc.)
FMI Examples:
- FMI 3 — signal not recognized
- FMI 4 — open circuit
- FMI 5 — short to ground
- FMI 6 — short to power
- FMI 10 — CAN communication error
Main Causes of EBS 5 Knorr MAN Faults
In practice, most faults are caused by:
- damaged wiring or connectors
- wear or malfunction of the foot brake module
- power supply issues (terminal 30, ground)
- J1939 CAN bus errors
- control unit software errors
- failure of the control unit itself
Timely decoding of the code helps prevent serious brake system failures and costly repairs.
What STOP and ABS Indications Mean
When EBS errors occur, different indication scenarios are possible:
- STOP yellow — fault exists but braking functions are preserved
- STOP red — critical fault, EBS functions limited or disabled
- ABS / ASR / ESP — auxiliary stability systems disabled
With a red indication, operation of the vehicle is not recommended until the cause is fixed.
How to Properly Diagnose EBS 5 Knorr
Recommended steps:
Read the fault code with a MAN diagnostic scanner / Find the SPN/FMI code below / Check:
- wiring condition
- EBS unit connectors
- power supply and ground
- sensor resistance
If necessary:
- update the control unit software
- replace the sensor or module
- replace the EBS unit
Important: replacing the unit without diagnostics often does not solve the problem if the cause is in wiring or power supply.
Why Using Code Decoding is Important
Using accurate EBS fault decoding allows you to:
- reduce repair time
- avoid unnecessary part replacements
- accurately identify the faulty unit
- increase MAN operational safety
- reduce vehicle downtime
EBS 5 Knorr MAN Fault Codes
Below is a complete list of EBS 5 Knorr fault codes, including:
- SPN 597 — foot brake module
- SPN 603 — foot brake switch 2
- SPN 609 — central control unit
- SPN 627 — EBS power supply
- SPN 629 — A-controller EBS
- SPN 639 — J1939 CAN bus
- and other diagnostic codes
Each code contains:
- fault description
- possible causes
- inspection and repair recommendations
Foot brake module, switch 1.
Short to ground (FMI 5).
STOP indicator lights yellow. User functions are not limited.
Possible electrical or mechanical fault in the foot brake module, wiring or connector damage.
Check wiring and connectors between the EBS unit (A402) and the foot brake module sensor (B337) for breaks and shorts.
Disconnect the connector from EBS unit (A402) and check resistance between SIG1 (X1/5) and GND (X1/4).
R_SW1 open: < 4.8 kΩ or > 6.5 kΩ
R_SW1 closed: 5.4 – 6.2 kΩ
If values are outside the acceptable range, replace the foot brake module.
Foot brake module, switch 1.
Short to power Ubat (FMI6).
STOP indicator lights yellow. User functions are not limited.
Electrical or mechanical fault in the foot brake module, wiring or connectors malfunction.
Check wiring and connectors between EBS unit (A402) and foot brake module sensor (B337) for shorts and breaks. Disconnect the connector from EBS (A402) and check resistance between SIG1 (X1/5) and GND (X1/4). R_SW1 open: R_SIG1 less than 4.8 kΩ or more than 6.5 kΩ. R_SW1 closed: R_SIG1 5.4 - 6.2 kΩ. If values are outside the permissible range, replace the foot brake module.
Foot brake module, switch 2.
Short to ground (FMI5).
STOP indicator lights yellow. User functions are not limited.
Electrical or mechanical fault in the foot brake module, wiring or connectors malfunction.
Check foot brake module wiring. If wiring is normal, replace the foot brake module.
Foot brake module, switch 2.
Short to power Ubat (FMI6).
STOP indicator lights yellow. User functions are not limited.
Electrical or mechanical fault in the foot brake module, wiring or connectors malfunction.
Check foot brake module wiring. If wiring is normal, replace the foot brake module.
Central control unit, B-controller.
Undefined fault (FMI0).
STOP indicator lights red, brake system control lamp also red. All user functions are disabled.
Software loading interrupted, microcontroller of EBS unit (A402) damaged.
Update software in EBS unit (A402), clear fault recorder. If the fault code appears again, replace EBS unit (A402).
J1939 data channel, CAN transmission.
No signal (FMI4).
STOP indicator lights red, brake system control lamp also red. All user functions are disabled.
EBS unit (A402) malfunction.
Clear fault recorder. If the fault code appears again, replace EBS unit (A402).
J1939 data channel, CAN transmission.
Open circuit (FMI10).
STOP indicator lights yellow. Disabled: retarder, ESP control, torque control (DTC), ASR engine control, ASR brake control.
CAN data channel wiring damaged, power circuit fault, or electromagnetic interference.
Check CAN data channel wiring and transmission unit wiring for breaks and shorts. Check correct operation of control units related to CAN transmission.
Tachograph connection channel, timeout exceeded.
No signal (FMI4).
STOP indicator lights yellow. User functions are not limited.
Electromagnetic interference, external device disconnected from data channel, external device not sending all messages due to fault.
Check data channel wiring for breaks and shorts. Check correct operation of external device.