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Mack Diagnostic Trouble Code – 1761

Details

 

  • Park vehicle on level surface, turn ignition OFF, set parking brake and block wheels.
  • Connect scan tool, turn ignition ON with engine OFF and record all circuit related active and inactive fault codes. Turn ignition OFF. If any codes are Voltage Supply Codes, Diagnose these codes first. Go to step 15. If no Voltage Supply Codes exist, go to next step.
    NOTE: If multiple active fault codes are present a shared open or shorted supply, return, or ground circuit is possible.
  • Verify there is no visible damage to components. Ensure correct DEF Tank fluid level. Repair/replace faulty components; go to step 16. If components are good go to next step.
  • Disconnect ACM connector and inspect wiring harness connectors and Terminals for damage, moisture, proper Terminal tension, and corrosion. If damage is found, clean and repair as required. Go to step 15. If no damage is found, go to next step.
     
  • Disconnect Diesel Exhaust Fluid (DEF) Level Sensor harness connector and inspect wiring harness connectors and Terminals for damage, moisture, proper Terminal tension, and corrosion. If damage is found, clean and repair as required. Go to step 15. If no damage is found, go to next step.
     
  • Connect ACM connector. Disconnect Diesel Exhaust Fluid (DEF) Level Sensor harness connector. Turn ignition ON. Measure voltage between Diesel Exhaust Fluid (DEF) Level Sensor harness connector voltage supply circuit Terminal 1 and component return circuit Terminal 4. Record voltage measurement. Turn ignition OFF. If voltage is 5 Volts, replace sensor. Go to step 15. If voltage is NOT 5 Volts, go to next step.
    NOTE: Measure towards ACM.
  • Disconnect ACM connector. Turn ignition ON. At ACM, measure voltage between Voltage Supply Terminal A50 and Return Terminal A54. Record voltage measurement, turn ignition OFF. If voltage is 5 Volts, go to next step. If voltage is NOT 5 Volts, contact an authorized OEM service center to verify a possible ACM malfunction. Go to step 15.
    NOTE: Measure towards ACM.
  • With ACM connector and Diesel Exhaust Fluid (DEF) Level Sensor harness connector disconnected, measure sensor resistance between Diesel Exhaust Fluid (DEF) Level Sensor Signal Terminal 2 and Voltage Supply Terminal 1 of sensor connector. Verify resistance is 10 Ohms. If resistance is NOT 10 Ohms, clean/replace sensor. Go to step 15. If resistance is 10 Ohms, go to next step.
    NOTE: Measure towards sensor.
  • With ACM connector and Diesel Exhaust Fluid (DEF) Level Sensor harness connector disconnected, measure sensor resistance between Diesel Exhaust Fluid (DEF) Level Sensor Signal Terminal 2 and Ground Terminal 4 of sensor connector; verify resistance is 10 Ohms. If resistance is NOT 10 Ohms clean/replace sensor. Go to step 15. If resistance is 10 Ohms, go to next step.
    NOTE: Measure towards sensor.
  • With ACM connector and Diesel Exhaust Fluid (DEF) Level Sensor harness connector disconnected, measure resistance between Diesel Exhaust Fluid (DEF) Level Sensor Signal Circuit Terminal 2 harness connector and a good ground. Repeat this step for Diesel Exhaust Fluid (DEF) Level Sensor harness connector voltage supply Terminal 1 and Return Circuit Terminal 4. If resistance is less than 100K Ohms repair short to ground. Go to step 15. If resistance is more than 100K Ohms go to next step.
    NOTE: Measure towards ACM.
  • With ACM connector and Diesel Exhaust Fluid (DEF) Level Sensor harness connector disconnected, measure signal circuit resistance between ACM Diesel Exhaust Fluid (DEF) Level Sensor Signal Circuit Terminal A46 in harness connector and Diesel Exhaust Fluid (DEF) Level Sensor Terminal 2 in sensor harness connector. If resistance is more than 10 Ohms repair or replace open circuit or excessive resistance in harness, go to step 15. If resistance is less than 10 Ohms go to next step.
    NOTE: Measure across harness.
  • With ACM connector and Diesel Exhaust Fluid (DEF) Level Sensor harness connector disconnected, measure signal circuit resistance between ACM Diesel Exhaust Fluid (DEF) Level Sensor Supply Terminal A50 in harness connector and Diesel Exhaust Fluid (DEF) Level Sensor Terminal 1 in sensor harness connector. If resistance is more than 10 Ohms repair or replace open circuit or excessive resistance in harness, go to step 15. If resistance is less than 10 Ohms go to next step.
    NOTE: Measure across harness.
  • With ACM connector and Diesel Exhaust Fluid (DEF) Level Sensor harness connector disconnected, measure return circuit resistance between ACM Diesel Exhaust Fluid (DEF) Level Sensor Return Terminal A54 in harness connector and Diesel Exhaust Fluid (DEF) Level Sensor Terminal 4 in sensor harness connector. If resistance is more than 10 Ohms repair or replace open circuit or excessive resistance in harness, go to step 15. If resistance is less than 10 Ohms go to next step.
    NOTE: Measure across harness.
  • With ACM connector and Diesel Exhaust Fluid (DEF) Level Sensor harness connector disconnected, measure signal circuit resistance between ACM Voltage Supply Terminal A50 and all other Terminals on ACM Harness connector. Measure return circuit resistance between ACM Return Terminal A54 and all other Terminals on same ACM Harness connector. Verify resistance is 10 Ohms. If resistance is NOT 10 Ohms repair short in harness and go to step 15. If resistance is 10 Ohms go to next step.
    NOTE: Measure towards harness.
  • Connect ACM and Diesel Exhaust Fluid (DEF) Level Sensor harness connectors, go to next step.
  • Clear fault codes and verify code is NOT active. If code is still active, repeat diagnostics to verify diagnostics were performed correctly. If code is still active, contact an authorized OEM service center to verify a possible ECM malfunction.

 

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