What causes low power in the Mercedes Actros OM471 engine?

Low power is usually caused by boost leaks, turbo actuator faults, clogged fuel filters, injector issues, or DPF blockage.

How do I diagnose low power in the OM471?

Start by scanning ECU fault codes, checking boost pressure, fuel rail pressure, and inspecting intake and exhaust restrictions.

What are the most common OM471 fault codes for low power?

Common codes include P2263, P2459, P0401, P0087, P0106, and P20EE.

Can a faulty turbo actuator cause low power?

Yes. A malfunctioning VGT actuator prevents proper turbo vane movement, reducing boost.

How do I check for a boost leak on the OM471?

Perform a pressure test on the charge-air system and inspect hoses, clamps, and the intercooler.

Does a clogged DPF reduce engine power?

Yes. A blocked DPF increases exhaust backpressure and severely limits power.

What are the symptoms of a bad MAP sensor on the OM471?

Symptoms include limp mode, low boost, incorrect readings, and a check engine light.

Can dirty fuel filters cause low power?

Yes. Restricted fuel flow reduces rail pressure and engine performance.

How often should OM471 fuel filters be replaced?

Typically every 20,000–30,000 km, depending on fuel quality and operating conditions.

What happens if the EGR valve sticks open?

It reduces oxygen supply, causing black smoke, rough idle, and low power.

How do I know if the high-pressure fuel pump is failing?

Look for hard starting, low rail pressure, and fault codes related to fuel delivery.

Can injector problems cause low power in the OM471?

Yes. Worn or leaking injectors disrupt fuel delivery and combustion efficiency.

What are signs of a boost pressure sensor failure?

Unstable readings, limp mode, low boost, and fault codes like P0106.

Does valve timing affect power on the OM471?

Incorrect timing or a worn timing chain reduces torque and overall performance.

How do I fix low power caused by a blocked air filter?

Replace the air filter and inspect intake ducts for collapse or blockage.

Can poor-quality diesel fuel cause low power?

Yes. Contaminated fuel clogs filters and damages injectors.

How do I perform a forced DPF regeneration on the OM471?

Use a diagnostic tool to initiate regeneration and monitor exhaust temperatures.

What should I check first when the OM471 enters limp mode?

Scan for fault codes, then inspect boost pressure and sensor readings.

Can a cracked intercooler cause low power?

Yes. It reduces boost pressure and increases intake air temperature.

How do I prevent low power issues on the OM471?

Follow regular maintenance: replace filters, inspect hoses, monitor DPF health, and use high-quality diesel.

Komatsu SPN/FMI Error Code Table for ECU Sensor Faults

Komatsu SPN / FMI Error Code Reference (ECU Sensor Faults)

Komatsu machines use the SAE J1939 SPN/FMI diagnostic standard. The following table lists the most common Komatsu engine‑related sensor faults along with symptoms and descriptions.

Komatsu diagnostic flowchart showing SPN/FMI troubleshooting steps including wiring check, sensor test, and fault resolution.

Common Komatsu Engine SPN/FMI Codes

SPN	FMI	Sensor / System	Fault Description	Typical Symptoms
84	3	Accelerator Pedal Position Sensor	Voltage above normal	High RPM, erratic throttle
84	4	Accelerator Pedal Position Sensor	Voltage below normal	No throttle response, limp mode
91	3	Accelerator Pedal Sensor	Signal too high	Sudden RPM increase
91	4	Accelerator Pedal Sensor	Signal too low	Engine stuck at idle
94	3	Fuel Delivery Pressure	Pressure above normal	Black smoke, rough running
94	4	Fuel Delivery Pressure	Pressure below normal	Hard start, stalling
100	3	Oil Pressure Sensor	Voltage above normal	False oil pressure alarm
100	4	Oil Pressure Sensor	Voltage below normal	Engine shutdown protection
110	3	Coolant Temperature Sensor	Temperature too high	Overheat alarm, fan always ON
110	4	Coolant Temperature Sensor	Temperature too low	Cold start smoke, slow warm‑up
157	3	Fuel Rail Pressure Sensor	Rail pressure too high	Engine knock, derate
157	4	Fuel Rail Pressure Sensor	Rail pressure too low	Crank‑no‑start
190	3	Crankshaft Speed Sensor	RPM signal too high	Unstable RPM
190	8	Crankshaft Speed Sensor	Signal missing	Cranks but will not start
102	3	Intake Manifold Pressure (Boost)	Pressure too high	Turbo overboost
102	4	Intake Manifold Pressure (Boost)	Pressure too low	Power loss, black smoke
105	3	Intake Air Temperature Sensor	Signal above normal	Poor fuel economy
105	4	Intake Air Temperature Sensor	Signal below normal	Hard cold starting
175	3	Fuel Temperature Sensor	Temperature too high	Engine derate
175	4	Fuel Temperature Sensor	Temperature too low	Rough running
723	9	Glow Plug Control System	Data valid but abnormal	Hard cold start, white smoke

FMI Code Meaning (Quick Guide)

FMI	Meaning
0	Data valid – no fault
3	Voltage above normal
4	Voltage below normal
7	Mechanical system not responding
8	Signal missing
9	Data valid but abnormal
14	Signal erratic or intermittent

Quick Troubleshooting Tips

SPN 190 FMI 8 → Check crankshaft sensor gap, connector, and harness
SPN 157 FMI 4 → Inspect rail pressure, suction leaks, and fuel supply
SPN 110 FMI 3/4 → Verify coolant level, thermostat, and sensor resistance
SPN 84 FMI 3/4 → Recalibrate or replace accelerator pedal sensor

Why This Table Helps Technicians

Faster and more accurate fault identification
Reduces unnecessary parts replacement
Minimizes machine downtime
Improves diagnostic accuracy

Electrical engineering

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