Charging System Low Voltage During Run
What does KUBOTAGEN-E06 mean?
The KUBOTAGEN-E06 (Cummins Onan) diesel fault code means: Charging System Low Voltage During Run. This is a moderate severity code.
Common Symptoms
- Panel displays E:06 while the genset is running or immediately after shutdown
- Battery warning light or alarm LED illuminates on the control panel
- Genset cranks slowly or fails to start on the next attempt after a long run
- Battery voltage reads below 13.0 V DC while the engine is running at normal speed
- Genset starts fine but shuts itself down after extended run time with no other fault
- Visible corrosion or loose connection at the battery terminals or charging harness
- Multimeter test at battery posts shows little or no rise in voltage when engine is running
Probable Causes (Ranked by Likelihood)
- Worn or failed battery charging alternator (excitation coil or rectifier bridge faulty, not producing adequate DC output) Very Likely
- Loose, broken, or corroded wiring between the alternator charge output and the battery terminals Very Likely
- Battery has reached end of service life and will not hold or accept a charge even when alternator output is normal Likely
- Alternator drive belt slipping, glazed, or broken, preventing the charging alternator from spinning at full speed Likely
- Faulty internal voltage regulator inside the alternator, causing intermittent or low charge output Possible
- Corroded or high-resistance battery ground connection to the genset frame preventing proper charge circuit completion Possible
- Controller sensing circuit fault or wiring issue causing a false E06 reading when actual alternator output is normal Less Likely
Step-by-Step Diagnostic Procedure
Start with a baseline battery check. With the genset OFF, set your multimeter to DC volts and probe the battery terminals. A healthy 12 V battery should read 12.4 V or higher. Below 12.0 V means the battery is already discharged and needs to be addressed first.
Start the genset and let it warm up for two to three minutes, then measure battery voltage again at the battery terminals. You should see 13.6 V to 14.4 V DC. A reading below 13.0 V confirms the charging system is not delivering enough output while the engine runs.
Inspect the alternator drive belt. Locate the small charging alternator mounted on the engine (separate from the main AC generator head). Check the belt for cracks, glazing, fraying, or excessive slack. Press the belt with your thumb midway between pulleys. It should deflect no more than about 10 mm. Replace the belt if it is visibly worn or slipping.
Check every wiring connection in the charging circuit. Trace the wires from the alternator output terminal to the battery positive post, and the ground wire from the battery negative to the engine block or genset frame. Look for corrosion, loose connectors, cracked insulation, or terminals that pull off with light hand pressure. Clean corroded terminals with a wire brush and dielectric grease.
With the engine running, use your multimeter to measure DC voltage directly at the alternator output terminal (the B+ stud on the alternator) versus the alternator case ground. If you read 13.6 V or higher here but still low at the battery, the problem is in the wiring between the alternator and battery. If voltage is low at the alternator output terminal itself, the alternator or its internal regulator has failed.
Load-test the battery. If you have access to a battery load tester (available at most auto parts stores for free loan), test the battery under load. A battery that collapses below 9.6 V under a 15-second load test needs replacement regardless of what the charging system does.
If all wiring and belt checks pass but alternator output is still below 13.6 V at the alternator terminals, the alternator assembly requires bench testing or replacement. This step requires either a charging system tester or a replacement alternator to swap in. Contact a Kubota dealer or genset service technician at this point.
After any repair, clear the E06 code by cycling the control panel power OFF and back to AUTO or RUN. Run the genset for 10 minutes and recheck battery voltage to confirm the fault is resolved.
Frequently Asked Questions
What does Kubota genset code E06 mean?
E06 means the controller detected that the charging alternator is not keeping the battery charged while the engine runs. The battery voltage dropped below the expected threshold during operation. The genset may continue running for now, but the battery is slowly draining, and if nothing is fixed, the next start attempt may fail because there is not enough battery power to crank the engine.
Can my generator still run with the E06 code?
Yes, in most cases the genset will continue to produce AC power during the current run cycle. However, reliability is reduced. The longer it runs without a functioning charging circuit, the more the battery drains. If power is restored and the genset shuts down normally, it may not crank again when the next outage occurs. Treat this as an urgent issue, not something to ignore.
How much does it cost to fix E06?
It depends on the root cause. A new drive belt is $15-$35 and is an easy DIY fix. A replacement battery runs $60-$120 and is also straightforward. If the charging alternator itself has failed, parts run $80-$220, and a shop will add $80-$150 in labor. Most E06 repairs land in the $50-$250 range total, with wiring issues on the low end and alternator replacement on the high end.
Will the generator start the next time the power goes out?
That depends on how far the battery has discharged and how quickly you address the fault. If the battery is still above 12.0 V and the outage happens soon, the genset will likely crank. If the battery has been slowly draining through repeated run cycles without a working charger, the next start could fail completely. Do not leave E06 unresolved if you depend on the genset for emergency backup power.
E06 on Other Platforms
The same code ID appears across other engines, vehicles, and equipment. Diagnostic flow varies by platform — see the matching breakdown: