336 7 ELECTRONIC CONTROL SYSTEMS DIAGNOSTICS
Brake Shut-off Valve Circuit Operation
Figure 397 Brake S hut-off Valve circuit diagram
The brake shut-off valve is supplied ground to Pin 1
from the batter y through Pin 4 of the 12-pin conne c tor
and then through Pin A of the valve cover gasket. The
ECM controls the engine brake by supplying 12 volts
through Pin C of the valve cover gasket to Pin 2 of the
brake shut-off valve.
Fault Detection / Management
An open or short to ground in the brake shut-off valve
control circuit can be detected by an on demand
Output Circuit Check (OCC) during KOEO Standard
Test. If there is a circuit fau lt d etec te d a DTC will be
set.
When the engine is running, the ECM compares
engine brake control pressure to injection control
pressure and BCP desired. When the brake is
activated, brake control pressure will equal injection
control pressure.
If the brake control pressure does not match injection
control p ressure, the ECM will disable the engine
brake, a DTC will be set, and the amber ENGINE
lamp will be illuminated.
When the engine brake is not active and the ECM
detects an undesired value, the ECM will set a DTC
and the ambe r E NGINE lamp w ill be illuminated.
A bias BCP sensor can also cause the fault. The brake
shut-off valve and the BCP sensor circuit should both
be diagnosed.
Brake Shut-off Valve Diagnostic Trouble Codes
(DTCs)
DTCs are read using the EST or by counting the
flashes from the amber and red ENGINE lamp.
DTC 247
Engine brake enable OCC self-test failed
• DTC 247 is set by the ECM when the OCC test
has failed after the KOEO Standard Test has been
run.
• DTC 247 can be set when a poor connection,
an open or short to ground in the brake shut-off
valve c o n tro l circuit, or a failed brake s hu t-off
valve solenoid exists.
EGES-270-1
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
Follow all warnings, cautions, and notes.
© August 2008 Navistar, Inc.
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