Bendix Commercial Vehicle Systems eTrac Automated Air Pressure Transfer System - Manual (Page 7)

7
SERVICING THE BENDIX ® ETRAC ™ SYSTEM
COMPONENTS
CAUTION: When replacing a Bendix eTrac-
enabled ECU, it is important to replace it ONLY with
another Bendix eTrac-enabled ECU as indicated by the
CAUTION label located on the ECU. Installation of a
non-eTrac-enabled ECU on an eTrac-equipped vehicle
can result in erroneous eTrac system interventions,
potentially causing vehicle damage and/or personal
injury.
NOTE: When replacing the valves used in this system,
it is important to replace ONLY like for like part numbers
(or direct replacement parts as verified by Bendix.) In
particular, the system’s upper pressure limit for the
drive axle suspension air bags is pre-determined by
the OEM, and this upper pressure limit determines the
specific Bendix RV‑3 valves that must be used to avoid
damage to the drive train.
NOTE: In the case of the valve used to backfeed in this
system, it is necessary to install the valve as shown
in the system diagrams, and not to follow the port
designations (such as SUP for supply, etc.) cast into
the valve housings.
See the specific Bendix
® Service Data Sheet for individual
components for maintenance information, including
leakage tests after re-installation.
ABS WIRING
When troubleshooting the ABS wiring used in this system,
some general rules should be followed where applicable.
1. Check all wiring and connectors to ensure they are
secure and free from visible damage (e.g. cuts,
abrasions, etc.).
2. Check for evidence of wire chafing due to poor routing,
or poor securing of wires.
3. Check connectors for proper insertion and locking.
4. Verify that the connector pins are properly greased with
a non-conductive electrical grease compound.
5. Connector terminals must not show signs of corrosion
or exposure to the environment.
6. Never pierce wire insulation when checking for
continuity.
7. Do not deform individual pins or sockets during probing
with a volt/ohm meter.
8. It is strongly recommended that all wiring harnesses and
sensor leads are properly secured at least every 18 inches.
9. Apply a moderate amount of non-conductive electrical
grease to each connector pin before reconnecting.
5. TROUBLESHOOTING
Since this system uses some familiar valves for special
purposes, the troubleshooting guide is presented in a
frequently-asked-questions format:
Q: The Bendix
® RV-3 ™ valve used for the backfeed function
seems to be incorrectly plumbed on the vehicle (and in
this document). Why?
A: To support special Bendix ® eTrac ™ system functions, it
is correct that the backfeed valve has its delivery port
connected to the leveling valve delivery port.
Q: What will happen if the backfeed valve’s supply is
connected to the leveling valve delivery?
A: An incorrectly installed backfeed valve will result in the
pressure-limiting function not working. The technician
may check if the backfeed function is working by
depressing the Mud/Snow switch on a fully loaded
vehicle; the vehicle’s tag axle should not drop down to
the suspension stops.
Q: How can I tell if the pressure-limiting function is
working?
A: With a fully loaded vehicle, depress the Mud/Snow
switch and verify that only a small amount of air is vented
(“dumped”) by the tag axle suspension air bags. The
tag axle bags should remain firm and the suspension
relatively level.
In the case of a vehicle that is running “bobtail” (without
a trailer), when the Mud/Snow switch is depressed,
verify that the tag axle bags become completely vented
(“dumped”).
Q: Why is the Bendix eTrac system not venting (“dumping”)
air pressure from the tag axle?
A: Inspect the exhausts of all the valves used in the Bendix
eTrac system to verify that they are free from debris.
Exhaust ports can develop blockages from ice, snow,
mud, or insects. Also check to see if the solenoid
valve is operating by listening for a clicking noise (as
the solenoid is energized) when the Mud/Snow switch
is activated. Note for vehicles with Bendix ® EC-80 ™
ATC/ESP ECUs: If the parking brake is set, the ability
to vent air pressure from the tag axle with the eTrac
feature is disabled.