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MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS TSB Revision MULTIPORT FUEL INJECTION (MFI) <3.0L> 13B-447 Judgment Criteria • Long-term fuel trim has continued to be higher than +12.5 percent for 5 seconds. or • Short-term fuel trim has continued to be higher than +7.4 percent for 5 seconds. Check Conditions • Engine coolant temperature is lower than approx- imately 100 °C (212°F) when the engine is started. • Intake air temperature is lower than 60°C (140°F) when the engine is started. • Under the closed loop air/fuel ratio control. • Engine coolant temperature is higher than 77°C (171 °F). • Volume airflow sensor output frequency is 75 Hz or less. Judgment Criteria • Long-term fuel trim has continued to be higher than +12.5 percent for 5 seconds. or • Short-term fuel trim has continued to be higher than +12.5 percent for 5 seconds. Check Conditions • Engine coolant temperature is higher than approximately 100 °C (212°F) when the engine is started. • Intake air temperature is higher than 60°C (140 °F) when the engine is started. • Under the closed loop air/fuel ratio control. • Engine coolant temperature is higher than 77°C (171 °F). • Volume airflow sensor output frequency is 75 Hz or more. Judgment Criteria • Long-term fuel trim has continued to be higher than +12.5 percent for 5 seconds. or • Short-term fuel trim has continued to be higher than +17.6 percent for 5 seconds. Check Conditions • Engine coolant temperature is higher than approximately 100 °C (212°F) when the engine is started. • Intake air temperature is higher than 60°C (140 °F) when the engine is started. • Under the closed loop air/fuel ratio control. • Engine coolant temperature is higher than 77°C (171 °F). • Volume airflow sensor output frequency is 75 Hz or less. Judgment Criteria • Long-term fuel trim has continued to be higher than +12.5 percent for 5 seconds. or • Short-term fuel trim has continued to be higher than +22.3 percent for 5 seconds. Check Conditions • Engine coolant temperature is higher than 77°C (171 °F). • Under the closed loop air/fuel ratio control. Judgment Criteria • Long-term fuel trim has continued to be +12.5 percent for 5 seconds. or • Short-term fuel trim has continued to be +25.0 percent for 5 seconds. . OBD-ll DRIVE CYCLE PATTERN − OBD-ll Drive Cycle − Procedure 2 − Fuel Trim Monitor . TROUBLESHOOTING HINTS (The most likely • Volume airflow sensor failed. • Injector (Number 1, 3, 5) failed. • Incorrect fuel pressure. • Air drawn in from gaps in gasket, seals, etc. • Right bank heated oxygen sensor failed. • Engine coolant temperature sensor failed. • Intake air temperature sensor failed. • Barometric pressure sensor failed. • Use of incorrect or contaminated fuel. • Harness damage in right bank injector circuit, or connector damage. • ECM failed. <M/T> • PCM failed. <A/T> DIAGNOSIS Required Special Tools: • MB991958: Scan Tool (MUT-III Sub Assembly) • MB991824: V.C.I. • MB991827: USB Cable • MB991911: Main Harness B |