GeekDIYMechanic - Computer Control Systems Overview ScannerDanner - Understanding Short Term and Long Term Fuel Trim Schrodingers Box - Secret of Engine Problem Diagnosis- Fuel Trims Pt.1| Fuel Trim @ Idle | Fuel Trim @ 2500 | Possible Causes |
| Rich(positive) | Normal | Intake vacuum leak after MAF |
| Good | Rich | Low fuel volume |
| Rich | Rich | Low fuel pressure |
| Lean(negative) | Good | Contaminated crankcase |
| Lean(negative) | Lean(negative) | Leaking injector or other sensor causing excessive fuel |