What CA428 Actually Means
CA428 is specific to the PC210-8, and it relates to the electronic displacement control on the pump's proportional solenoid valve. The machine's ECM (engine control module) monitors the electrical signal going to this solenoid, which is what allows the pump's displacement — and therefore its output — to be electronically adjusted rather than purely mechanically regulated. When the ECM detects abnormal voltage in that circuit, it raises CA428.
The critical thing to understand: this fault code is about the control circuit, not necessarily the pump's mechanical internals. Abnormal voltage in a solenoid circuit has a few genuinely different possible causes, and only one of them requires opening up the pump itself.
Three Things That Can Trigger CA428
- A worn or damaged solenoid valve — this genuinely is a pump-internal issue, and does typically mean the pump needs attention.
- Corroded or chafed wiring near the pump mounting bracket — this is documented as a known weak point on this model specifically. The harness routing near the mounting bracket is exposed to vibration and, on machines that work in wet or muddy conditions, moisture ingress at the connector.
- Contaminated hydraulic oil affecting solenoid response — less common, but contamination inside the valve body can produce erratic electrical readings even when the physical wiring is intact.
What to Check Before You Order a Pump
Given that cause #2 above is a documented, known issue on this specific model, it's worth ruling out before assuming the worst:
- Inspect the wiring harness specifically where it routes near the pump mounting bracket for visible chafing, cracked insulation, or corrosion at the connector pins.
- Check that the connector is fully seated and hasn't worked loose from vibration.
- If accessible, look for green/white corrosion buildup at the connector — a common sign of moisture ingress in outdoor equipment.
If the harness and connector check out clean and the fault persists, the issue is more likely internal to the pump or solenoid — at that point, sourcing a correctly tested replacement is the sensible path.
A Related Symptom to Watch For
CA428 often shows up alongside erratic pressure — surging or unexpectedly dropping. This is consistent with the ECM entering a failsafe mode that limits pump output to protect the system once it detects the abnormal solenoid signal. If you're seeing both symptoms together, that's additional confirmation this is genuinely the CA428-related circuit, not an unrelated pressure issue.
If You Do Need a Replacement
The PC210-8 runs a Komatsu HPV95 pump — the same base architecture used across the PC200/PC210 class, and notably, the same pump fitted to the Komatsu D65EX bulldozer. We cover the full specification, genuine part number references, and our testing process on our dedicated PC210-8 pump page.