SUPPORT-FRONT 2596217 - Caterpillar

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ECM connector P1
Disconnect ECM connector J1/P1.
Disconnect fan speed sensor connector J84/P84.
Measure the resistance between P1:35 (Digital Sensor +8 VDC) and chassis ground.
Measure the resistance between P1:35 (Digital Sensor +8 VDC) and P1:29 (Digital Sensor Return).
Measure the resistance between P2:25 (Fan Speed Sensor) and P1:29 (Digital Sensor Return).
Measure the resistance between P1:35 (Digital Sensor +8 VDC) and P2:25 (Fan Speed Sensor).Expected Result:The resistance for each measurement should be greater than 20,000 Ohms.Results:
OK - Proceed to Test Step 6.
Not OK - There is a short between the ECM and the fan speed sensor.Repair: Repair the circuit.STOPTest Step 5. Check for Shorts in the Harness From the Fan Speed Sensor to ECM Connector J2/P2
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ECM connector P2
Disconnect ECM connector J2/P2.
Disconnect fan speed sensor connector J84/P84.
Measure the resistance between P2:25 (Fan Speed Sensor) and chassis ground.
Measure the resistance between P2:25 (Fan Speed Sensor) and P1:29 (Digital Sensor Return).
Measure the resistance between P1:35 (Digital Sensor +8 VDC) and P2:25 (Fan Speed Sensor).Expected Result:The resistance for each measurement should be greater than 20,000 Ohms.Results:
OK - Proceed to Test Step 7.
Not OK - There is a short between the ECM and the fan speed sensor.Repair: Repair the circuit.STOPTest Step 6. Check for Open Circuits in the Harness From the Fan Speed Sensor to ECM Connector J1/P1
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J1/P1 breakout
Turn the keyswitch to the OFF/RESET position and install a 7X-1715 Adapter Cable (40 Pin Breakout) at ECM connector J1/P1.
Use a suitable piece of wire to short P1:35 (Digital Sensor +8 VDC) and P1:29 (Digital Return) at the breakout.
Disconnect fan speed sensor connector J84/P84.
Measure the resistance between P84:A (+8 VDC) and P84:B (Ground).Expected Result:The resistance should be less than 10 Ohms.Results:
OK - Proceed to Test Step 8.
Not OK - There is an open circuit in the wiring harness between the fan speed sensor and the ECM.Repair: Repair the circuit.Verify that the repair eliminates the problem.STOPTest Step 7. Check for Open Circuits in the Harness From the Fan Speed Sensor to ECM Connector J2/P2
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ECM connector P2
Disconnect ECM connector J2/P2.
Disconnect fan speed sensor connector J84/P84.
Measure the resistance between P84:C (Signal) and P2:25 (Engine Fan Speed).Expected Result:The resistance should be less than 8 Ohms.Results:
OK - Proceed to Test Step 8.
Not OK - There is an open circuit in the wiring harness between the fan speed sensor and the ECM.Repair: Repair the circuit.Verify that the repair eliminates the problem.STOPTest Step 8. Check the Digital Sensor Supply Voltage at the ECM
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J1/P1 breakout
Turn the keyswitch to the ON position.
Measure the voltage across P1:35 (Digital Sensor +8 VDC) and P1:29 (Digital Return) at the breakout.Expected Result:The digital sensor supply voltage should be 8.0 0.5 VDC.Results:
OK - The ECM is producing a valid supply voltage. Proceed to Test Step 9.
Not OK - The ECM may not be producing a valid supply voltage.Repair: Verify your results.Replace the ECM. Refer to Troubleshooting, "Replacing the ECM" before replacing the ECM.Verify that the repair eliminates the problem.STOPTest Step 9. Check the Signal Frequency at the ECM
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J1/P1 breakout
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J2/P2 breakout
Start the engine. Ensure that the keyswitch