Applicable Systems
EMCP 4.2
Symptoms
Monitor display flickers and occasionally goes blank. No other machine faults.
Possible Causes
- Loose CAN bus connector behind monitor.
- Monitor backlight inverter failing.
- Corroded ground connection at cab harness junction.
Troubleshooting Steps
- Step 1: Wiggle monitor harness connectors and observe display.
Flickering stops when connector fully seated with click. - Step 2: Measure monitor supply voltage at pin A1 (key-on).
Voltage steady 24–28 VDC; no drop during flicker. - Step 3: Check ground point G102 in cab behind right panel for corrosion.
Ground resistance < 0.5 Ω to frame; no green corrosion visible.
How to Reset
Reseat monitor connectors, apply dielectric grease; replace monitor if backlight inverter failed.
Common Replacement Parts
- Monitor Assembly 227-7698: Monitor Assembly 227-7698
- Dielectric Grease 4C-4767: Dielectric Grease 4C-4767
Frequently Asked Questions
- Q: Can I use a generic 24V monitor?
No, Cat monitors contain machine-specific calibration data.
- Q: What CAN bus speed does 320 use?
250 kbps for implement CAN; 500 kbps for powertrain CAN.
Source: Caterpillar 320 Excavator Electrical Schematic Manual
Category: Heavy Equipment