Description

Komatsu PC158US-2 2004 Workshop Manual

I’ve been turning wrenches for 28 years. ASE Master. Six bays in San Antonio. I’ve seen what happens when a guy trusts an aftermarket manual for a Komatsu excavator. Stripped threads, blown seals, hours of backtracking. That’s why I’ll tell you straight: if you’re working on a Komatsu PC158US-2 2004 Workshop Manual is the only document you should have on your bench. This is the OEM publication, printed by Komatsu in 2004, and it runs 521 pages. No reprints. No photocopies. This is the same manual the dealer techs use.

You get the full structure: General specs (page 01-1), Structure and Function (10-1), Testing and Adjusting (20-1), Disassembly and Assembly (30-1), Maintenance Standard (40-1), and Others (90-1). Every torque value, every clearance, every hydraulic pressure comes straight from the factory. Want to adjust valve clearance on that S4D102E-1 engine? It’s in section 20 under “ADJUSTING VALVE CLEARANCE.” Need the standard value table for chassis? Look at “STANDARD VALUE TABLE FOR CHASSIS.” You’re not guessing. You’re following the path Komatsu laid out.

Valve Clearance and Engine Adjustments

The manual dedicates a full page to Valve clearance adjustment. It tells you the exact feeler gauge thickness (cold), the sequence to follow, and the torque on the locknut. No generic “tighten until snug.” You get in-lb specs. I’ve had half a dozen techs come through my shop who thought they could skip this step on a hydraulic excavator. They ended up with a ticking engine that lost power under load. This manual stops that before it starts. The procedure is listed under “TESTING AND ADJUSTING” section, right after measuring exhaust color and blow-by pressure. You also get the standard value table for engine parameters—oil pressure, compression, injection timing. All factory figures.

Hydraulic System: PC-EPC Valve and Control Valve

If you’ve ever chased a sluggish swing or weak travel on a PC158US-2, you know the hydraulic system is the heart of the machine. The manual covers the entire hydraulic component layout: PC-EPC Valve, Control Valve, CLSS, Self Pressure Reducing Valve, Center Swivel Joint, Travel Motor, Swing Motor. For the PC-EPC system, there’s a dedicated troubleshooting section (E-1) with two fault trees: (a) all work equipment, travel, swing are slow or lack power, and (b) excessive drop in engine speed or engine stalls. Each tree gives you step-by-step electrical checks and hydraulic pressure tests. You test output pressure of the PC valve (servo piston input pressure) using the tools listed on the “TOOLS FOR TESTING, ADJUSTING AND TROUBLESHOOTING” page. You get the exact psi ranges at rated engine speed. I’ve used those numbers to diagnose a bad PC-EPC solenoid in under 20 minutes. No wasted time.

Testing and Adjusting: 7 Critical Procedures

Section 20 is where the real work happens. It’s not a list of suggestions—it’s a sequence of events. Start with measuring engine speed (requires a tachometer with a specific adapter). Then move to exhaust color (use the opacity chart provided). Then adjust valve clearance. Then fuel injection timing. Then belt tension for the AC compressor. The manual doesn’t assume you know the order. It lays out the “SEQUENCE OF EVENTS IN TROUBLESHOOTING” explicitly. If you skip ahead, you miss the step that bleeds remaining pressure from the hydraulic circuit—and that step can save you from a face full of hot oil. The manual even includes a “PROCEDURE FOR CHECKING DIODE” so you don’t blow a controller board with a backprobe.

Does This Manual Cover the Fuel System?

Yes. The engine section includes “TESTING AND ADJUSTING FUEL INJECTION TIMING” with timing marks and injection pump specifications. You also get the fuel control cable adjustment and engine stop solenoid linkage inspection. The manual covers the S4D102E-1 engine in depth—referencing the separate 102 Series Engine Shop Manual for internal rebuilds, but the chassis-specific fuel system adjustments are all here. If you need injector pump timing, you’ll find it next to the valve clearance procedure. No flipping between manuals for crossover data.

Source Validity: OEM vs Aftermarket

I’ve been burned by aftermarket manuals. They mix up pinouts, guess at torque values, or leave out critical safety warnings. This Komatsu PC158US-2 Workshop Manual is a direct scan of the original SEBM026504 publication. The front page states “This shop manual may contain attachments and optional equipment that are not available in your area. Please consult your local Komatsu distributor.” That’s OEM language. The binding mark table on page 00-2 confirms revision control. Pages are marked with letters to show new, replaced, or deleted sections. That level of traceability doesn’t exist in a generic PDF farm product. If you want to trust your work, trust the source that built the machine.

Is this the full 521-page manual or a shortened version?

Full manual. All 521 pages, including the cover and list of revised pages. You get the complete Table of Contents, all sections (General, Structure/Function, Testing/Adjusting, Disassembly/Assembly, Maintenance Standard, Others), and the troubleshooting section with connector arrangement diagrams. No missing pages.

What about the electrical system? Are the wiring diagrams included?

Yes. Section 20 includes a “CONNECTOR ARRANGEMENT DIAGRAM,” “CONNECTION TABLE FOR CONNECTOR PIN NUMBERS,” “T-BRANCH BOX AND T-BRANCH TABLE,” and “RELATED ELECTRICAL CIRCUIT DIAGRAMS FOR ELECTRICAL SYSTEM.” The troubleshooting charts for the controller and electrical system cover PC-EPC, PPC lock solenoid, swing lock solenoid, travel speed solenoid, running speed auto change, and engine starting system. Each fault has step-by-step diagnosis. You need a multimeter and a breakout box for some tests, but the manual tells you exactly which pins, which resistance, which voltage. If you’ve ever wired a diode backwards because the aftermarket diagram was mirrored—this manual prevents that.

If you’re serious about working on a Komatsu PC158US-2, don’t waste time with third-party copies that blur the torque specs. Access the Factory Manual from AutoRepairManuals. You’ll get the same 521-page document that Komatsu issued in 2004. Print out the pages you need for the job, leave the greasy fingerprints on the bench, and know that every number on that page is factory-approved. I’ve got a copy in my own shop reference binder. It’s the difference between a repair that holds and one that comes back on a hook.

• Komatsu WA65-5 WA70-5 WA80-5 2005 Workshop Manual”>Related: Komatsu WA65-5 WA70-5 WA80-5 2005 Workshop Manual
• Komatsu WH609-1E0 WH613-1E0 WH713-1E0 WH714H-1E0 WH716-1E0 Workshop Manual”>Related: Komatsu WH609-1E0 WH613-1E0 WH713-1E0 WH714H-1E0 WH716-1E0 Workshop Manual
• Komatsu PW95R-2 Workshop Manual – 520 Pages of Factory Specs”>Related: Komatsu PW95R-2 Workshop Manual – 520 Pages of Factory Specs

Manual Transmission”>Manual Transmission – Not directly related but a reference for general driveline knowledge. Manual Transmission”>Manual Transmission – Another general resource.