Yanmar 4BY - Engine Coolant Temperature Sensor; Fuel Rail Pressure Control Valve

ELECTRICAL AND ECU
BY Service Manual
12-17
Component Tests
Engine Coolant Temperature Sensor
This sensor measures the temperature of the
engine coolant. It is a NTC (negative temperature
coefficient) type sensor. It is mounted in the
cylinder head.
The sensor output is used by the ECU for:
• Calculation of the injection rate
• Regulating glow plug on-time
• Regulating engine low idle speed
• Regulating fuel rail pressure
Results of Failed Sensor
Failure of the sensor results in:
• Destruction of the sensor if short circuit to B+
If this sensor is defective, the following P-codes
may be generated:
• P0117 - short circuit to B+
• P0118 - No connection / short to ground
Test Values
• Resistance at 20°C (68°F): 2.5 - 3.0 k-ohm
• Resistance at 50°C (122°F): 0.7 - 0.9 k-ohm
• Resistance at 100°C (212°F): 0.12 - 0.17 k-ohm
Figure 12-11
1 – Pin 1 - Out (ECU pin 1/82)
2 – Pin 2 - Ground (ECU pin 1/7)
Fuel Rail Pressure Control Valve
This valve controls the fuel pressure in the fuel rail.
The ECU uses values supplied by several sensors
and sends corresponding signals to control fuel
pressure. It is mounted on the rear of the fuel rail.
Results of Failed Valve
Failure of the valve results in:
• Limitation of the injection rate (See Engine Faults
and Torque Limitations on page 13-3.)
• Engine may fail to start
IMPORTANT
If a fault code is set, check the fuel supply
and delivery first!
If this valve is defective, the following P-codes may
be generated:
• P0088 - fuel rail pressure out of range
• P0087 - fuel rail pressure out of range
• P0089 - fuel rail pressure out of range
• P0090 - not connected / valve failure
• P0091 - short circuit to ground / valve failure
• P0092 - short circuit to B+ / valve failure
Test Values
• Resistance at 20°C (68°F): 4.0 ohm
• At 1800 bar (26, 107 psi) (relative): 4.5 V
Figure 12-12
1 – Pin 1 - 12V (Fuse F5)
2 – Pin 2 - Out (ECU pin 1/72)
0004168
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0004169
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