Troubleshooting Trees
Interactive Troubleshooting Trees
Systematic, step-by-step diagnosis for the four major diesel truck systems. Follow the decision tree from symptom to root cause — no guesswork.
Aftertreatment Troubleshooting Tree
DPF, SCR, DEF, DOC — systematic diagnosis from symptom to root cause
SPN 5246 FMI 31SPN 4364 FMI 18SPN 3251 FMI 0SPN 3719 FMI 16
Start Diagnosis Fuel System Troubleshooting Tree
Rail pressure, injectors, fuel pump, IMV — low power and hard start diagnosis
SPN 157 FMI 18SPN 729 FMI 2SPN 1347 FMI 7SPN 1637 FMI 2
Start Diagnosis Turbo / Air Handling Troubleshooting Tree
VGT, boost pressure, EGR, air filter — derate and low power diagnosis
SPN 641 FMI 7SPN 102 FMI 4SPN 1127 FMI 16SPN 4237 FMI 16
Start Diagnosis Electrical / J1939 Troubleshooting Tree
CAN bus, battery voltage, ECM, sensor circuits — communication and power faults
SPN 625 FMI 9SPN 168 FMI 2SPN 625 FMI 12SPN 91 FMI 3
Start Diagnosis Need AI-Guided Diagnosis?
The troubleshooting trees cover common paths. For complex multi-system faults, the AI Diagnostic Engine provides a fully guided diagnosis.
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