Kohler 15ROY troubleshooting: 10 fault codes and 214 symptom-cause-remedy entries from the manufacturer's own service documentation.
Kohler 15ROY — full specs, parts & maintenance.
| Code | Meaning | Cause |
|---|---|---|
| BLOWN F1 FUSE (REMOTE ANNUNCIATOR-3 AMP) | Blown controller fuse F1 | DEFECTIVE DECISION DEFECTIVE MONITOR (IF EQUIPPED) REMOTE ANNUNCIATOR (IF EQUIPPED) DEFECTIVE REMAINING ACCESSORIES AUDIO-VISUAL CONNECTED TO TB1-42A ALARM (IF EQUIPPED) |
| BLOWN F2 FUSE (CONTROLLER-3 AMP) | Blown controller fuse F2 | BATTERY CONNECTIONS REVERSED SHORTED DC SUPPLY TO INDICATOR PANEL SHORTED CONTROLLER CIRCUIT BOARD |
| LOP | Low Oil Pressure (LOP) Shutdown | |
| HET | High Engine Temperature (HET) Shutdown | |
| LWL | Low Water Level (LWL) Shutdown | |
| 36 | High Engine Temperature | |
| 38 | Low Oil Pressure | |
| OC | Overcrank | |
| OS | Overspeed | |
| LOWT | Low Water Temperature |
| Symptom | Cause | Remedy |
|---|---|---|
| No output | Blown fuse on CSA models (fuses on sensing leads V7, V8 and V9 protect regulator board and SCR module against an overcurrent condition) | |
| No output | Fault in the Automatic Voltage Regulation (AVR) circuit (output available when separately excited) | |
| No output | Shorted or open rotor | Replace rotor |
| No output | Running short in the rotor (ammeter current increases considerably when separately excited) | Replace rotor |
| No output | Open rotor (ammeter current drops to zero when separately excited) | Replace rotor |
| No output | Faulty stator winding (no output from any winding) | Repair or replace stator |
| No output | Weak brush springs, loose holder, sticking brushes or improper brush-to-slip ring alignment causing brushes to wear excessively or unevenly | Repair or replace brush assembly |
| No output | No continuity between quick disconnect point on brush lead and its adjacent slip ring | Repair or replace assembly |
| No output | Faulty SCR module (ohmmeter checks indicate faulty SCR module) | Replace SCR module |
| No output | Faulty regulator board (regulator board test indicates faulty regulator board) | Replace regulator board and refer to new board adjustment procedure |
| No output (RZ models) | No voltage present across F3 and F4 | Check controller |
| No output (RZ models) | Current high or low at F3 (ammeter should read 4/10 of 1 amp) | Check exciter field |
| No output (RZ models) | No voltage at L1, L2, L3, V7, V8, V9, VO and V4 (should read 25-35 volts) | Refer to No Output checks |
| Generator set will not crank | Blown 10 amp fuse inside the controller | Replace the fuse and attempt to restart generator set; if the set will not start, or if the fuse blows again, locate and correct the cause |
| Generator set stops | Blown 10 amp fuse inside the controller (short develops in the wiring) | Replace the fuse and attempt to restart generator set; if the set will not start, or if the fuse blows again, locate and correct the cause |
| Generator set will not crank | Blown 15-amp fuse (protects CR and 1CR relay contacts from overcurrent in the event of a short in the wiring or engine accessories) | |
| Generator set shuts down while running | 15-amp fuse blows while the generator set is running | |
| SWITCH OFF lamp on controller does not flash | Switch and harness connections | Check switch and harness connections; replace uni-board; repeat test |
| Other lamps do not light when LAMP TEST button is pushed | Blown 3 amp fuse at rear of controller and/or burned out bulbs | Check/replace 3 amp fuse at rear of controller, and/or replace bulbs as needed |
| IGN., CRK., and REG. lamps of Fast Check do not light (CRK. should light for around 10 seconds) | Wiring to 1CR | Check wiring to 1CR; replace uni-board; repeat test |
| CRK. lamp alone does not light (voltage not conducted to starter circuit) | Uni-board or 1CR relay wiring/relay | Replace uni-board; fix 1CR relay wiring or replace relay; repeat test |
| IGN. or REG. lamps do not light | Uni-board or CR relay wiring/relay | Replace uni-board; fix CR relay wiring or replace relay; repeat test |
| After second cranking cycle, IGN., CRK. and REG. lamps do not go out and OVERCRANK lamp on controller plus A.D. and ALARM lamps on Fast Check do not light | Uni-board | Replace uni-board; repeat test |
| Cyclic cranking does not stop after 45-75 seconds | Cranking cycle adjustment | Try adjustment; repeat test; replace uni-board |
| CRK. lamp does not go out when Fast Check engine switch is moved to RUN | 1CR relay and wiring | Check 1CR relay and wiring; replace uni-board; repeat test |
| Unit will not crank | Weak or dead battery | Recharge or replace battery |
| Unit will not crank | Reversed or poor battery connections | Check connections |
| Unit will not crank | Defective starter/starter solenoid | Rebuild or replace |
| Unit will not crank | Defective start/stop switch (local or remote) | Test function; replace if defective |
| Unit will not crank | Fuse blown in controller | Replace fuse; if fuse blows again, check circuit and components |
| Unit will not crank | Open in wiring, terminals, pin, circuit board, etc. | Check continuity |
| Unit will not crank | Defective circuit board | Check circuit board operation |
| Unit will not crank | Overcrank shutdown | Check engine fuel supply. Shutdown occurs after 30 seconds of continuous cranking (relay controller) or 45 seconds of continuous cranking or 75 seconds of cyclic cranking (5-light controller). Cyclic cranking available on 5-Light Microprocessor Controller only. |
| Cranks but will not start | Out of fuel | Replenish fuel supply |
| Cranks but will not start | Air cleaner clogged | Clean or replace filter element |
| Cranks but will not start | Defective fuel solenoid | Test fuel solenoid |
| Cranks but will not start | Defective fuel pump | Test fuel pump |
| Cranks but will not start | Clogged fuel filter | Replace fuel filter |
| Cranks but will not start | Air in fuel system | Bleed air from system |
| Cranks but will not start | Bad fuel mixture | Replace fuel |
| Cranks but will not start | Water, dirt in fuel system | Drain, flush fuel system |
| Cranks but will not start | Dirty, faulty fuel injectors | Clean/repair injectors |
| Cranks but will not start | Faulty ground (-) connection | Clean and re-tighten |
| Cranks but will not start | Weak or dead battery | Recharge or replace |
| Cranks but will not start | Poor engine compression | |
| Cranks but will not start | Blown voltage regulator fuse | Replace fuse |
| Cranks but will not start | Oil viscosity too heavy for ambient temperature | |
| Cranks but will not start | Defective controller circuit board | |
| Cranks but will not start | Open in wiring, terminals, pin, circuit board, etc. | Check continuity |
| Engine knocks | Faulty fuel injector(s) | |
| Engine knocks | Air in fuel injectors | Bleed air from system |
| Engine knocks | Improper fuel | Use proper fuel; consult fuel supplier |
| Engine knocks | Incorrect fuel injection timing | |
| Engine knocks | Improper cylinder top clearance | Check clearance |
| Engine knocks | Defective piston pin bearing | |
| Engine knocks | Defective crankshaft bearing or piston pin bearing | |
| Engine knocks | Improper valve clearance | |
| Starter motor does not work properly | Loose or corroded connections | Clean and tighten connections |
| Starter motor does not work properly | Battery not fully charged | Check battery electrolyte level and specific gravity. Recharge battery if necessary |
| Starter motor does not work properly | Defective starter solenoid | Test starter solenoid. Replace solenoid, if required |
| Starter motor does not work properly | Defective starter motor | Rebuild or replace starter motor |
| Starter motor does not work properly | Engine lube oil viscosity too heavy for ambient temperature | Use proper viscosity oil |
| Starter motor does not work properly | Defective start/stop switch | Test/replace switch |
| Starter motor does not work properly | Defective wiring | Check wiring |
| Starter motor does not work properly | Battery cables undersize | Select proper size cable |
| Engine runs irregularly or stalls frequently | Vent in fuel tank obstructed | Remove obstruction |
| Engine runs irregularly or stalls frequently | Clogged fuel filter | Replace fuel filter element |
| Engine runs irregularly or stalls frequently | Water, dirt, or air in fuel system | Drain, flush, bleed fuel system |
| Engine runs irregularly or stalls frequently | Dirty or faulty fuel injectors | Clean/repair injectors |
| Engine runs irregularly or stalls frequently | Faulty governor linkage or governor incorrectly adjusted | Check linkage |
| Engine runs irregularly or stalls frequently | Defective fuel feed pump | Replace fuel pump |
| Engine runs irregularly or stalls frequently | Improper valve clearance | |
| Engine runs irregularly or stalls frequently | Defective valve spring(s) | |
| Engine runs irregularly or stalls frequently | Poor engine compression | |
| Engine runs irregularly or stalls frequently | Air intake restriction | Check air intake |
| Engine runs irregularly or stalls frequently | Dirty air cleaner | Check and clean air cleaner element |
| Engine runs irregularly or stalls frequently | Stale or bad fuel | Replace fuel |
| Engine runs irregularly or stalls frequently | Improper cooling (Check hoses for blockage and components for function) | Inspect cooling system |
| Engine runs irregularly or stalls frequently | Engine overloaded | Reduce electrical load |
| Engine runs irregularly or stalls frequently | Carbon build-up | Clean carbon from cylinder heads |
| Engine runs irregularly or stalls frequently | Engine malfunction | Troubleshoot engine |
| Stops Suddenly | Out of fuel | Replenish fuel supply |
| Stops Suddenly | Air cleaner clogged | Replace air cleaner element |
| Stops Suddenly | Fuse blown in controller | Replace fuse |
| Stops Suddenly | High engine temperature (HET) shutdown | Check engine coolant level, loose fan belt, radiator obstructions, etc. |
| Stops Suddenly | Low oil pressure (LOP) shutdown | Check engine lube oil level |
| Stops Suddenly | Overcrank shutdown | Add coolant |
| Stops Suddenly | Overspeed shutdown | Replace filter |
| Stops Suddenly | Low Coolant Level (LCL) shutdown | Replace fuse |
| Stops Suddenly | Defective fuel pump | |
| Stops Suddenly | Clogged fuel filter | |
| Stops Suddenly | Defective fuel solenoid | |
| Stops Suddenly | Blown voltage regulator fuse | |
| Stops Suddenly | Remote emergency stop switch activated (if equipped) | Check air intake, oil level, cooling system |
| Stops Suddenly | Engine overheated (hot engine only) | |
| Stops Suddenly | Defective temperature safety shutdown switch | |
| Stops Suddenly | Defective low oil pressure safety shutdown switch | |
| Lacks Power | Air cleaner clogged | Replace air cleaner element |
| Lacks Power | Generator overloaded | Reduce load |
| Lacks Power | Bad or stale fuel | Replace fuel |
| Lacks Power | Engine not running at rated rpm | Check engine speed |
| Lacks Power | Governor defective or misadjusted | Check engine speed |
| Lacks Power | Improper cooling | Check engine coolant level, loose fan belt, radiator obstructions, etc. |
| Lacks Power | Fuel line restriction | Inspect fuel lines |
| Lacks Power | Dirty fuel filter | Replace fuel filter |
| Lacks Power | Improper valve clearance | |
| Lacks Power | Dirty or faulty fuel injectors | |
| Lacks Power | Incorrect fuel injection timing | |
| Lacks Power | Poor engine compression | |
| Lacks Power | Fuel tank vent obstructed | Remove obstruction |
| Engine Overheats | Improper cooling | Check engine coolant level, loose fan belt, radiator obstructions, thermostat, etc. |
| Engine Overheats | Clogged air cleaner | Replace air cleaner element |
| Engine Overheats | Generator set overloaded | Reduce load |
| Engine emits black or gray exhaust smoke | Improper type of fuel | Use proper fuel |
| Engine emits black or gray exhaust smoke | Clogged or dirty air cleaner | Replace air cleaner element |
| Engine emits black or gray exhaust smoke | Defective fuel injection pump | |
| Engine emits black or gray exhaust smoke | Faulty fuel injectors | |
| Engine emits black or gray exhaust smoke | Incorrect fuel injection timing | |
| Engine emits black or gray exhaust smoke | Improper valve clearance | |
| Engine emits black or gray exhaust smoke | Lube oil level too high | Remove surplus lube oil |
| Engine emits black or gray exhaust smoke | Improper grade engine lube oil | Use proper viscosity oil |
| Low lube oil pressure | Low lube oil level | Add engine lube oil |
| Low lube oil pressure | Improper lube oil viscosity | Replace with lube oil of proper viscosity |
| Low lube oil pressure | Defective lube oil pump | |
| Low lube oil pressure | Worn engine components | |
| High lube oil consumption | Too light viscosity oil | Use proper viscosity oil |
| High lube oil consumption | Oil leakage from engine | Check for leakage in lines, around gaskets, drain plug, etc. |
| High lube oil consumption | Clogged breather system | Clean breather system |
| High lube oil consumption | Defective piston ring, cylinder liner, valve guide, valve seat, etc. | |
| High Fuel Consumption | Improper type fuel | Use proper fuel |
| High Fuel Consumption | Clogged or dirty air cleaner element | Replace air cleaner element |
| High Fuel Consumption | Engine overloaded | Reduce load |
| High Fuel Consumption | Improper valve clearance | |
| High Fuel Consumption | Incorrect fuel injection timing | |
| High Fuel Consumption | Poor engine compression | |
| High Fuel Consumption | Fuel leakage | Check for leakage at fuel tank, fuel lines, connections, etc. |
| No battery charging output | Loose or corroded connections | |
| No battery charging output | Sulfated or worn-out battery | |
| No battery charging output | Defective battery charging alternator | Rebuild or replace alternator |
| No battery charging output | Loose alternator belt | Retighten alternator belt |
| No AC output | Circuit breaker open or defective (if equipped) | Reset circuit breaker to ON position Check for voltage on line side |
| No AC output | Circuit breaker tripping due to overload on generator set | Reduce load |
| No AC output | No battery voltage to voltage regulator during cranking + terminals on regulator | Check for DC voltage at voltage regulator terminals |
| No AC output | Blown voltage regulator fuse | Replace fuse; if fuse blows again, check voltage regulator and/or stator winding |
| No AC output | Open wiring, terminal, or pin in build-up circuit or voltage regulator circuit | Check continuity |
| No AC output | Brushes sticking in brush holder or broken brush springs | Check brush position and condition |
| No AC output | Rotor slip rings dirty or corroded | Check slip ring condition |
| No AC output | Defective rotor (open, shorted, or grounded windings) | Check voltage and continuity |
| No AC output | Defective stator (open, grounded, or shorted windings) | Check voltage and continuity |
| No AC output | Defective or misadjusted voltage regulator (PBIIIE only) | Excite rotor separately and check for AC output Readjust voltage regulator |
| No AC output | Defective circuit board K4 relay (field flashing) (relay controller only) | Test/replace relay controller circuit board |
| No AC output | Defective K1 relay (field flashing) (5-Light Controller only) | Test/replace K1 relay |
| Low output or excessive drop in voltage | Engine speed too low | Check engine speed |
| Low output or excessive drop in voltage | Generator overloaded | Reduce load |
| Low output or excessive drop in voltage | Defective voltage regulator | Test/readjust voltage regulator |
| Low output or excessive drop in voltage | Voltage regulator improperly adjusted | Test/readjust voltage regulator |
| Low output or excessive drop in voltage | Defective rotor | Test and/or replace |
| Low output or excessive drop in voltage | Defective stator | Test and/or replace |
| High generator output voltage | Engine speed too high | Check engine speed |
| High generator output voltage | Defective voltage regulator | Test/readjust voltage regulator |
| High generator output voltage | Voltage regulator improperly adjusted | Test/readjust voltage regulator |
| High generator output voltage | Loose voltage regulator connections (including stator sensing leads) | Check voltage regulator connections |
| Overcrank shutdown — generator shuts down; fault shutdown is latched and generator master switch must be moved to off/reset before set can be restarted | Engine does not start after three crank cycles (crank-rest, crank-rest, crank) | |
| Overspeed shutdown — generator shuts down; fault shutdown is latched and generator master switch must be moved to off/reset before set can be restarted | Engine speed exceeds 70 Hz (2100 rpm) on 50/60 Hz sets | |
| Low Oil Pressure (LOP) Shutdown — generator shuts down; fault shutdown is latched and generator master switch must be moved to off/reset before set can be restarted | Engine lube oil pressure falls below 7.1 psi (49 kPa) and LOP switch contacts close | |
| High Engine Temperature (HET) Shutdown — generator shuts down; fault shutdown is latched and generator master switch must be moved to off/reset before set can be restarted | Engine operating temperature reaches 230°F (110°C) and HET switch contacts close | |
| Low Water Level (LWL) Shutdown — generator shuts down; fault shutdown is latched and generator master switch must be moved to off/reset before set can be restarted | Engine coolant level falls below the safe range and LWL sensor decreases circuit resistance | |
| Engine will not crank | Battery not fully charged | Charge battery and attempt restart; if engine will not crank, continue troubleshooting sequence |
| Engine will not crank | Lamps do not light when lamp test button pressed (P3/P4 harness/connections) | Check P3/P4 harness/connections; replace P3/P4 harness |
| Engine will not crank | Controller LED4 not lit | Replace circuit board |
| Engine will not crank | Emergency stop switch activated | Reset emergency stop switch (local and remote) |
| Engine will not crank | Fault shutdown | Correct fault |
| Engine will not crank | Controller LED2 and LED3 not lit with master switch in RUN | Check for DC voltage at fuse F2 (3 amp); if voltage present, replace circuit board; if no voltage, check fuse |
| Engine will not crank | Fuse F2 blown | Replace fuse; if fuse blows again, refer to "Fuses" earlier in this section |
| Engine will not crank | P1 connector/harness, battery connections loose or reversed | Check P1 connector/harness, battery connections |
| Engine will not crank | Engine start circuit defective (P1 harness, starter, solenoid, etc. connections) | Check engine start circuit (P1 harness, starter, solenoid, etc.) connections; repair defective component |
| Engine cranks but will not start | Low fuel | Replenish fuel supply |
| Engine cranks but will not start | LED3 not lit | Check voltage at F3 fuse (15 amp); if voltage present, replace circuit board; if no voltage, inspect fuse |
| Engine cranks but will not start | F3 fuse blown | Replace fuse; if fuse blows again, refer to "Fuses" earlier in this section |
| Engine cranks but will not start | Controller panel lamps not lit | Defective engine starting circuit; check for battery voltage and fuel solenoid |
| Engine cranks but will not start | Circuit board harness/connector pins defective | Repair/replace harness |
| Instrumentation not functioning properly | Loose input or instrument lead connection at AC fuse terminal block (TB3) or instrument | Secure connection |
| Instrumentation not functioning properly | Blown 1.5 amp fuse at AC fuse terminal block (TB3) | Replace fuse |
| Instrumentation not functioning properly | Instrumentation defective | Replace or repair |
| Lamp circuit board not functioning or not functioning properly (fault lamps and alarm horn) | Lamps do not light when lamp test button pressed | Check input voltage at P4-8 and P4-20 soldered connections on lamp circuit board; if no voltage, improper input signal, main circuit board may be defective |
| Lamp circuit board not functioning or not functioning properly (fault lamps and alarm horn) | Lamp circuit board not receiving power | Check ribbon connector between main circuit board and lamp circuit board; if undamaged and properly connected, main circuit board defective, replace |
| Lamp circuit board not functioning or not functioning properly (fault lamps and alarm horn) | Ribbon connector between main circuit board and lamp circuit board damaged or not properly connected | Replace/connect ribbon connector |
| Lamp circuit board not functioning or not functioning properly (fault lamps and alarm horn) | Panel circuit board defective | Replace |
| Engine starts and runs but overcrank lamp flashes | Open speed sensor circuit | Check continuity of wire 2 (black), wire 16 (white), and wire 24 (red) through P1 connector; repair circuit |
| Engine starts and runs but overcrank lamp flashes | Defective speed sensor | See speed sensor test procedures later in this section and in Section 10 |
| Engine starts but shuts down after 30 seconds | Engine safety shutdown (low oil pressure, high engine temperature, overspeed, overcrank, low coolant) | Check oil pressure, water temperature/level; check wiring for overspeed and overcrank conditions |
| Engine starts but shuts down after 30 seconds | Shutdown switches do not function properly | Replace defective switches |
| Engine starts but shuts down after 30 seconds | K3 relay defective | Replace circuit board |
| Engine runs but cannot be stopped by stop switch | Start/stop switch condition/connections defective | Check condition/connections of start/stop switch (local or remote); see component tests following |
| Engine runs but cannot be stopped by stop switch | K2 relay defective | Replace circuit board |
| Engine runs but cannot be stopped by stop switch | Switch defective | Repair/replace switch |
| Engine does not crank (relay controller) | Controller 10 amp fuse blown | Replace fuse |
| Engine does not crank (relay controller) | K2 relay LED not lit | Check condition of controller 10 amp fuse; if fuse O.K., K2 or K4 relay defective, replace circuit board |
| Engine does not crank (relay controller) | K4 relay LED not lit | Verify K4 relay energized by checking for DC (starter solenoid) with start switch in RUN position; if no voltage at K20 relay, K4 relay faulty, replace circuit board |
| Engine does not crank (relay controller) | Start/stop switch condition/connections defective | Check condition/connections of start/stop switch (N, 4, 47); see component tests following |
| Engine does not crank (relay controller) | Battery condition poor | Check battery condition |
| Engine does not crank (relay controller) | Starter and K20 relay defective | Check starter and K20 relay (see component testing and engine service manual) |
| Engine starts but no voltage at fuel pump/fuel solenoid (relay controller) | K1 relay LED not lit | Replace circuit board |
| Engine starts but no voltage at fuel pump/fuel solenoid (relay controller) | Engine wiring harness defective | Check continuity of harness leads; replace harness |
| Engine starts but no voltage at fuel pump/fuel solenoid (relay controller) | Engine fault (fuel pump, fuel solenoid) | Check fuel pump, fuel solenoid |
| No or low AC output | Voltage regulator 10 amp fuse blown | Check condition of voltage regulator 10 amp fuse; replace if blown |
| No or low AC output | Faulty voltage regulator | Separately excite generator; if generator has output, test voltage regulator and wiring |
| No or low AC output | Fault in rotor and/or stator | Separately excite generator; if generator has no output, test rotor and stator |
| Blown F1 fuse (remote annunciator—3 amp) | Defective monitor (if equipped); defective audio-visual alarm (if equipped); defective remote annunciator (if equipped); defective remaining accessories connected to TB1-42A | Isolate defective component and repair or replace |
| Blown F2 fuse (controller—3 amp) | Battery connections reversed; shorted DC supply to indicator panel; shorted controller circuit board | Isolate defective component and repair or replace |
| Blown F3 fuse (engine and accessories—15 amp) | Defective engine electrical components; defective overvoltage board; defective panel lamps, engine gauges | Use ohmmeter to read resistance between designated terminal and ground; isolate defective component and repair or replace |
| Overcrank shutdown fails to function | Speed sensor and related circuitry defective | Check the speed sensor and related circuitry |
| Remote accessories will not operate | Proper voltage not detected at TB1 test point | Test for output voltage at the TB1 terminal strip; check test point connections |
| Blown controller fuse F3 | DEFECTIVE ENGINE ELECTRICAL DEFECTIVE OVERVOLTAGE BOARD DEFECTIVE PANEL LAMPS, ENGINE GAUGES COMPONENTS |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.
Documented causes: Out of fuel; Air cleaner clogged; Defective fuel solenoid; Defective fuel pump. See the table for the matching fixes.
Documented causes: Vent in fuel tank obstructed; Clogged fuel filter; Water, dirt, or air in fuel system; Dirty or faulty fuel injectors. See the table for the matching fixes.
Documented causes: Out of fuel; Air cleaner clogged; Fuse blown in controller; High engine temperature (HET) shutdown. See the table for the matching fixes.