Emergency Stop Input Open or E-Stop Activated
What does KOHLER-20 mean?
The KOHLER-20 (Kohler RDC2) diesel fault code means: Emergency Stop Input Open or E-Stop Activated. This is a serious severity code.
Common Symptoms
- Generator displays fault code 20 on the RDC2 controller display panel
- Generator shuts down immediately and will not restart
- Red fault light is illuminated on the controller panel
- AUTO mode does not allow the generator to crank even during a power outage
- Alarm horn sounds at shutdown and does not clear on its own
- Generator completes a normal exercise start but trips on code 20 before producing power
- Fault persists after pressing the OFF button and attempting to reset
Probable Causes (Ranked by Likelihood)
- Remote e-stop button is physically pressed or latched in the activated position Very Likely
- E-stop input wiring loop is open due to a broken, disconnected, or corroded wire between the controller and the remote e-stop terminal Very Likely
- Remote e-stop switch contacts have failed open internally, breaking the safety loop even though the button appears released Likely
- Terminating jumper or shorting plug missing from the e-stop terminal block on the RDC2 controller when no remote switch is installed Likely
- Water or rodent damage to the e-stop wiring harness causing an intermittent open circuit Possible
- ATS or external control panel wired in series with the e-stop loop has an open internal contact Possible
- RDC2 controller input board fault causing a false open reading on the e-stop input terminal Less Likely
Step-by-Step Diagnostic Procedure
Start at the remote e-stop button, usually a red mushroom-head button mounted near the generator or on a wall panel. Twist and pull it clockwise to release a latched e-stop. If no remote button is installed, move to the next step.
Locate the RDC2 controller terminal block inside the generator control panel. Find the terminals labeled ESTOP or E-STOP (check your Kohler wiring diagram for your model). With the generator in OFF, look for a small shorting jumper or two wires looped between those terminals. Confirm the loop is present and tight.
If a remote e-stop switch is wired in, disconnect it at the generator terminal block and install a temporary shorting jumper (a short piece of wire) across the two ESTOP terminals. Attempt to clear the fault by pressing OFF and then switching to AUTO. If the fault clears, the problem is in the remote switch or its wiring.
Inspect all wiring between the controller ESTOP terminals and the remote switch. Look for cut, pinched, or corroded wires, and check each connector for loose pins. Repair or replace any damaged wire and retest.
Use a multimeter set to resistance (Ohms). With the generator OFF and the e-stop button released, measure resistance across the two ESTOP input terminals at the controller. A healthy closed loop reads near 0 Ohms. A reading of OL or infinity confirms an open circuit somewhere in the loop.
If the loop measures closed at the controller but the fault still appears, measure DC voltage on the ESTOP input terminal with the generator powered. Compare to the Kohler spec for your model (typically 12 VDC present on a healthy closed input). A voltage reading outside spec points to a controller input board issue -- call a certified Kohler technician at this point.
After restoring the e-stop loop, press OFF to clear the fault, wait 10 seconds, then switch to AUTO. Confirm the fault code 20 no longer appears and the generator returns to READY status on the RDC2 display panel.
If the fault returns intermittently, suspect a failing e-stop switch with marginal contacts. Replace the switch even if it appears to reset correctly, because an intermittent open will cause nuisance shutdowns during a real outage.
Frequently Asked Questions
What does Kohler code 20 mean on my generator?
Code 20 means the RDC2 controller detected that the emergency stop input loop is open. This happens when someone presses a remote e-stop button, when the wiring connecting that button to the controller is broken or disconnected, or when a required shorting jumper is missing from the e-stop terminals. The controller treats any open in that loop as an intentional emergency stop and refuses to run the generator until the circuit is restored.
Can my generator still run with code 20 active?
No. Code 20 is a hard shutdown. The generator will not crank or produce power in any mode, including AUTO, while this fault is active. You must find and fix the open e-stop circuit, then clear the fault before the generator will operate again.
How much does it cost to fix Kohler code 20?
If the fix is as simple as releasing a latched e-stop button or installing a shorting jumper, it costs nothing. Replacing a failed e-stop switch runs $15 to $80 in parts and is a moderate DIY task. If a wiring harness needs replacement or the RDC2 controller board itself is faulty, a professional technician will typically charge $150 to $400 for diagnosis and repair.
Will my generator start the next time the power goes out with code 20 showing?
No. While code 20 is active, the generator will not respond to a utility power failure. It will stay off even in AUTO mode. Fix the e-stop loop and clear the fault before the next storm or outage, or you will be without backup power when you need it most.