Komatsu PC160LC-7 Fault Code S-5: Complete Diagnostic Guide

What is Komatsu PC160LC-7 Fault Code S-5?

Fault Code S-5 on the Komatsu PC160LC-7 indicates a malfunction in the engine oil pressure switch circuit or abnormally low engine oil pressure detected by the monitoring system. This code is triggered when the Electronic Control Module (ECM) receives an irregular signal from the oil pressure sensor or detects that oil pressure has fallen below the manufacturer's safe operating threshold.

This fault is critical because inadequate oil pressure can lead to catastrophic engine damage through insufficient lubrication of bearings, pistons, and other internal components. The Komatsu SAA4D107E-1 engine in the PC160LC-7 requires consistent oil pressure (typically 2.5-4.5 kg/cm² at rated speed) to maintain proper lubrication and cooling of critical engine parts.

Common Symptoms

When Code S-5 is active, operators typically experience:

• Engine warning light illuminated on the instrument panel, often accompanied by an audible alarm
• Automatic engine derate or shutdown in protective mode to prevent damage
• Oil pressure gauge reading lower than normal operating range (below 1.0 kg/cm²)
• Rough idling or unusual engine noise, particularly a ticking or knocking sound from the valve train
• Reduced hydraulic performance due to engine speed limitations imposed by safety protocols

Potential Causes

The most common technical causes for S-5 on used PC160LC-7 excavators include:

• Faulty oil pressure sensor/switch – The sensor (part #6732-81-3140) commonly fails after 5,000+ operating hours due to heat cycling and oil contamination
• Low engine oil level – Leaks from worn valve cover gaskets, oil pan, or hydraulic pump seals
• Wiring harness damage – Chafing at the firewall pass-through or near the engine mount points causes intermittent short circuits
• Clogged oil filter or screen – Restricted flow from extended service intervals or contaminated oil
• Worn oil pump – Internal wear reduces pressure output, especially common in machines exceeding 8,000 hours
• Corroded or loose electrical connectors – The 3-pin connector at the oil pressure sensor oxidizes in harsh environments

How to Troubleshoot and Fix Code S-5

Step 1: Verify Actual Oil Pressure Check the physical oil level with the dipstick on level ground. If low, fill to specification and monitor for leaks. Install a mechanical oil pressure gauge at the test port (located near the oil filter) to verify actual pressure versus sensor reading. At operating temperature and rated RPM, pressure should read 3.5-4.5 kg/cm².

Step 2: Inspect the Oil Pressure Sensor and Wiring Locate the oil pressure switch on the left side of the engine block near the oil filter housing. Disconnect the 3-pin connector and inspect for corrosion, oil intrusion, or pushed-back pins. Use a multimeter to check sensor resistance: with the engine off, resistance should be infinite (open circuit); with oil pressure applied, it should drop to near zero ohms. Check wiring continuity from the sensor back to ECM pin A-18 for opens or shorts to ground.

Step 3: Test Electrical Signal to ECM Using Komatsu diagnostic software (KOMTRAX) or an aftermarket scan tool compatible with Komatsu proprietary protocols, monitor live oil pressure sensor voltage. Normal signal voltage ranges from 0.5V (low pressure) to 4.5V (high pressure). If voltage remains constant regardless of engine speed or shows erratic spikes, replace the sensor. Before replacing, clean the sensor mounting threads and apply anti-seize compound to prevent galvanic corrosion.

Step 4: Inspect Oil System Components (Used Machine Specific) On used excavators, remove the oil pan and inspect the oil pump pickup screen for debris or sludge buildup. Check the oil pump drive gear for excessive wear (more than 0.15mm clearance). Examine main and rod bearings for scoring – excessive clearances allow pressure bleed-off. Replace the oil filter with OEM Komatsu parts (600-211-1340) to ensure proper bypass valve operation.

Step 5: Address Harness Issues Common to This Model The PC160LC-7 is known for harness rubbing where the engine loom passes through the bulkhead near the left-hand cab mount. Inspect for worn insulation and repair with proper high-temperature electrical tape and protective loom. Secure the harness away from sharp edges and heat sources.

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Disclaimer: This guide provides general troubleshooting procedures for the Komatsu PC160LC-7. Always consult the official Komatsu service manual and consider professional diagnostic services for complex repairs. Improper repairs may void warranties or cause equipment damage.