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Home >> Mitsubishi >> 1995 >> Eclipse GS, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes - 2.0L Turbo >> Diagnostic Tests >> Code P0170: Fuel Trim Fault

Code P0170: Fuel Trim Fault

NOTE: For component terminal identification, see TERMINAL IDENTIFICATION  in this article. For appropriate WIRING DIAGRAMS, see WIRING DIAGRAMS  section.
  1. Using scan tool, read SERVICE DATA No. 13 (intake air temperature sensor). If temperature displayed on scan tool is equal to actual air temperature, go to next step. If temperature displayed on scan tool is not equal to actual air temperature, check air temperature circuit. See CODE P0110: INTAKE AIR TEMPERATURE FAULT  .
  2. Using scan tool, read SERVICE DATA No. 21 (coolant temperature sensor). If temperature displayed on scan tool is equal to actual coolant temperature, go to next step. If temperature displayed on scan tool is not equal to actual coolant temperature, check coolant temperature circuit. See CODE P0115: COOLANT TEMPERATURE CIRCUIT FAULT  .
  3. Using scan tool MUT II mode, read SERVICE DATA No. 25 (barometric pressure sensor). Reading should be 101 kPa at 0 ft. (0 m), 95 kPa at 1969 ft. (600 m), 88 kPa at 3937 ft. (1200 m) or 81 kPa at 5906 ft. (1800 m). If scan tool reading is within specification, go to next step. If scan tool reading is not within specification, check barometric pressure circuit. See CODE P0105: BAROMETRIC PRESSURE CIRCUIT FAULT  .
  4. Disconnect fuel injector connector. Measure resistance between fuel injector terminals. If resistance is 2-3 ohms at 68°F (20°C), go to next step. If resistance is not 2-3 ohms at 68°F (20°C), replace fuel injector.
  5. Using stethoscope, check injector operating sound during cranking or at idle. Check that frequency of operating sound increases as engine RPM increases. If injectors are okay, go to next step. If no operating sound is heard from an injector, check injector drive circuit. If drive circuit is okay, injector or PCM is suspect.
  6. Check fuel injector connectors, PCM connector and wiring harness between PCM and injector connectors. If wiring and connectors are okay, start and warm engine. Turn all accessories off. Increase engine speed to 2500 RPM. Using scan tool, read SERVICE DATA No. 81 (long-term fuel compensation). If fuel trim is less than zero (during closed loop), go to next step. If fuel trim is more than zero (during closed loop), go to step  8 .
  7. Read SERVICE DATA No. 12 (volume airflow sensor). Reading should be from 22-48 Hz at idle to 60-100 Hz at 2500 RPM. Check that frequency (airflow volume) increases as RPM is increased. If scan tool reading is more than specification, replace volume airflow sensor. If scan tool reading is not more than specification, replace PCM.
  8. Check air induction system for leaks or obstructions. If air intake system is okay, read SERVICE DATA No. 12 (volume airflow sensor). Reading should be from 22-48 Hz at idle to 60-100 Hz at 2500 RPM. Check that frequency (airflow volume) increases as RPM is increased. If scan tool reading is more than specification, replace volume airflow sensor. If scan tool reading is not more than specification, replace PCM.
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