Komatsu PC160LC-7 Fault Code E308: Complete Diagnostic Guide

What is Komatsu PC160LC-7 Fault Code E308?

Fault Code E308 on the Komatsu PC160LC-7 indicates a malfunction in the engine oil pressure sensor circuit or abnormally low engine oil pressure detected by the Electronic Control Module (ECM). This code specifically signals that the ECM has received either an out-of-range voltage signal from the oil pressure sensor or detected actual oil pressure below the manufacturer's minimum threshold during engine operation.

This fault is critical because the PC160LC-7's SAA6D102E-2 engine relies on precise oil pressure monitoring to prevent catastrophic engine damage. The ECM uses this sensor data to trigger protective shutdown sequences and alert operators before bearing failure, crankshaft scoring, or complete engine seizure occurs. In used excavators, this code often appears due to sensor degradation rather than actual lubrication system failure.

Common Symptoms

When Code E308 is active, operators typically experience:

• Illuminated engine oil pressure warning light on the dashboard (red oil can symbol)
• Audible alarm sounding continuously during operation
• Engine derate or automatic shutdown if pressure remains critically low
• Erratic oil pressure gauge readings fluctuating between normal and zero
• Hard starting or rough idle in conjunction with actual low pressure conditions

Potential Causes

The most common technical causes for E308 on used PC160LC-7 excavators include:

• Failed oil pressure sensor (diaphragm fatigue or internal electrical failure after 5,000+ hours)
• Damaged sensor wiring harness at known rub points near the engine mounting brackets
• Corroded or moisture-contaminated connector pins at the three-pin sensor plug
• Low engine oil level due to consumption or external leaks (valve cover gaskets common)
• Worn oil pump or clogged oil filter causing genuine pressure loss
• ECM voltage supply issues affecting sensor reference voltage (typically 5V supply circuit)
• Degraded engine oil with improper viscosity for operating temperature range

How to Troubleshoot and Fix Code E308

Step 1: Initial Verification Check actual engine oil level using the dipstick with the machine on level ground. Inspect for visible oil leaks around the oil filter housing, valve covers, and front crankshaft seal. If oil is low or contaminated, service before proceeding.

Step 2: Sensor Circuit Testing Locate the oil pressure sensor on the left side of the engine block near the oil filter. Disconnect the three-pin connector and inspect for corrosion, bent pins, or moisture—extremely common on used excavators stored outdoors. Using a digital multimeter, verify 5V reference voltage on the signal wire (typically gray wire) with ignition on, engine off.

Step 3: Sensor Resistance Check Measure sensor resistance between the signal and ground pins. The factory specification for the PC160LC-7 sensor is approximately 40-60 ohms at room temperature when unpressurized. Readings outside this range indicate sensor failure requiring replacement (Komatsu part number 7861-93-1650).

Step 4: Wiring Harness Inspection Trace the sensor harness back to the ECM connector (approximately 2 meters), checking for wire chafing at the engine mount bracket and fuel filter mounting points—known wear locations. Use the multimeter's continuity function to verify no open circuits and insulation resistance testing to check for shorts to ground.

Step 5: Mechanical Pressure Verification If electrical tests pass, install a mechanical oil pressure gauge in the sensor port. Run the engine at operating temperature and verify pressure meets specifications: minimum 71 psi (490 kPa) at rated RPM. Low mechanical pressure indicates oil pump wear, bearing clearance issues, or pressure relief valve malfunction.

Step 6: Final Verification After repairs, clear codes using Komatsu diagnostic software (KOMTRAX PC or compatible scan tool). Operate the excavator through a full work cycle, monitoring oil pressure under load to confirm the fix.

For used excavators, always check connector sealing and harness routing before replacing expensive components like the ECM or oil pump.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu PC160LC-7 service manual and consider professional diagnostic assistance for complex engine issues. Improper diagnosis can lead to costly part replacement or engine damage.