TUBE AS 3082117 - Caterpillar

3176 Truck Engines, 3406B (PEEC) Truck EnginesUndesired engine shutdown has been caused by auxiliary power applications of 3176 and 3406B (PEEC) Truck Engines using the idle shutdown timer feature. This article explains how the addition of a switch in the parking brake circuit can solve this problem.
The idle shutdown timer is meant to cut down on unnecessary idle time by shutting off the engine after a specified idle time. Once the parking brake is set and no vehicle speed is detected, the Electronic Control Module (ECM) will allow the engine to idle for a specified time and then shut off the engine if the parking brake remains set. However, the engine may need to remain idling in some applications to run auxiliary power functions such as a DC motor or hydraulic pumps.
This problem can be corrected by inserting a switch in series with the parking brake circuit so that the circuit is open when the auxiliary power function is ON. When the parking brake circuit is open, the idle shutdown timer is disabled. For example, a DPDT (Double Pole Double Throw) switch could be used as the ON/OFF switch to a DC motor. See either Illustration 1 or 2. One of the two DPDT contacts should be connected to the 12 volt auxiliary application supply. The other DPDT switch contact should then be placed in series with the parking brake switch as shown in the illustrations. This contact is wired in such a way that the parking brake circuit is open when the auxiliary is switched ON, thus disabling the idle shutdown timer.
Illustration 1. 3176 Truck Engine with modified parking brake circuit using DPDT switch.
Illustration 2. 3406B (PEEC) Truck Engine with modified parking brake circuit using DPDT switch.As a second example, a pressure switch could be installed in a hydraulic line. See either illustration 3 or 4. The switch contacts would open the parking brake circuit when pressure exists in the hydraulic lines thus disabling the idle shutdown timer.
Illustration 3. 3176 Truck Engine with modified parking brake circuit using pressure switch.
Illustration 4. 3406B (PEEC) Truck Engine with modified parking brake circuit using pressure switch.