Diagnose This! What the beep?

Each month in Diagnose This! we present a real-life service scenario with clues as to what the ultimate diagnosis was. If you think you know the answer, be the first to e-mail dsmith@rrpub.com with the correct response for free Truck Parts & Service merchandise. The answer will be revealed in a future issue of the magazine.

This month’s Diagnose This! is submitted by ASE master technician and owner of Fleet Guardian, Damon Russell.

If you have a Diagnose This! puzzler you would like to submit, please send it to dsmith@rrpub.com.

Vehicle: 2005 International 4400 tractor

Key components: Allison HT570 automatic transmission, air brakes

Scenario: This municipal vehicle’s city horn beeps exactly twice every time the ignition key is turned to the “run” position.


  • The vehicle is unmodified from the OEM configuration.
  • No added warning devices or theft prevention exist on the vehicle.
  • The city horn does not work when the horn pad is depressed.
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