International MID 128 PID 111 FMI 4: Meaning, Causes & Fix
Coolant Level Sensor — signal voltage below normal or shorted low
Diagnostic Reference
| Field | Details |
|---|---|
| Code | MID 128 PID 111 FMI 4 |
| Protocol | J1587 MID: 128 PID: 111 |
| Component | Engine Coolant Level Sensor |
| Manufacturer | International |
| Engine Series | A26 |
| Severity | 🟠 CHECK SOON |
| SAE Reference | SAE J1587/J1708 — MID 128, PID 111 |
Possible Causes
- Sensor float stuck in low position from sludge
- Sensor connector corroded
- Sensor 5V reference wire shorted to ground
- Coolant residue on sensor probe giving false low reading
Diagnostic & Repair Procedure
- Step 1: Clean coolant level sensor probe with Scotch-Brite pad
- Step 2: Check for 5V reference at sensor connector with key on
- Step 3: Measure sensor output voltage
- Step 4: Flush cooling system if sludge present on sensor
- Step 5: Replace sensor if float is mechanically stuck
Frequently Asked Questions
Is this a false alarm or a real problem?
CHECK SOON codes are rarely false alarms. The ECM has detected a parameter outside normal operating range. Sensor malfunctions can sometimes trigger false readings, but the majority of CHECK SOON codes indicate a developing issue that will worsen if left unaddressed. Use a diagnostic scan tool to verify sensor readings before replacing expensive parts.
Can I diagnose this without a scan tool?
Basic visual inspection can be performed without a scan tool — check wiring harnesses for chafing, connectors for corrosion, and related components for physical damage. However, to verify the fault, view live sensor data, and confirm the repair, a heavy-duty diagnostic scan tool (or a compatible OBD-II adapter with J1939/J1708 support) is strongly recommended for accurate diagnosis.
How soon should I schedule service?
Schedule service within the next 1–3 operating days. While the vehicle can continue operating normally, delaying repair increases the risk of the fault escalating to CHECK NEXT STOP severity. Additionally, some CHECK SOON conditions are precursors to emissions system faults that will trigger a mandatory derate if not addressed in a timely manner.
Related Fault Codes — A26
SPN 111 FMI 18
🔴 STOP ENGINE
SPN 641 FMI 5
SPN 3050 FMI 9
Associated Symptoms
References & Further Reading
- SAE J1939-73: Application Layer — Diagnostics. SAE International. Defines SPN N/A / FMI N/A fault code semantics for heavy-duty CAN networks. SAE J1939 Standard
- SAE J1587: Electronic Data Interchange Between Microcomputer Systems in Heavy-Duty Vehicle Applications. SAE International. Defines MID 128 parameter identification protocol. SAE J1587 Standard
- International A26 Service Manual: OEM diagnostic procedures for Engine Coolant Level Sensor faults. Consult the official International service documentation for your specific engine serial number.
- TMC RP 1210: Recommended Practice for Windows-Based Vehicle Diagnostic Interface. Technology & Maintenance Council (TMC) of American Trucking Associations.