“Komatsu SAA4D95LE Engine Troubleshooting: Step‑by‑Step Diagnostic Guide”

ECU Sensors Used in Komatsu SAA6D107 / SAA6D114 Diesel Engine

The Komatsu SAA6D107 and SAA6D114 engines use an electronically controlled common-rail system. Their ECU depends on multiple sensors to manage fuel injection, rail pressure, turbo boost, emissions, and engine protection. If any sensor sends incorrect data, the ECU may activate warning lights, derate mode, or engine shutdown.

Overview of ECU Sensors

Sensor	Main Function	ECU Use
Crankshaft Position Sensor (CKP)	Detects engine speed & crank position	Starting, injection timing
Camshaft Position Sensor (CMP)	Identifies cylinder phase	Injection sequence
Fuel Rail Pressure Sensor	Measures rail pressure	Controls injection quantity
Fuel Temperature Sensor	Monitors fuel temperature	Fuel density compensation
MAP / Boost Pressure Sensor	Measures intake manifold pressure	Turbo control, AFR
Intake Air Temperature Sensor (IAT)	Measures air temperature	Cold start & emissions
Coolant Temperature Sensor (ECT)	Monitors coolant temperature	Fan, glow plugs, enrichment
Exhaust Gas Temperature Sensor (EGT)	Monitors exhaust temperature	Turbo & emission protection
Accelerator Pedal Position Sensor (APP)	Reads pedal position	Electronic throttle
Oil Pressure Sensor	Monitors lubrication pressure	Engine protection
Ambient Air Pressure Sensor	Detects atmospheric pressure	Altitude compensation
Knock Sensor (if equipped)	Detects abnormal combustion	Timing adjustment

1. Crankshaft Position Sensor (CKP)

Location: Flywheel housing

Function:

• Detects engine speed (RPM)
• Provides crank position for injection timing

Failure Symptoms:

• No start
• No RPM signal
• Engine shutdown

2. Camshaft Position Sensor (CMP)

Location: Cylinder head

Function:

• Identifies cylinder phase
• Synchronizes injection

Failure Symptoms:

• Hard starting
• Misfire
• Irregular idle

3. Fuel Rail Pressure Sensor

Location: Common rail

Function:

• Measures rail pressure
• Controls injector duration

Failure Symptoms:

• Stalling
• No start
• Derate mode

4. Fuel Temperature Sensor

Location: Fuel rail or supply line

Function:

• Monitors fuel temperature
• Adjusts fueling for density

Failure Symptoms:

• Power loss
• Incorrect fueling
• Derate

5. Intake Air Pressure Sensor (MAP / Boost)

Location: Intake manifold

Function:

• Measures boost pressure
• Controls turbo & AFR

Failure Symptoms:

• Low boost
• Black smoke
• Low power

6. Intake Air Temperature Sensor (IAT)

Location: Intake pipe

Function:

• Measures incoming air temperature
• Improves cold start

Failure Symptoms:

• Poor cold start
• High fuel consumption

7. Engine Coolant Temperature Sensor (ECT)

Location: Block / thermostat housing

Function:

• Monitors coolant temperature
• Controls fan & glow plugs

Failure Symptoms:

• Overheating warning
• White smoke
• Fan always running

8. Exhaust Gas Temperature Sensor (EGT)

Location: Exhaust manifold / turbo outlet

Function:

• Protects turbo
• Controls emissions

Failure Symptoms:

• Derate
• High EGT alarm

9. Accelerator Pedal Position Sensor (APP)

Location: Pedal assembly

Function:

• Sends throttle command
• Controls engine speed

Failure Symptoms:

• No throttle response
• Stuck idle
• Limp mode

10. Oil Pressure Sensor

Location: Oil gallery

Function:

• Monitors lubrication pressure
• Prevents engine damage

Failure Symptoms:

• Low oil warning
• Engine shutdown

11. Ambient Air Pressure Sensor

Location: ECU housing / intake

Function:

• Adjusts fueling for altitude

Failure Symptoms:

• Power loss at altitude

12. Knock Sensor (If Equipped)

Location: Engine block

Function:

• Detects abnormal combustion

Failure Symptoms:

• Reduced power
• Timing retard

Common ECU Reactions

Condition	ECU Reaction	Outcome
Critical sensor failure	Shutdown	Engine stops
Incorrect readings	Derate	Limited power
Missing signal	Fallback value	Reduced performance

Conclusion

The Komatsu SAA6D107 and SAA6D114 engines rely on a precise network of ECU sensors. Understanding each sensor’s location, function, and failure symptoms helps technicians diagnose faults faster, reduce downtime, and avoid unnecessary parts replacement.

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