Table 2. Engine Troubleshooting with Codes for the 120M Motor Grader - Continued.
CDI FMI CODE
N OT E
1779-06 Fuel Rail #1 Pres-
sure Valve Solenoid Current
The Engine ECM uses data from the fuel pressure sensor to control a
Above Normal - Continued
solenoid in the pump in order to maintain the desired fuel pressure in
the rail. Excess fuel returns to the fuel tank through a one-way return
valve. The fuel injection pump is not serviceable. Only personnel that
have had the correct training should adjust pump timing.
The fuel injection pump solenoid co trol circuit Y950-YL starts at engine
ECM harness connector EA-C1 terminal 25 and is routed to fuel rail
pump solenoid harness connector EA-C2 terminal 1. The solenoid
ground circuit starts at fuel rail pump solenoid harness connector EA-
C2 terminal 2 and is routed to the engine ECM harness connector EA-
C1 terminal 26.
Test Step 1. Verify Diagnostic Code
N OT E
Always inspect the harness connectorsthat are involved in the circuit.
Poor connections can often be the cause of a problem in an electrical
circuit. Verify that all connections in the circuit are clean and secure,
and that all connections are in good condition. If a problem with a
connection is found, correct the problem and verify that this diagnostic
code is active before performing this procedure.
Perform open or short circuit test ateach harness connection to identify
correct harness to replace.
Perform this test only if condition is active.
1. Perform Fuel Rail Pump Solenoid Diagnostic code 1779-06 Active -
Test (WP 0035) and check if diag- Proceed to Test Step 2.
nostic code 1779-06 becomes
Test Step 2. Test Solenoid Control
1. Turn the ignition switch to the
2. Disconnect harness connector
fuel rail pump solenoid.
3. Turn ignition switch to the ON
4. Perform Fuel Rail Pump Solenoid
1779-06 Remains Active - Proceed
Test (WP 0035) and check if diag-
to step 5.
nostic code 1779-05 becomes
1779-05 Becomes Active - ECM and
circuits test OK, fuel rail pump
solenoid faulty. Replace fuel injection
pump (WP 0074).