Mitsubishi S12A2 Engine

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Fault codes

Symptoms & remedies

Fault codes and symptom→remedy steps extracted from this engine’s service/owner documentation; verify against the official manual before servicing.

• White or blue exhaust smoke
  Cause: Too much oil in crankcase; Oil viscosity too low; Engine overcooled; Thermostat defective (low water temperature); Injection timing incorrect; Compression pressure low
  Fix: Fill only to correct level on gauge; Refill with correct viscosity of oil; Use radiator cover, or clean, test and replace thermostat; Replace; Readjust; Disassemble and replace parts
• Water pump defective
  Fix: Replace.
• Too low oil level
  Fix: Maintain oil level in operating range on gauge.
• Thermostat defective
  Fix: Replace.
• Starters will not crank engine or crank slowly, resulting in a failure of engine to start
  Cause: Electrical system: Battery — starter switch circuit open; Starters, starter relay defective
  Fix: Repair or replace; Adjust alternator drive belt
• Starter will crank engine, but engine will not start
  Cause: Fuel system: Fuel tank filled; Fuel leaks from pipe; Wrong type of fuel; Dirt or water in fuel; Battery specific gravity low; Electrical system: Alternator drive belt adjustment required; Fuel filters clogged; Circuit defective; Injection pumps defective; Air cleaners clogged; Engine proper: Running parts defective, interference between pistons, foreign matter in cylinder
  Fix: Refill with correct type of fuel; Clean or repair fuel filters; Replace; Adjust alternator drive belt; Consult Mitsubishi dealer
• Radiator or heat exchanger dirty
  Fix: Wash.
• Lack of coolant
  Fix: Refill.
• High oil consumption
  Cause: Too high oil level in crankcase
  Fix: Maintain oil level in operating range on gauge.
• High fuel consumption
  Cause: Injection pumps defective; Injection nozzles defective; Injection timing incorrect; Wrong type of fuel
  Fix: Disassemble and replace parts; Clean or repair injection nozzles; Readjust; Refill with correct type of fuel
• Fan belt loose
  Fix: Readjust.
• Engine lacks power
  Cause: Incorrect grade of oil; Wrong type of fuel; Insufficient air (air cleaner clogged); Engine overcooled; Engine overheating; Valve clearance incorrect; Injection pumps defective; Injection nozzles defective; Injection timing incorrect; Compression pressure low (cylinders and pistons worn)
  Fix: Use recommended type and SAE number of oil; Change; Clean or change element; Use radiator cover, replace parts; Flush cooling system or replace parts; Readjust; Readjust or replace; Readjust or replace; Disassemble and replace parts
• Compression pressure low
  Cause: Insufficient air
  Fix: Readjust or replace.
• Black or gray exhaust smoke
  Cause: Wrong type of fuel; Valve clearance incorrect; Injection pumps defective; Compression pressure low; Insufficient air (air cleaners clogged); Turbocharger defective
  Fix: Refill with correct type of fuel; Readjust; Disassemble and replace parts; Clean or change elements; Disassemble and replace parts

Compiled from service & troubleshooting documentation across every generator set that uses the Mitsubishi S12A2.

Pooled from every document that names this exact engine — confirm the interval and part number against your unit's serial number.

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Parts cataloged across all variants of this engine family — verify the exact part fits your specific variant and serial number before ordering.

Parts listed by aftermarket suppliers as fitting this engine — leads compiled from supplier catalogs; verify the exact part for your serial number.

• Hitachi EX1900-5 — Excavator Tracked

Other equipment known to use this engine, via filter-application cross-reference — useful for sourcing parts even when your exact machine isn't listed elsewhere on this page.