Case IH 398 – Engine Control Module (ECM): Rear Timing current is too low

The Engine Control Module (ECM) has detected an abnormally low electrical current (or an open circuit) on the circuit controlling the Rear Timing Actuator, which is a critical solenoid located on the Cummins Accumulator Pump System (CAPS) fuel injection pump.

• MX Magnum
• STX Steiger
• MX240
• MX255
• MX270
• MX275
• MX285
• STX275
• STX325
• 2366
• 2377
• 2388
• 2577
• 2588
• SPX4410
• 4420

1. 1

   Inspect the engine wiring harness running from the ECM to the CAPS pump for chafed wires, melted insulation, or breaks

2. 2

   Disconnect the electrical connector at the CAPS pump and the ECM to check for pushed-back pins, moisture, or corrosion

3. 3

   Measure the resistance across the pins for the rear timing actuator on the CAPS pump using a multimeter to check for an open circuit or out-of-spec reading

4. 4

   Check the transient suppressor diode, as a failed suppressor often leads to actuator failure

1. 1

   Disconnect Power

   Disconnect the negative battery cables to prevent electrical shorts.

2. 2

   Clean the Area

   Thoroughly clean the engine area around the CAPS pump to prevent dirt from entering the open fuel system.

3. 3

   Remove Fuel Lines

   Disconnect the low-pressure supply lines and the high-pressure fuel lines from the pump. Cap all open fittings immediately.

4. 4

   Disconnect Electronics

   Unplug the main electrical harness from the CAPS pump.

5. 5

   Remove the Pump

   Unbolt the CAPS pump from the engine gear housing and carefully remove it.

6. 6

   Install the New Pump

   Mount the remanufactured CAPS pump, ensuring the gear timing aligns perfectly according to the engine service manual. Torque mounting bolts to spec.

7. 7

   Replace the Transient Suppressor

   Always install a new transient suppressor diode when replacing a CAPS pump. Failure to do so can cause electrical spikes that will immediately destroy the new pump's actuators.

8. 8

   Reassembly

   Reconnect all fuel lines and electrical connectors.

9. 9

   Prime and Clear

   Reconnect the batteries, bleed the air from the fuel system, start the engine, and use a diagnostic tool to clear the inactive fault code 398.