­­­Technical Bulletin
Bulletin No: TCH-11-003 Rev 000
Subject:

Initial Release Date: August 1, 2023 Revision Date: N/A

Page: 1 of 8

Bendix® 600-volt Electric Screw Module 1 (ESM1)

OVERVIEW
The Bendix® ESM1 is an electric air compressor that generates and supplies compressed air for a commercial vehicle air
brake system. The major components that constitute the ESM1 assembly are the high-voltage electric motor (E-motor) (with
an integrated inverter and CAN interface) and the oil-injected rotary screw compressor. Using electrical energy from the
batteries of the Electric Vehicle (EV), the electric motor drives the compressor using a flange coupling connection between
the two (2) sub-components to produce compressed air. See Figure 1.
The ESM1 is a high-voltage, liquid-cooled device, and requires coolant from the vehicle’s cooling circuit during operation.
The coolant runs in series – first through the motor and then through the heat exchanger on the compressor. The compressor
has a self-contained oil system and does not require oil fed from the vehicle during operation. The ESM1 is required to
be physically protected from wind and road splash using an enclosure box and/or thermal insulation for proper thermal
management of the device.

Water-cooled
Flange

Coolant
In Port

Air Inlet

High-voltage E-motor
with Integrated Inverter

Air Filter Housing
Identification
Nameplate

Sensor Wiring
Harness

Compressed
Air Outlet

Oil-coalescing
Filter

Rubber
Coolant Hose

Coolant
Out Port

Coupling

18 Bar
Safety Valve
Lifting Eyes
Oil Level
Sensor/Switch
Rotary Screw
Compressor

Oil Level
Port

Figure 1 – Electric Screw Module 1 (ESM1) Components

Oil Fill Port
Rotary Screw
Compressor
High-voltage
Amphenol Connector
for Power Supply

Vehicle Wiring
Connector

Oil Temperature
Sensor/Switch

The Bendix® Electric Screw Module 1 (ESM1) is a high-voltage device. Beware of electric shock. Service for the
ESM1 must be performed only by qualified technicians. The ESM1 has a high-voltage motor, and the motor should
not be opened or dismantled for repair. The ESM1 has air under high pressure within the rotary screw compressor,
and care must be taken when servicing the compressor to avoid sudden air pressure loss and/or hot oil expulsion,
which could result in injury.

IMPORTANT
The ESM1 has one (1) integral lifting eye on the compressor (18-mm diameter) and two (2) side M8 tapped holes on
the motor that allow lifting eyes to be screwed onto the device. Care should be taken to not tilt the ESM1 more than
45º during handling and installation to prevent oil spill.

MAINTENANCE
Maintenance must be performed every 1,500 operating hours (operating hours are defined as when the compressor is
running) or at least once a year.
• Change the oil (Chevron® Cetus® PAO 46 or
Castrol® Alphasyn T46 only)
•

Replace the oil-coalescing filter

•

Replace the air filter

• Visually check the compressor to track any potential
issues (leakages, shocks, etc.)

DIAGNOSTIC TROUBLE CODES (DTCS)
Use Bendix® ACom® PRO™ Diagnostic Software to read any potential Diagnostic Trouble Codes (DTCs) on the ESM1, and
take the appropriate next steps.

DTC CODE
(DEC)

257

260

261

262

DM1
AMBER
WARNING
LAMP

No

No

No

No

DM1 RED
WARNING
LAMP

Yes

Yes

Yes

Yes

NAME

eCompressor
(ESM1) fault:
Traction voltage
critically low, motor
stopped

eCompressor
(ESM1) fault:
Traction voltage
critically high,
motor stopped

eCompressor
(ESM1) fault:
Motor overload

eCompressor
(ESM1) fault:
Motor internal fault

DESCRIPTION

DC traction high voltage
supply malfunction: Voltage
lower than 420 V for 5
seconds, and the ESM1 is
requested to run.

DC traction high voltage
supply malfunction: Greater
than 800V for 0.5 seconds,
and the ESM1 is requested
to run.

DTC ACTION

•

Ensuring that all high-voltage precautions
and safety instructions are followed, check
the high-voltage DC supply to the ESM1.
Ensure that it is within specification of
500-800 VDC.

•

If the voltage being supplied to the ESM1
is out of specifications, contact the OEM for
further troubleshooting on the power supply
line.

•

Ensuring that all high-voltage precautions
and safety instructions are followed, check
the high-voltage DC supply to the ESM1.
Ensure that it is within specification of
500-800 VDC.

•

If the voltage being supplied to the ESM1
is out of specifications, contact the OEM for
further troubleshooting on power supply line.

•

Check the compressor air discharge line for
potential blocks due to ice or other reasons,
and clear any blockage if present. Ensure
there is free air flow to the air dryer.

•

If no blockage is found, check the oil level in
the compressor through the side level port.
CAUTION: Unscrewing the oil plug may
result in air pressure loss or hot oil spurting.
Ensure there is no air pressure within the
compressor by unscrewing for a half turn
and letting the system de-pressurize before
unscrewing completely. Refill if oil is needed.

•

If the previous steps do not resolve the
Diagnostic Trouble Code (DTC), the issue
could be a damaged motor or a damaged
compressor; replace the damaged
component.

•

Replace the ESM1 motor.

Motor overload, failed to
achieve >1400 RPM for 15
seconds continuously.

Motor internal fault - Power
stage error.

DTC CODE
(DEC)

DM1
AMBER
WARNING
LAMP

DM1 RED
WARNING
LAMP

NAME

263

No

Yes

eCompressor
(ESM1) fault:
Motor internal fault

264

265

No

No

Yes

Yes

eCompressor
(ESM1) fault:
Compressor
overheated

eCompressor
(ESM1) fault:
Motor overheated

DESCRIPTION

Motor internal fault - No
connection with power unit.

Compressor overheated.

DTC ACTION

•

Replace the ESM1 motor.

•

Turn off the device and allow the ESM1 to
cool down for approximately 60 minutes.

•

Ensure that there is proper coolant supply to
the ESM1. Coolant must be 50-50 ethylene
glycol-water mixture at nominal temperature
of 40ºC (104ºF) (should not go below 30ºC
[86ºF] or above 65ºC [149ºF]), with flow rate
of 10 l/min. Contact the OEM if the coolant
flow or temperature is not within specification.

•

Check the sensor wiring harness including
connectors and pins on the ESM1; replace
if faulty.

•

Check the thermal switch on the ESM1;
replace if faulty.

•

Check the oil level in the compressor through
the side level port. CAUTION: Unscrewing
the oil plug may result in air pressure
loss or hot oil spurting. Ensure there is
no air pressure within the compressor by
unscrewing for a half turn and letting the
system de-pressurize before unscrewing
completely. Refill if oil is needed.

•

Check the compressor air discharge line for
potential blocks due to ice or other reasons,
and clear any blockage if present. Ensure
there is free air flow to the air dryer.

•

If the problem persists, replace the
compressor.

•

Turn off the device and allow the ESM1 to
cool down for approximately 60 minutes.

•

Ensure that there is proper coolant supply to
the ESM1. Coolant must be 50-50 ethylene
glycol-water mixture at nominal temperature
of 40ºC (104ºF) (should not go below 30ºC
[86ºF] or above 65ºC [149ºF]), with flow rate
of 10 l/min. Contact the OEM if the coolant
flow or temperature is not within specification.

•

Check that the fan on the motor is working;
replace the motor if damaged.

•

Check the compressor air discharge line for
potential blocks due to ice or other reasons,
and clear any blockage if present. Ensure
there is free air flow to the air dryer.

•

If the problem persists, replace the motor.

Motor overheated.

DTC CODE
(DEC)

DM1
AMBER
WARNING
LAMP

DM1 RED
WARNING
LAMP

NAME

DESCRIPTION

DTC ACTION

•
270
272
273

268

271

276
277

No

Yes

Yes

Yes

Yes

No

No

No

eCompressor
(ESM1) fault: CAN
communication
error

eCompressor
(ESM1) fault:
Compressor oil
level low

eCompressor
(ESM1) fault: CAN