INJECTOR AS-FUEL 1265970 - 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
Illustration 3 g00676834
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
Illustration 4 g00676466
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
Illustration 5 g00676834
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
Illustration 6 g00676466
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
Illustration 7 g00676466
J1/P1 breakout
Illustration 8 g00676834
J2/P2 breakout
Start the engine. Ensure that the keyswitch