Komatsu Excavator CA555 Fault Code: Crankcase Pressure High Error 1
Also called Crankcase Press High Error 1
Crankcase Pressure High Error 1 · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
CA555 sets when the engine controller (ENG) detects a crankcase pressure high error, level 1. It's logged as an electrical system fault at action level L01, and Komatsu lists no specific controller action or machine symptom tied to it directly. The likely causes point to the KCCV (closed crankcase ventilation) system: a clogged filter, blocked gas piping, or a bad crankcase pressure sensor.
Medium severity. Komatsu classifies this as action level L01 with no specific controller response and no listed machine symptom. That means the machine isn't necessarily derated or shut down by this code alone, but persistent high crankcase pressure can point to blocked ventilation or a sensor problem that deserves a look within the shift rather than being ignored.
What does Komatsu Excavator error code CA555 mean?
CA555 means the engine controller (ENG) has detected that pressure inside the crankcase is reading higher than expected, logged as a level 1 error. This is filed under the electrical system category because it's the sensor circuit and its signal that trip the fault, even though the root issue often lives in the mechanical ventilation path.
The crankcase ventilation system, referred to here as KCCV, is designed to relieve pressure that builds up from combustion gases leaking past the pistons. If that path gets restricted, either at the filter or in the piping, pressure inside the crankcase can climb. A sensor reading that pressure will then report a high value, or a failing sensor itself can generate a false high reading.
Komatsu notes no particular controller action and no specific listed problem on the machine for this code, meaning there's no built-in derate or shutdown described. Still, a genuine high crankcase pressure situation, if left unaddressed, can point to airflow or ventilation issues that are worth chasing down.
Common causes of CA555
- Clogged KCCV filter restricting normal crankcase gas flow
- Blocked KCCV gas piping preventing pressure from venting properly
- Defective crankcase pressure sensor sending a false high reading
How to troubleshoot Komatsu Excavator CA555: first checks
- Use the monitoring function to check signal voltage from the crankcase pressure sensor (monitor code 48401 (V))
- Use the monitoring function to check the actual pressure value from the crankcase pressure sensor (monitor code 48400 (MPa))
- Inspect the KCCV filter for clogging or heavy buildup and replace if dirty
- Trace and inspect the KCCV gas piping for blockage, kinks, or collapsed sections
- Check the crankcase pressure sensor's wiring and connector for corrosion or damage before condemning the sensor
- Turn the starting switch to the ON position to attempt to reproduce the failure code, as listed in the reproduction method
How the code clears
No separate clearing step is listed. Komatsu's documented method to reproduce the code is simply turning the starting switch to the ON position, which suggests the fault is checked and can be observed as soon as the key is cycled. Address the underlying cause (filter, piping, or sensor) and then verify with the monitoring function that pressure and signal voltage read normally before considering the code resolved.
Frequently asked questions
What does CA555 mean on a Komatsu excavator?
It means the engine controller detected a crankcase pressure high error at level 1. It's logged under the electrical system category since the sensor and its signal are what actually trip the code.
Will CA555 shut down or derate my Komatsu excavator?
Komatsu lists no particular controller action and no specific machine symptom for this code, so there's no documented automatic shutdown or derate tied to CA555 itself.
What usually causes a crankcase pressure high error?
Komatsu lists three possible causes: a clogged KCCV filter, blocked KCCV gas piping, or a defective crankcase pressure sensor.
How do I check the crankcase pressure sensor on a Komatsu?
You can check the sensor's signal voltage using monitor code 48401 (V) and the pressure reading itself using monitor code 48400 (MPa) through the monitoring function.
How do I reproduce or confirm CA555 for diagnosis?
Komatsu's listed method is simply turning the starting switch to the ON position.
Is CA555 an electrical fault or an engine mechanical fault?
Komatsu files it under the electrical system category since it's a sensor circuit fault, but the root cause is often mechanical, tied to restricted crankcase ventilation from a clogged filter or blocked piping.