Low Coolant Level Shutdown Triggered
The PERKINS-111-1 (Kohler RDC2) diesel fault code means: Low Coolant Level Shutdown Triggered. This is a critical severity code.
- Keep driving?
- No -- stop driving
- DIY difficulty
- moderate
- Estimated cost
- Coolant top-off and sensor replacement DIY: $20-$80. Professional diagnosis and coolant system repair: $150-$600. Head gasket repair if internally leaked: $1,200-$3,500 depending on engine size.
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Common Symptoms
- Generator shuts down and displays fault code 111-1 on the PowerWizard 1.1 or 2.0 panel
- Red shutdown lamp illuminates on the control panel
- Generator cranks but will not stay running, or stops within seconds of reaching run speed
- Audible alarm sounds continuously after shutdown
- READY light goes out and the unit will not accept a remote start command
- Coolant overflow reservoir appears empty or radiator cap area shows dried coolant residue
- Engine may feel unusually hot to the touch near the block or hoses after the fault occurs
Probable Causes (Ranked by Likelihood)
- Coolant lost through an external leak at a hose, hose clamp, or radiator fitting Very Likely
- Low coolant level switch or float sensor has failed in the open position, sending a false low-level signal Likely
- Coolant lost internally through a blown head gasket, allowing coolant to burn off or enter the oil Possible
- Coolant reservoir ran dry due to normal evaporation and system was never topped off during routine maintenance Possible
- Wiring harness to the coolant level sensor has a broken wire or corroded connector causing an open circuit Possible
- Radiator pressure cap is faulty, not holding system pressure and allowing coolant to push out under load Less Likely
- Coolant pump seal leaking internally, reducing effective coolant volume without visible external puddle Less Likely
Step-by-Step Diagnostic Procedure
Before you touch anything, let the engine cool for at least 30 minutes. NEVER open the radiator cap on a hot engine. Pressurized coolant can cause serious burns.
Once cool, visually inspect the ground under the generator and all around the base. A puddle of green, orange, or pink fluid is a strong sign of an external leak. Trace hoses, clamps, and the radiator face for wet spots or dried residue.
Check the coolant overflow reservoir (the translucent plastic tank near the radiator). The level should sit between the MIN and MAX marks. If it is empty or below MIN, the system is genuinely low and needs topping off with the correct 50/50 premix coolant before you do anything else.
With the engine cold, carefully remove the radiator cap and look at the coolant level inside the filler neck. It should be full to the base of the neck. If it is low, add coolant and note how much you added. A large deficit with no visible external leak points to an internal issue.
Locate the coolant level sensor, typically a float switch mounted on the top tank of the radiator or on the coolant header. Unplug the connector and inspect the pins for green corrosion or pushed-back terminals. Use a multimeter set to continuity mode. With the sensor disconnected and the coolant full, the switch should show continuity (closed circuit). If it shows open with a full system, the sensor has likely failed.
Check the engine oil dipstick and look at the oil on the stick. If the oil looks milky, frothy, or is above the full mark with no known oil addition, coolant is leaking into the engine internally. Stop here and call a qualified technician. Do not run the engine.
After refilling coolant and inspecting the sensor, reset the fault on the PowerWizard controller by pressing the STOP button, then cycling to AUTO. If the fault returns immediately with a confirmed full coolant level, suspect the sensor or wiring. If the fault returns after a run cycle, suspect an active leak under load.
If you cannot identify the leak source or the fault keeps returning, connect Perkins EST (Electronic Service Tool) to the ECM diagnostic port. EST will show real-time sensor voltage for the coolant level circuit and log when the fault first activated. This step requires a licensed technician with the EST software.
Frequently Asked Questions
What does Perkins code 111-1 mean?
Code 111-1 means the coolant level sensor detected that the engine coolant has dropped below the safe minimum level. The controller treats this as an emergency and shuts the engine down to prevent overheating and serious internal engine damage. The number 111 is the Perkins parameter identifier for coolant level, and the -1 suffix means the value went below the allowed lower limit.
Can my generator still run with this code?
No. Code 111-1 is a hard shutdown fault. The PowerWizard controller will not allow the engine to keep running or restart until the fault is cleared. If a power outage happens while this code is active, the generator will attempt to crank but will shut down again almost immediately if the underlying problem is not fixed first.
How much does it cost to fix?
If the fix is simply topping off coolant and tightening a loose hose clamp, you might spend $20 to $80 in coolant on your own. Replacing a faulty coolant level sensor is a $50 to $150 part and a moderate DIY job. If there is a serious leak, a blown head gasket, or a failed water pump, expect a professional repair bill of $600 to $3,500 or more depending on the engine size and what parts are needed.
Will the generator start the next time the power goes out?
Not reliably. The 111-1 fault locks out the unit until it is cleared. Even if you manually reset it and it starts briefly, a genuine low coolant condition will trigger the shutdown again within seconds of reaching operating RPM. You need to fix the root cause and clear the fault properly before the generator will respond to an automatic transfer command from the ATS.