International (Navistar)
J1939 SPN/FMI
SPN 1659 / FMI 20
International Fault Code SPN 1659 FMI 20: ECT1 Below Expected – Check Thermostat
SPN 1659 FMI 20 on International / Navistar trucks means: ECT1 Below Expected – Check Thermostat.
Code details
- Manufacturer
- International (Navistar)
- Applies to
- International MaxxForce DT (2010–2019)
- Fault code
- SPN 1659 FMI 20
- J1939 SPN
- 1659
- FMI
- 20
- Truck models in source
- 3200, 4100, 4300, 4400, 7300, 7400, 7500, 7600, 7700, 8500, 8600, BE 200, CE Bus, CXT, DuraStar, LoneStar, MXT, ProStar, RXT, TranStar, WorkStar
What to do next
- Read active and inactive codes with the OEM service tool (Diamond Logic Builder can clear previously active codes) and note the occurrence count.
- FMI 20 tells the shop the type of failure to test for: .
- Have a heavy-duty diesel technician confirm the fault against the engine or chassis service manual before replacing parts.
Get this code diagnosed
Send one request and nearby diesel shops and mobile mechanics can quote the repair.
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Related fault codes
- International Fault Code SPN 1659 FMI 14 — Engine Coolant System Thermostat 1: Special Instructions
- International Fault Code SPN 1659 FMI 18 — Engine Coolant System Thermostat 1: Data Valid But Below Normal Operating Range – Moderately Severe Level
- PACCAR Fault Code P2181 — Engine Coolant Temperature – Does Not Match Engine Operating Conditions
Source: International MaxxForce DT 2010–2019 fault code list (Diesel Laptops). See also OBD-II codes.