FAN AS-COOLING 3728533 - Caterpillar

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Front engine view
(10) Secondary speed/timing sensor
(11) Primary speed/timing sensor
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Rear engine view
(12) P2 ECM connector
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Terminal locations at the P2 ECM connector that are for the engine speed/timing sensors
(P2-25) Primary engine speed/timing signal (−)
(P2-35) Primary engine speed/timing signal (+)
(P2-46) Secondary engine speed/timing signal (+)
(P2-47) Secondary engine speed/timing signal (−)
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Connector for the engine speed/timing sensors
(Terminal 1) Speed/timing sensor (−)
(Terminal 2) Speed/timing sensor (+)
Table 4
Troubleshooting Test Steps Expected Result Results
3. Inspect the Electrical Connectors and the Wiring
A. Remove the electrical power from the ECM.
B. Thoroughly inspect connectors (10), (11), and (12). Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
C. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit for the engine speed/timing sensor.
D. Check the allen head screw for each ECM connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect".
E. Check the harness and wiring for abrasion and for pinch points from the engine speed/timing sensors to the ECM.
All connectors, pins, and sockets are coupled and/or inserted. The harness and wiring are free of corrosion, of abrasion, and of pinch points.
Result: The harness and the wiring appear to be OK. Proceed to Test Step 2.
Result: 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 the connectors are properly in place and ensure that the connectors are coupled. Verify that the repair eliminates the problem.
STOP
4. Measure the Sensor Resistance through the Engine Harness
A. Remove the electrical power from the ECM.
B. Disconnect the P2 connector.
C. Perform the following procedure in order to measure the resistance of the primary engine speed/timing sensor:
1. Measure the resistance from P2-35 (primary engine speed/timing +) to P2-25 (primary engine speed/timing -).
Resistance ... 1000 to 1200 Ohms
D. Perform the following procedure in order to measure the resistance of the secondary engine speed/timing sensor:
1. Measure the resistance from P2-46 (secondary engine speed/timing +) to P2-47 (secondary engine speed/timing -).
Resistance ... 1000 to 1200 Ohms
The resistance measurements are within the specifications.
Result: The resistance measurements are within the specifications.
Repair: The sensors and the harness are OK. There is a problem with the ECM. Replace the ECM. Refer to Troubleshooting, "ECM - Replace" for details.
STOP
Result: The readings are not within the specifications. The sensor resistance is not within the acceptable range when the sensor resistance is measured through the engine harness. Proceed to Test Step 5.
5. Measure the Resistance of the Sensor
A. Disconnect the engine harness from