Onan HGJAA-HGJAF (EFI) error code 54 (MAT Sensor Fault)
EFI only. Open or short circuit in MAT sender. Manual threshold: MAT sender input greater than 300k Ohms.
What to check, and in what order, is in the app. The flow Onan Code 54 — MAT (Manifold Air Temperature) Sender Fault walks this code step by step with the pass/fail measurements, wiring schematics and procedures that go with it, and it works offline in the bay.
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- Cummins-Onan Service Manual (document 0983-0501 Issue 26, March 2018, 202 pp) covering HGJAA Spec A-E / HGJAB A-E / HGJAC A-C / HGJAD A-E / HGJAE A-E / HGJAF A-C (rv-tech-resources/25-onan-hgjaa/0983-0501_Onan_HGJAA-HGJAF_Service_Manual_Issue_26.pdf)
- Onan HGJAA Generator Technician Service Diagnostic Reference (rv-tech-resources/25-onan-hgjaa/Onan_HGJAA_Generator_Technician_Service_Diagnostic_Reference.md)
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