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DTC P1128/17536 - Long Term Fuel Trim Too Lean

NOTE: DTC sets if fuel mixture is so lean than Heated Oxygen Sensor (HO2S) control is on rich limit.
  1. Test drive vehicle for performance problems. If problem occurs only at full acceleration, replace fuel filter. Erase DTC memory and test drive vehicle. See CLEARING DTCS in this article. Recheck DTC memory and verify DTC does not reset. If DTC resets, go to next step. If other performance problem(s) exist, go to next step.
  2. If engine output is impaired at lower throttle openings or vehicle jerks at lower throttle openings, turn engine off. See 2.0L or 2.8L under FUEL INJECTORS & CIRCUIT under FUEL SYSTEM in appropriate SYSTEM/COMPONENT TESTS - GASOLINE article. If fuel injectors and circuit are operating properly, go to next step.
  3. Inspect fuel injectors for poor Electronic Connection or dirty/clogged injectors. If injectors and connections are okay, go to next step. If a malfunction was repaired, erase DTC memory and test drive vehicle. See CLEARING DTCS  in this article. Recheck DTC memory and verify DTC does not reset. If DTC resets, go to next step.
  4. Replace faulty ECM. Test drive vehicle. Recheck DTC memory and verify DTC does not reset. If DTC resets, repeat testing procedure.
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