In paper machinery, winding equipment, printing lines, coating machines, textile machinery, metal processing lines, and continuous feeding systems, a high-power servo drive often does much more than simply rotate a motor. It may also participate in speed synchronization, tension control, line-speed measurement, measuring-roll feedback, position compensation, and machine interlocking.
Therefore, when a Bosch Rexroth IndraDrive C system is removed from a customer’s machine and brought to a repair workshop, it usually cannot be tested like an ordinary inverter. Supplying three-phase power, 24 V control power, and connecting the motor is often not enough to make the drive run. The real difficulty is not only determining whether the power module is damaged, but also understanding the original control architecture, encoder topology, external I/O supply, serial communication control, and parameter logic.
This is especially true for an IndraDrive C system equipped with a configurable control section, X15 parallel I/O interface, X2 serial communication, and an external measuring-roll encoder. During startup, the drive checks several conditions in sequence. After one fault is removed, the next deeper-level fault may appear. For example, when F2044 is cleared and F2042 appears afterward, this does not necessarily mean a new fault has been created. It often means the drive has passed the previous external I/O power check and has now started checking the encoder feedback chain.
This article uses a typical HCS03.1 high-power IndraDrive C system with a CSB01.1C control section, external measuring encoder, and PLC serial control architecture as an example. It explains how to diagnose the drive offline, identify the real function of each interface, understand F2044 and F2042, connect IndraWorks Ds through X2, avoid unsafe parameter changes, and establish a safe temporary bench-test method.
1. IndraDrive C Is Not an Ordinary VFD
A Bosch Rexroth IndraDrive C drive consists of a power section and a control section. The power section handles three-phase rectification, DC bus energy, inverter output, braking chopper operation, thermal management, and motor power output. The control section handles motion control, encoder evaluation, digital I/O, communication, diagnostics, parameter management, and interaction with PLC or CNC systems.
For example, the drive model:
HCS03.1E-W0150-A-05-NNBV
belongs to the high-power compact IndraDrive C series. It is typically used for large main drives, winding rollers, drawing rollers, tension-control systems, and other high-torque servo applications. This type of drive must not be treated like a small servo amplifier or a basic frequency inverter during bench testing.
A key point is that the same HCS03 power section can be fitted with different control sections. The control section determines which interfaces and functions are available: serial communication, Profibus, SERCOS, analog input, parallel I/O, encoder options, positioning mode, spindle mode, or speed synchronization.
Therefore, before testing the drive, the technician must identify three things:
Power section model
Control section model
Firmware and parameter set
Looking only at the power section model is not enough. The real control logic is determined by the control section, firmware, and application parameters.
2. Correctly Identifying X2, X4, X8, and X15
In this case, the control section model is:
CSB01.1C-PL-ENS-EN2-...
The important parts are:
CSB01.1C = configurable single-axis control section
PL = parallel interface option
ENS = standard encoder interface
EN2 = second encoder / optional encoder interface
This means the drive is not a simple fixed-I/O unit. It is a configurable drive that can be controlled through communication, mapped I/O, and encoder functions.
The important connectors are:
X2 = RS232 serial interface
X15 = parallel I/O interface
X4 = optional encoder / measuring encoder interface
X8 = motor encoder or standard feedback interface
In the customer’s electrical drawing, the system uses two encoders:
X8 → motor encoder
X4 → measuring-roll encoder
This means the motor encoder and measuring encoder are both part of the original system. The motor encoder is used for motor feedback, speed control, and commutation. The measuring-roll encoder is likely used for actual material speed, length measurement, synchronization, or tension-related control.
If only the motor and drive are brought to the workshop while the measuring-roll encoder remains on the machine, the drive may report an encoder-related fault because the original parameter set still expects Encoder 2 to exist.
3. F2044 and F2042 Must Be Understood as Sequential Diagnostics
When the drive is powered on without the required X15 external I/O supply, it may display:
F2044
External power supply X15 error
This means the X15 external I/O power supply is missing, incorrect, or not detected. For a control section with a parallel interface, X15 is not just an optional connector. It may be used for inputs, outputs, enable chains, interlocks, status signals, and machine logic.
After the X15 external 24 V supply is connected correctly, F2044 may disappear. Then the drive continues checking the next required conditions. If the next displayed fault is:
F2042
Encoder 2: encoder signals incorrect
this usually means the drive has now detected a problem with the second encoder channel. In this case, the second encoder corresponds to the external measuring-roll encoder that is missing from the bench setup.
This sequence is normal:
X15 not powered → F2044
X15 powered correctly → F2044 cleared
Missing Encoder 2 → F2042
Therefore, F2042 after F2044 does not automatically mean the drive or motor has been damaged. It means the diagnosis has moved to the next dependency.
4. Supplying X15 with 24 V Does Not Mean the Drive Can Run from I/O
Many technicians assume that once X15 has 24 V, the motor can be started by applying 24 V to a few digital inputs. This is not always true.
On a configurable IndraDrive control section, the physical X15 pins are only hardware inputs and outputs. Their actual function is defined by parameters. One input may be mapped as Drive ON in one project, but as a limit switch, mode selector, reset, external interlock, or PLC handshake signal in another project.
Possible functions include:
Drive ON
Drive Halt
Fault Reset
Jog +
Jog -
Forward
Reverse
External enable
Mode selection
Limit switch
PLC interlock
Status feedback
Therefore, knowing the physical pin number is not enough. The current parameter mapping must also be known.
In this case, the customer’s electrical drawing shows a PLC serial communication path:
PLC serial module
↓
RS485
↓
HAS05.1-005 RS232/RS485 converter
↓
Drive X2
This strongly suggests that the original machine does not use X15 as the main command source. Instead, the PLC probably sends the control word, speed command, enable sequence, reset, and operating mode through X2 communication.
So X15 power is required to clear F2044, but X15 may not have authority to start the motor unless the control source and I/O mapping are changed.
5. X2 Is the Key Diagnostic Interface
The X2 connector on this IndraDrive is an 8-pin Mini-DIN RS232 serial interface. It is used for:
Parameter reading
Parameter writing
Diagnostics
Fault history
DriveTop / IndraWorks communication
Serial master control
Connection to RS232/RS485 converter
The correct X2 pin assignment is:
1 = RTS
2 = CTS
3 = TxD
4 = GND
5 = RxD
6 = Vcc
7 = n.c.
8 = n.c.
For connection to a PC through RS232, the basic wiring is:
Drive X2-3 TxD → PC DB9-2 RxD
Drive X2-5 RxD → PC DB9-3 TxD
Drive X2-4 GND → PC DB9-5 GND
X2-6 is Vcc and should not be connected to the PC serial port. X2 is RS232, not TTL and not RS485. A USB-TTL adapter must not be connected directly to X2. If the computer has no real serial port, a proper USB-RS232 adapter should be used.
The original machine may use a HAS05.1-005 converter. This converter allows the PLC RS485 side to communicate with the drive’s RS232 X2 port. Therefore, the field system may look like RS485 from the PLC side, but the drive X2 itself remains RS232.
6. The Standard Four-Key Panel Cannot Replace IndraWorks Ds
The small four-key panel on the drive usually has:
Esc
Up
Down
Enter
It can be used for basic status display, fault display, simple command confirmation, and limited menu operations. However, it is not suitable for full parameter work.
It cannot reliably perform these tasks:
Export complete parameter set
View all P-0 parameters
View all S-0 parameters
Edit encoder configuration safely
Compare original and modified parameters
Change control source mapping safely
Check live X15 input status
Check serial communication status
Save and restore complete parameter files
For this case, the correct tool is:
IndraWorks Ds
or IndraWorks Engineering with drive commissioning functions
A comfort control panel may allow more parameter editing than the standard four-key panel, but for a repair workshop, software is much safer because it allows parameter backup, comparison, online diagnostics, and easier restoration.
Before changing anything, the technician should connect through X2, read the drive online, and save the original parameters.
7. Easy Startup Is a Temporary Test Method, Not a Permanent Machine Solution
IndraDrive provides an Easy Startup function for commissioning and temporary testing. When activated, it can temporarily bypass the original master communication and allow simplified local test operation.
The key point is that Easy Startup is not intended to permanently replace the original PLC or CNC logic. It is useful for bench testing because it can help verify:
Drive power section
Motor feedback
Motor rotation
Basic speed control
Low-speed operation
Fault response
However, Easy Startup cannot replace the original measuring-roll synchronization, tension control, PLC logic, line-speed control, or production process control.
For a repair bench, Easy Startup is useful only after the basic faults have been cleared:
X15 external power OK
Encoder faults resolved or temporarily configured
Motor feedback correct
Main power safe
Emergency stop available
Motor mechanically fixed
It should not be used as a permanent operating mode for the customer’s machine.
8. Encoder 2 Should Not Be Permanently Disabled Without Understanding the Machine Function
When F2042 appears, one possible temporary test method is to disable Encoder 2 in the parameter set. However, this must be treated as a temporary bench-test action only.
The external measuring encoder may be used for:
Actual material speed
Line speed measurement
Length counting
Tension control
Slip detection
Roll diameter compensation
Synchronization
Feed ratio calculation
If it is permanently disabled, the motor may run, but the machine process may become invalid or unsafe.
Possible consequences include:
Incorrect line speed
Incorrect length measurement
Unstable tension
Roll synchronization error
Material breakage
Slip not detected
Wrong feed ratio
Unexpected speed correction
A safer temporary method is to connect a compatible test encoder to X4. If the original measuring encoder used 8 wires:
+5V
0V
A / A-
B / B-
Z / Z-
then the temporary encoder must be a 5 V TTL differential or RS422 line-driver type. It must not be a 24 V encoder, NPN encoder, PNP encoder, or open-collector single-ended encoder.
Even if the electrical signals are compatible, the pulse count may be different from the original encoder. This may clear F2042 but still make the machine measurement wrong. That is acceptable only for bench testing, not for final machine operation.
9. A Correct Offline Diagnosis Sequence
For a complex IndraDrive C system, the correct sequence is more important than speed.
Step 1: Identify all hardware
Record:
Power section model
Control section model
Firmware version
Motor model
Motor encoder type
External encoder type
PLC model
Communication module
HAS05 converter model
Brake resistor
Original cable connections
Step 2: Preserve original information
Before removing or changing wires, take photos of:
X15 wiring
X2 communication cable
X4 encoder cable
X8 motor encoder cable
Motor power cable
Brake resistor cable
Main power cable
24 V wiring
Grounding
PLC terminal numbers
Step 3: Clear basic power-related faults
If F2044 is present, solve the X15 external 24 V power issue first. Do not attempt to start the drive while F2044 is active.
Step 4: Resolve encoder faults
If F2042 appears after F2044 is cleared, check whether Encoder 2 is missing, incorrectly wired, or expected by the parameter set.
Step 5: Confirm the real control source
Determine whether the drive is controlled by:
X2 serial communication
Profibus
SERCOS
Analog input
X15 parallel I/O
Easy Startup
Local software test mode
Do not assume X15 can start the drive unless the parameter mapping confirms it.
Step 6: Back up parameters before modification
Before disabling Encoder 2 or switching to local I/O control, save the full parameter set. Never perform Load Defaults or firmware updates without a backup.
Step 7: Perform only low-speed bench testing
The motor must be mechanically fixed. Use low speed, low torque, short test duration, and a real emergency stop. A high-power 30 kW motor with high torque must never be allowed to run freely on a bench.
10. Parameter Modification Principles
Any parameter change must follow four principles:
Backup first
Change as little as possible
Record original values
Restore after testing
Do not perform:
Load Defaults
Factory reset
MMC parameter loading
Firmware upgrade
Random I/O remapping
Permanent encoder disabling
Permanent control source change
Without a parameter backup, even a simple change can make the drive incompatible with the customer’s PLC program or mechanical system.
Important parameter groups include:
Encoder 1 configuration
Encoder 2 configuration
Optional encoder assignment
Control word source
Speed command source
Communication settings
I/O mapping
Operating mode selection
Drive Halt / Drive ON logic
The exact parameter names and values may vary by firmware version. Therefore, the correct procedure is to go online with IndraWorks Ds, read the current values, save the parameter file, and only then make temporary modifications.
11. “Motor Can Rotate” Does Not Mean “Machine Is Repaired”
For a high-power servo system, testing should be divided into levels.
Level 1: Drive powers up correctly
Confirm:
Display works
No fatal hardware fault
No F2044
Control section identified
Parameters readable
Software can connect
Level 2: Feedback and interlocks are valid
Confirm:
Motor encoder OK
External encoder OK or temporarily handled
Temperature feedback OK
Drive Halt status correct
Emergency stop available
Grounding correct
Main contactor logic safe
Level 3: Low-speed motor operation
Confirm:
Motor turns in the correct direction
No abnormal noise
Current is stable
Feedback is stable
No encoder jumping
No DC bus abnormality
Stop behavior normal
Level 4: Machine process operation
Confirm:
PLC communication normal
Measuring-roll feedback normal
Line-speed calculation correct
Tension stable
Synchronization correct
Original machine logic restored
Only Level 4 proves the customer’s machine is truly restored. A successful bench spin only proves that the drive and motor can run under simplified conditions.
Conclusion
The diagnosis of a Bosch Rexroth IndraDrive C high-power servo system cannot be reduced to simply applying power and forcing an enable input. A system with HCS03.1 power section, CSB01.1C control section, X15 parallel I/O, X2 serial communication, motor encoder, and external measuring encoder must be treated as a complete motion-control system.
F2044 indicates that the X15 external I/O power supply is missing or incorrect. Once it is corrected, F2042 may appear because the drive now checks Encoder 2. If the original machine uses a measuring-roll encoder on X4 and this encoder is not present during bench testing, F2042 is expected.
The proper repair method is:
Identify hardware
Preserve wiring information
Clear X15 power faults
Confirm encoder topology
Connect IndraWorks Ds through X2
Back up parameters
Temporarily configure a safe bench-test mode
Run only low-speed tests
Restore all original parameters
Verify the complete machine at the customer site
Only by understanding the relationship between power section, control section, PLC communication, X15 I/O, X2 serial interface, X4/X8 encoder structure, and the original parameter set can a technician diagnose and repair this type of IndraDrive C system safely and reliably.
