Cylinder 1 Injector Circuit Open or Shorted
The KOHLER-COMMAND-P0201 (Kohler Command EFI) diesel fault code means: Cylinder 1 Injector Circuit Open or Shorted. This is a serious severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- moderate
- Estimated cost
- $40-$120 DIY for injector replacement or harness repair. Pro diagnosis and repair typically $150-$400 depending on whether the ECM is involved.
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Common Symptoms
- Engine cranks but runs rough or misfires noticeably at idle and under load
- Hard start or extended cranking before engine fires
- EFI fault light or LED blink code active on dash or engine control panel
- Engine bogs down under mowing load and may surge or stumble
- Visible black or unburned fuel smoke from exhaust during operation
- Engine may start and run on one cylinder only, with noticeably reduced power
- Kohler PCM diagnostic tool or equipment manufacturer dash displays P0201 stored or active
Probable Causes (Ranked by Likelihood)
- Failed or electrically open fuel injector on cylinder 1, causing no fuel delivery to that cylinder Very Likely
- Broken, corroded, or disconnected wiring harness connector at the cylinder 1 injector plug Very Likely
- Chafed or shorted injector wiring harness, often from heat or routing contact with exhaust components Likely
- ECM output driver failure for injector 1 circuit, preventing proper injector pulse Possible
- High injector coil resistance caused by internal injector degradation or carbon contamination Possible
- Corroded ECM harness connector pins at the injector driver terminal Less Likely
- Fuel system pressure loss causing injector to behave erratically, mistaken for circuit fault Less Likely
Step-by-Step Diagnostic Procedure
Connect the Kohler PCM diagnostic tool if available and confirm P0201 is active or pending. Note whether additional codes like P0300 or P0301 are stored alongside it, which would confirm a cylinder 1 misfire.
Locate the cylinder 1 injector connector on the engine. On ECV twin-cylinder engines, cylinder 1 is typically the flywheel-side cylinder. Unplug the connector and inspect it for bent pins, corrosion, moisture, or melted plastic from heat.
With the injector unplugged and ignition key in the RUN position but engine not cranking, use a multimeter set to DC volts and probe the harness side of the connector. You should see battery voltage (around 12V DC) on one terminal when the key is on. No voltage here points to a wiring or ECM supply problem.
Measure injector coil resistance with the injector unplugged and the engine off. Set your multimeter to ohms and probe both injector terminals directly. Kohler EFI injectors typically measure between 12 and 16 ohms. A reading below 5 ohms indicates a shorted coil. An open-loop (OL) reading indicates a failed open coil. Either condition requires injector replacement.
Inspect the full length of the wiring harness from the injector connector back toward the ECM. Look for chafing against the valve cover, routing too close to the exhaust manifold or muffler, zip tie damage, or any visible bare wire. Repair any damaged sections with heat-rated automotive wiring repair connectors.
If wiring and injector resistance check out, swap the cylinder 1 and cylinder 2 injectors and clear the code. If the fault follows the injector to the cylinder 2 position (code changes to P0202), the injector itself is bad. If the fault stays on P0201, the problem is in the wiring or ECM driver circuit for cylinder 1.
If all wiring and injector tests pass and the code persists, the ECM output driver for injector 1 may be damaged. This requires the Kohler PCM diagnostic tool and likely ECM replacement. Contact a Kohler-authorized outdoor power equipment dealer for that step.
Frequently Asked Questions
What does Kohler code P0201 mean on my commercial mower?
P0201 means the ECM detected a problem in the electrical circuit controlling the fuel injector on cylinder 1. It could be a failed injector, a broken wire, a corroded connector, or in rare cases a problem inside the ECM itself. The engine may still run, but it will likely misfire, lose power, and run rough because that cylinder is not getting proper fuel delivery.
Can I still mow with P0201 active?
You can run the mower in a limited way, but you should not rely on it for a full day of commercial work. A misfiring cylinder puts extra load on the engine, runs hotter, and can cause downstream damage. Get it diagnosed before your next full shift.
How much does it cost to fix P0201 on a Kohler EFI engine?
If it is just a bad injector, expect to spend $40 to $80 on a replacement injector and handle it yourself with basic tools. If you need a shop, labor plus parts typically runs $150 to $300. If the ECM driver is damaged, costs can reach $350 to $500 or more at a dealer.
Will my mower start next time with this code stored?
Most likely yes, it will still crank and start, but it will run rough on one cylinder. The code does not lock the ECM out from starting. However, if the injector circuit is completely open, that cylinder contributes no power and the engine condition will be noticeably poor from the first second of start-up.