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Understanding & Diagnosing Kubota SCR Intermediate Harness Sequence

 

 

SEQUENCE OF OPERATION

1. Power available at Main Relay – CKTS 810 & 909

2. Key Switch ON

     a. CN6E-26 turns ON and provides power to Safety Relay

     b. Power provided to SPLICE 7

           i. CN6E-2 CKT 805D powers up

           ii. ECU CNTRL Relay – CKT 914 via 5A fuse CN4-A10/B10

           iii. WAIT TO START signal – CN6E-7/CKT 907A

           iv. START Relay – CN4-D4 /CKT-805B

 

 

3. Upper Control System “Wake Up”

     a. CN6E-16 to GND (CKT 908)

     b. ECU Relay Energizes;

           i. Power to NEUTRAL Relay POS of Coil – CKT 914C

           ii. Power to ECU – CKT 914B

                1. ECU “ON” and sends GROUND to Main Relay – CN4-F6/CKT 922

                2. ECU & Accessory Power Up

                     a. ECU Full Power Up – CKT 906A & SPLICE 1

                           i. CKT 926 – 10A fuse CN4-C10/D10 – NOx/DEF Sensors

                           ii. CKT 926A Power Up – Alternator Ignition

                           iii. CKT 926B – ECU Main Power

                           iv. CKT 916 – WIF Sensor & Fuel Pump

 

4. Machine in Neutral

     a. CN6E-11 GROUND at CN4-F2 causes NEUTRAL Relay to Energize

     b. Upper Level Control System broadcasts NEUTRAL and PARK Message over CAN.

 

5. Key Switch to Start

     a. Start Signal from KEY-50 passes through 5A Fuse CN4-C9/D9

     b. Signal passes through NEUTRAL Relay CN4-D2/F1 via CKT 905B to SPLICE 13

           i. CKT 905D sends start input to ECU via CN17-11

           ii. CKT 909A energizes START relay at CN4-D3

           iii. ECU controls Starter Relay NEG of Coil to prevent starter overrun.

 

 

 

 

 

 

 

 

 

 

 

 

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