
166 RENR9348-01
Troubleshooting Section
1. Check the voltage between engine ground and
the following t
est points. If voltage is not present
at a test point, the problem is in the device, in
the wire or in the connector that precedes the
point in the ci
rcuit.RefertoIllustration94asa
reference.
Table 22
Device Test location
Battery +Battery terminal
Starting motor +Battery terminal
Input terminal
Auxiliary breaker
Output terminal
Engine interface connector
Term ina l 4
2. Measure the voltage between the battery’s
+Battery terminal and the following test points.
If voltage is not present at a test point, the
problem is in the device, in the wire or in the
connector that precedes the point in the circuit.
RefertoIllustration94asareference.
Table 23
Device Test location
Input terminal
Battery disconnect switch
Output terminal
Starting motor −Battery terminal
Engine interface connector Terminal 39
Repair the circuit or replace the device that is
causing the problem.
If a problem with the batteries is suspected, refer
to the diagnostic functional test Operating Manual,
SEHS9249 and Special Instruction, SEHS7633 for
information that is related to testing the batteries.
STOP.
Test Step 3. Check the Status for the
Throttle Position on Caterpillar Electronic
Technician (ET)
A. Connect Cat ET to the service tool connector.
Observe the status parameter for the throttle
position on Cat ET.
B. Restore electrical power to the ECM.
C. Turn the speed adjust potentiometer to the lowest
setting.
D. Adjust the speed adjust potentiometer from the
lowest setting
to the highest setting. Monitor the
statusforthethrottlepositiononCatETwhileyou
perform the test.
E. Remove electrical power from the ECM.
Expected Resu
lt:
The throttle position on Cat ET changes proportionally
as the speed ad
just potentiometer is adjusted.
Results:
•
OK – The speed control is operating correctly.
Repair: There
may be an intermittent problem in a
harness or a connector. If an intermittent problem
is suspected, refer to Troubleshooting, “Inspecting
Electrical C
onnectors” for troubleshooting
information.
STOP.
•
Not OK – The throttle position on Cat ET does not
vary as the s
peed adjust potentiometer is adjusted.
There is a problem in the circuit between the speed
control and the ECM. Proceed to Test Step 4.
Test Step 4. Check the PWM Signal at the
Speed Control
A. Remove the w
ires from terminal locations 19
(+PWM out) and 20 (−PWM out) at the speed
control.
B. Use a multimeter that is capable of reading a
percent duty cycle in order to measure the output
at termina
l locations 19 and 20 at the speed
control.
C. Restore e
lectrical power to the ECM.
D. Monitor the output of the percent duty cycle from
the termi
nal locations at the speed control on the
multimeter. Turn the speed adjust potentiometer
from the low setting to the high setting.
E. Remove electrical power from the ECM.
Restore t
he wiring to the original configuration.
Expected Result:
The duty cycle changes as the speed adjust
potentiometer is adjusted.
Results:
•
OK – The th
rottle signal is present at the speed
control. Proceed to Test Step 5.