
94 RENR9348-01
Troubleshooting Section
Expected Result:
The diagnostic code deactivates when a particular
sensor is disconnected.
Results:
•
OK – The 262-03
or 262-04 diagnostic
code deactivates when a particular sensor is
disconnected.
Repair: Connect the suspect sensor. If the code
returns, replace the sensor. Connect all of the
connectors.
Verify that the problem is resolved.
STOP.
•
Not OK – The 262-03 or 262-04 diagnostic
code remains active after all of the sensors are
disconnecte
d.Thesensorsarenotthecauseofthe
diagnostic code. Leave the sensors disconnected.
Proceed to Test Step 4.
Test Step 4. Check the Supply Voltage at
the ECM
A. Disconnect
the J2/P2 ECM connectors.
B. Fabricate two jumper wires that are long enough
to be used as
test leads at the ECM connectors.
Crimp connector sockets to one end of each
jumper wire.
C. Remove the wires from terminal locations P2-72
(5 V sensor supply) and P2-17 (sensor return).
Install a j
umper wire into each of these terminal
locations.
D. Connect th
e J2/P2 ECM connectors.
E. Restore electrical power to the ECM.
F. Measure the voltage between the jumper wire in
P2-72 (5 V sensor supply) and the jumper wire in
P2-17 (se
nsor return).
G. Remove electrical power from the ECM.
Expected Result:
The volta
ge measurement is 5.0 ± 0.2 VDC.
Results:
•
OK – The voltage measurement is 5.0 ± 0.2 VDC.
The ECM is operating correctly.
Repair: There is a problem in the engine harness.
The problem may
be with a connector. Repair the
harness and/or the connector. Replace parts, if
necessary. Verify that the problem is resolved.
STOP.
•
Not OK – The vol
tage measurement is not 5.0 ±
0.2 VDC.
Repair: There
is a problem with the ECM. Replace
the ECM. Refer to Troubleshooting, “Replacing
the ECM”.
STOP.
i02419268
Air Shutoff System - Test
SMCS Code: 10
78-038
System Operation Description:
Use this procedure to troubleshoot any problems with
the air shutoff system.
The Electronic Control Module (ECM) has the ability
to stop the engine in an emergency situation by
shutting of
f the air supply to the engine. The ECM
activates a relay which energizes two air shutoff
solenoids. The solenoids trip the air shutoff valves.
There are three conditions which can cause the ECM
to activate the air shutoff:
Engine Overspeed – The first condition occurs
when the ECM detects an engine overspeed. During
an engine o
verspeed, the ECM energizes the air
shutoff relay. The ECM supplies voltage to the air
shutoff relay for one second. The output of the relay
will energ
ize the air shutoff solenoids in order to
shut down the engine. Once an event for the air
shutof f system is activated, the event is latched until
electric
al power to the ECM system is cycled.
Overspeed Verify Feature – The second condition
occurs wh
en the overspeed verify feature is initiated
with Caterpillar Electronic Technician (ET). This
feature will energize the air shutoff relay when the
engine s
peed is increased above 75 percent of the
rated engine speed. The ECM supplies voltage to the
air shutoff relay for one second during the shutdown.
The over
speed verify feature can be initiated in order
to test the operation of the air shutoff system.