MBE 900 DDEC VI Troubleshooting – Section 121.1 SPN 3659/FMI 6

Section 121.1
SPN 3659/FMI 6

This diagnosis is typically the Electronic Unit Pump Cylinder #1, Circuit Shorted to Battery.‪

1. Turn ignition OFF.
2. Disconnect the MCM 120-pin connector.
3. Using the J-48475 Breakout Box and J-48583 overlay, connect the MCM side of the harness ONLY.
4. Turn ignition ON.
5. Measure the voltage between pin 14 of the J-48475 Breakout box and ground.
   1. If voltage is greater than 0.5v, contact CSC for MCM replacement.
      

      Figure 1. Electronic Unit Pump #1

   2. If voltage is present, repair short to power between pin 14 of the MCM 120-pin connector See Figure "Electronic Unit Pump #1" and the Electronic Unit Pump Cylinder #1 .