This checklist outlines some general hints and guidelines that will be helpful in tracking down and correcting operating
4The ECU only displays one active code.
Only the most recent service code displays on the ECU
lights. In troubleshooting, be alert for related codes.
Use of a diagnostic tool offers the advantage of spotting
multiple active codes as well as retrieving historical
4A cleared code alone does not indicate a corrected
A code is set by a specific fault condition and may be
cleared by switching the ignition off, and then on. It's
possible to clear a code (i.e., clear the flashing lights)
only to have it display again when the fault condition
reoccurs. To insure that a problem is fixed, you must
run the system through the same operating modes that
caused the problem and verify that the service code
does not reappear.
4Electrical faults are often connection problems.
The most likely cause of electrical faults will be damaged
wires or connections. As a first step in troubleshooting
all electrical codes, switch off vehicle ignition, then
damage. (Switching off the ignition is required before
disconnecting the harness at the Electronic Control Unit,
but is also a recommended practice before all other
electrical system disconnections.) Clean or repair all bad
connections before proceeding.
4Disconnect the Electronic Control Unit connector
with ignition off.
To avoid setting electrical fault codes, make sure that
the ignition is off before unplugging the wire harness
connection at the Electronic Control Unit module.
Reconnect the connector before switching on the
4System is not continually pressurized.
When troubleshooting pneumatic faults, keep in mind
that the air system is only pressurized as needed (for
example, in the inflate mode).
This means that such procedures as checking for leaks
require the system to be in an active, pressurized state.
This can be accomplished most easily by using a
4Basic vehicle air and power systems are not
covered in this guide.
The Central Tire Inflation System requires air pressure
and electrical power supply from the base vehicle
systems. Diagnosis and service of these systems is
located elsewhere in this manual.
4Some faults will halt inflate or deflate sequence.
Upon sensing some faults, the Central Tire Inflation
System will immediately go to the "maintain" mode. This
may cause the mode light to stop flashing before the
system has actually attained the pressures for the
Change 3 3-92.15