Coolant Temp Sensor Circuit High Voltage Fault
The KIOTI-P0118 (Daedong) diesel fault code means: Coolant Temp Sensor Circuit High Voltage Fault. This is a moderate severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- moderate
- Estimated cost
- DIY sensor replacement $25-$60 for the sensor plus your time. Professional diagnosis and repair at a Kioti dealer $80-$200 depending on labor rate and whether the fault is the sensor alone or requires harness repair.
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Common Symptoms
- Instrument cluster shows P0118 or a coolant temperature warning light stays on
- Coolant temperature gauge reads unusually high or pegs at maximum even on a cold start
- Engine takes longer than normal to reach operating temperature or fan runs constantly
- ECM applies a fixed default coolant value, so cold-start fueling and glow plug timing may feel off
- DPF regen cycles may trigger more often or behave erratically because ECM loses real temperature feedback
- Engine may run rough at idle during warmup due to incorrect fueling correction
- In some cases the tractor enters a reduced-power derate to protect against a perceived overheat condition
Probable Causes (Ranked by Likelihood)
- Open circuit in the coolant temperature sensor wiring harness (broken wire or corroded connector pin) Very Likely
- Failed engine coolant temperature sensor sending full supply voltage back to ECM instead of a resistance-scaled signal Very Likely
- Corroded or backed-out connector at the coolant temperature sensor plug near the engine block or head Likely
- Damaged wiring where the harness runs close to the exhaust or DPF, causing insulation melt and an open wire Likely
- Internal ECM input circuit fault causing it to read the sensor line as open Possible
- Coolant temperature sensor contaminated or coated with deposits, shifting its resistance out of range Less Likely
Step-by-Step Diagnostic Procedure
Step 1 -- Safety first. Park the tractor on level ground, set the parking brake, turn the key OFF, and let the engine cool completely before touching any sensors or wiring.
Step 2 -- Locate the engine coolant temperature sensor. On most Daedong 3- and 4-cylinder engines it threads into the coolant passage on the cylinder head or upper engine block, near the thermostat housing. It has a single 2-wire connector.
Step 3 -- Inspect the connector and wiring. Unplug the sensor connector and look for bent pins, green corrosion, pushed-back terminals, or cracked insulation. Wiggle the harness back toward the firewall and look for spots where it may have rubbed through or melted against the exhaust or DPF.
Step 4 -- Measure sensor resistance. With the connector unplugged and the engine cold (ambient temperature), set your multimeter to resistance (ohms). Probe across the two sensor terminals. A good Daedong coolant temperature sensor reads roughly 2,000 to 3,000 ohms at 20 degrees C (68 F). A reading of OL (open loop / infinite resistance) confirms the sensor has failed internally.
Step 5 -- Check the reference voltage from the ECM. Reconnect the sensor, then carefully back-probe the harness connector (or use a T-pin in the back of the connector). With the key in the RUN position but engine off, you should see approximately 5 volts DC on the signal wire. If you see the full 5 volts with the sensor connected, the ECM is seeing an open circuit, which confirms either the sensor or the wiring is broken.
Step 6 -- Do a continuity check on the harness. Unplug the sensor and unplug the ECM harness connector (note: on Tier 4 Final models this step requires care -- if you are not comfortable accessing the ECM connector, stop here and call your Kioti dealer). With both ends unplugged, use your multimeter on continuity mode and check each wire between the sensor connector and the ECM. No beep means an open wire in that run.
Step 7 -- If the sensor tests bad (open), replace it with a genuine Daedong coolant temperature sensor for your engine code. Coat the threads lightly with thread sealant, torque to spec (typically 15 to 20 Nm), reconnect the harness, and clear the DTC with the instrument cluster code-clear procedure or a Kioti dealer scan tool over CAN.
Step 8 -- After repair, start the engine and watch the coolant temperature gauge rise steadily from cold to the normal operating range (roughly the middle of the gauge). If P0118 returns immediately, the fault is in the wiring or the ECM input, and you will need a Kioti dealer scan tool for further diagnosis.
Frequently Asked Questions
What does Kioti code P0118 mean on my tractor?
P0118 means the ECM is reading an abnormally high voltage on the coolant temperature sensor signal wire, which usually means the circuit is open. That open circuit could be a broken wire, a corroded connector, or a failed sensor. Because the ECM can not read actual coolant temperature, it substitutes a fixed default value and logs this code.
Can I still drive or use my tractor with P0118 active?
You can operate it for short periods, but do so carefully. The ECM is running on a substitute coolant temperature value, which means cold-start fueling and DPF regen decisions are based on a guess, not real data. There is also a risk you would not get a reliable overheat warning if the cooling system actually started to fail. Fix it before any extended or heavy work.
How much does it cost to fix P0118 on a Kioti tractor?
If the coolant temperature sensor itself is bad, it is a relatively low-cost repair. The sensor part is typically $25 to $60, and most owners with basic tools can replace it in under an hour. If the fault is a broken wire or corroded harness, add some time and material for repair. A dealer visit for diagnosis plus sensor replacement typically runs $80 to $200.
Will P0118 cause my Kioti to overheat or damage the engine?
The code itself does not cause overheating. The risk is that with a failed coolant temperature sensor, the ECM may not alert you properly if the engine actually does overheat for another reason, like a coolant leak or a stuck thermostat. Address the code promptly so you have reliable temperature monitoring, especially if you are running the tractor hard or in warm weather.
P0118 on Other Platforms
The same code ID appears across other engines, vehicles, and equipment. Diagnostic flow varies by platform — see the matching breakdown: