
134 RENR9348-01
Troubleshooting Section
g01159881
Illustration 64
Sensor co nnector
(A) Se nsor supply
(B)Sensorreturn
(C) Sens or signal
C. Perform a 45 N (10 lb) pull test on each of the
wires in the ECM connector and on each of the
wires in the pressure sensor connectors.
D. Check the allen head screw for each of the
ECM connectors and the customer connector
for the proper torque. Refer to Troubleshooting,
“Electrical Connectors - Inspect” for the correct
torque values.
E. Check the harness and wiring for abrasions and
for pinch points from each of the pressure sensors
back to the ECM.
Expected Result:
All connectors, pins, and sockets are completely
coupled and/or inserted. The harness and wiring are
free of corrosion, of abrasion, and of pinch points.
Results:
•
OK – The harness and wiring appear to be OK.
Proceed to Test Step 2.
•
Not OK – There is a problem in the connectors
and/or wiring.
Repair: Repair the connectors or wiring and/or
replace the connectors or wiring. Ensure that
all of the seals for each of the connectors are
properly in place and ensure that the connectors
are completely coupled. Verify that the repair
eliminates the problem.
STOP.
Test Step 2. Check the Supply Voltage at
the Sensor Connector
A. Remove electrical power from the ECM.
B. Disconnect th
e harness connectors for the
following sensors:
•
Atmospheric p
ressure sensor
•
Intake manifold pressure sensor
•
Engine oil pressure sensor
•
Fuel pressure
sensor
C. Restore electrical power to the ECM.
Note: The original diagnostic code may not stay
active. An open circuit diagnostic code for the sensor
supply may be
come active when all of the sensors
are disconnected. Ignore the active codes at this time
and continue with this test step.
Note: Be sure to wiggle the harness during the
following measurements in order to reveal an
intermitte
nt condition.
D. Measure the voltage between terminals A and B
at each sens
or connector on the engine harness.
E. Remove electrical power from the ECM.
F. Connect all of the sensors.
Expected Re
sult:
Each voltage measurement is 5.0 ± 0.2 VDC.
Results:
•
OK –Eachvol
tage measurement is 5.0 ± 0.2 VDC.
The voltage is correct at the sensor connectors.
ProceedtoTestStep3.
•
Not OK – The voltage is not 5.0 ± 0.2 VDC.
Repair: The
voltage is incorrect. There may be a
problem with the sensor supply circuit. Refer to
Troubleshooting, “5 Volt Engine Pressure Sensor
Supply Cir
cuit - Test” for information that is related
to troubleshooting the circuit.
STOP.
Test Step 3. Check fo r Active Diagnostic
Codes
A. Connect Caterpillar Electronic Technician (ET) to
the service tool connector.