Glow Plug Circuit Fault Detected at Startup
The KUBOTAGEN-E07 (Cummins Onan) diesel fault code means: Glow Plug Circuit Fault Detected at Startup. This is a moderate severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- moderate
- Estimated cost
- $30-$120 DIY (glow plugs $8-$25 each, relay $15-$40). Pro repair including labor typically $150-$400 depending on how many plugs need replacement and harness repair work.
A $30 car code reader can't do diesel. The HD7000 reads full-system codes and does parked DPF regen, idle/speed-limit, and service resets from the cab — on everything from a 6.7 Cummins/Power Stroke/Duramax pickup to Class-8 trucks (Detroit, Paccar, CAT, Volvo, Mack, International).
Check Price on AmazonAffiliate link -- we earn a commission at no extra cost to you.
Full-system 6/9/16-pin diesel scan tool for Cummins, Paccar, CAT, Detroit and more — plug-and-play, no subscription. A cheaper way to read heavy-duty codes a basic OBD2 scanner skips entirely.
Check Price on AmazonAffiliate link -- we earn a commission at no extra cost to you.
Common Symptoms
- Panel displays E:07 during or immediately after the preheat cycle
- Generator cranks but struggles to fire in cold weather
- White or gray smoke during attempted cold start
- Genset starts fine when ambient temperature is above 60 degrees F but fails below 40 degrees F
- Preheat indicator light does not illuminate or goes out faster than normal
- Generator eventually starts after several crank attempts in mild weather but trips on E:07
- READY light never appears after turning the panel switch to AUTO in cold conditions
Probable Causes (Ranked by Likelihood)
- One or more glow plugs burned out or open-circuit, causing the controller self-test to fail Very Likely
- Glow plug relay failed or has burned contacts, preventing voltage from reaching the glow plug circuit Very Likely
- Broken or corroded wiring harness connector at the glow plug relay or individual glow plug terminals Likely
- Glow plug controller or timer module fault causing the preheat cycle to terminate too early Possible
- Low battery voltage causing insufficient current to complete the high-draw glow plug preheat cycle Possible
- Blown fuse on the glow plug relay circuit Less Likely
- ECU or genset controller internal fault misreading a healthy glow plug circuit as failed Less Likely
Step-by-Step Diagnostic Procedure
Check battery voltage first. Set your multimeter to DC volts and measure across the battery terminals. You need at least 12.4 V at rest and 11.5 V or higher during cranking. A weak battery drops voltage during the preheat cycle and can trigger E:07 even with good glow plugs.
Locate the glow plug relay. On most Kubota genset packages it is a black cube relay mounted on or near the valve cover or firewall. With the panel in OFF, use your multimeter set to DC volts. Turn the key or panel switch to preheat and confirm the relay coil terminals see battery voltage (12 V DC) during the preheat window. If not, trace the wire back to the controller fuse block.
Check the fuse protecting the glow plug relay circuit. Refer to your genset wiring diagram or Kubota Diagmaster diagnostic software for the fuse location. Replace any blown fuse with the exact amperage rating printed on the fuse holder.
Test each glow plug individually. Remove the glow plug wire or bus bar. Set your multimeter to resistance (ohms). A healthy Kubota glow plug reads 0.5 to 2 ohms between the terminal and the plug body. A reading of OL (open loop) or more than 5 ohms means that plug is failed and needs replacement.
Inspect the glow plug terminals and wiring. Look for white powder (corrosion), melted insulation, or terminals that pull off with light finger pressure. Corroded terminals cause a resistance spike that the controller reads as a circuit fault. Clean terminals with electrical contact cleaner and a wire brush, then recheck resistance.
With all plugs confirmed good, test the relay output. During preheat, backprobe the relay output terminal with your multimeter set to DC volts. You should see battery voltage at the glow plug bus bar for the full preheat window (typically 6 to 20 seconds depending on coolant temperature). No voltage here with a good coil signal means the relay contacts are burned. Replace the relay.
If all hardware tests pass, connect a laptop running Kubota Diagmaster diagnostic software to read live controller data. Diagmaster will show the preheat cycle timer value and whether the ECU is seeing a current draw from the glow plug circuit. This step requires the Kubota Diagmaster software and the correct USB diagnostic harness. If you do not have this equipment, contact a Kubota-certified genset technician.
Common Fixes by Vehicle
What techs usually find when diagnosing KUBOTAGEN-E07 on specific platforms — tap a platform for the fix and the exact part:
Kubota D902 / D1105 / V1505 powered gensets Easy DIY
Kubota E:07 (Glow Plug Circuit Fault) is a hard-start blocker on cold mornings. Test each glow plug with a multimeter -- spec is 0.5-1.5 ohms cold. Plugs that read open or above 5 ohms are bad; replace as a set ($15-$25 each, 3-4 plugs depending on engine). Also check the glow plug relay near the battery -- contacts burn out on these. The relay is $25-$50 and is a 15-minute swap.
Labor: 30-60 minFrequently Asked Questions
What does Kubota genset code E07 mean?
E:07 means the genset controller ran its preheat self-test and detected a problem in the glow plug circuit. Glow plugs are small electric heaters inside each cylinder that warm the combustion chamber before a cold diesel start. When one or more plugs fail, or when the relay that powers them fails, the engine has trouble firing in cold weather. The controller logs E:07 and alerts you so you can fix it before a cold night leaves you without power.
Can my generator still run with this code?
It depends on the temperature. In warm weather above 60 degrees F, the engine may start and run normally because glow plugs are less critical when the air is already warm. Below 40 degrees F you will likely see hard starts, white smoke, or a complete no-start. Do not ignore this code going into fall or winter. The genset will become unreliable exactly when you need it most.
How much does it cost to fix?
If you are comfortable with basic hand tools and a multimeter, budget $30 to $120 for parts. Individual glow plugs run $8 to $25 each and Kubota engines typically have 2 to 4 cylinders, so replacing all plugs at once costs $25 to $100. A replacement relay is $15 to $40. If you hire a technician, expect $150 to $400 total including diagnostic time and labor, more if the wiring harness needs repair.
Will the generator start the next time the power goes out?
In warm weather it probably will. In cold weather, E:07 is a real risk to emergency reliability. The genset may crank without firing, leaving you without power during an outage. Fix this code before cold weather arrives. At minimum, test the plugs and relay now so you know exactly what is failed and what parts to order.
E07 on Other Platforms
The same code ID appears across other engines, vehicles, and equipment. Diagnostic flow varies by platform — see the matching breakdown: