Spicer CTIS (Central Tire Inflation System) Troubleshooting Guide - Manual (Page 51)

48
Service Codes
Display
Control
Communications (Code 75)
Display Control Communications (Code 75)
Yes
Turn on ignition.
Is
driver interface
completely
blank?
With vehicle running, measure battery
voltage across battery terminals.
Base vehicle power is out of range.
Refer to Service Manual
Does
measured
voltage match
battery voltage reading
obtained
in previous
step?
Repair harness POWER or
GROUND connections to
driver interface.
Replace DDM.
Switch ignition off.
Disconnect ECU connector.
Disconnect DDM connector.
Are voltages within range?
Inspect fuses/
repair harness
to power ECU.
Is there continuity?
Inspect and repair
faulty
communications
circuit in harness.
Is any circuit shorted?
Inspect and
repair faulty
wire or
connection.
Replace DDM.
Switch on ignition.
Is driver
interface functioning
correctly?
Complete
With ignition switched on but engine
not running, measure battery
voltage across battery terminals.
Is voltage
reading >32
volts?
Is voltage
reading <9
volts?
Disconnect DDM.
With ignition on, measure
voltage between:
DDM Display Harness Pins
4 and 5
Base vehicle power is out of range.
Refer to Service Manual
Check continuity between:
ECU and DDM Display
Harness Pin Harness Pin
J3 6
K3 7
Check for communication circuits shorted to GROUND,
POWER or shorted to each other. Check between:
DDM Display Harness Pins
6 and 4
7 and 4
7 and 5
6 and 5
6 and 7
No
No
Yes
No
Yes
Yes
No
No
Yes
No
Yes
Yes
No
No Yes
Replace ECU.
Note: ECUs are not a typical cause of
problems. If an ECU is replaced, the
system should be carefully rechecked
to make sure the problem has been
fixed and does not reoccur.
Switch ignition on.
Verify adequate voltage (18-32 Vdc) between:
ECU Harness Connector Pins
POWER (K1) and GROUND (A3)
SWIGN (C3)* and GROUND (A3)
* Only on systems with separate SWIGN.