ford escort 2001April 22, 2014April 22, 2014codes only go up to 0900 something and my code reads 1131 Keywords:code 1131escort 1 thought on “ford escort 2001” Freeautomechanic April 22, 2014 at 4:48 pm P1131 Lack Of HO2S11 Switch – Sensor Indicates Lean Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 1 Reference Link: http://www.freeautomechanic.com/diagnostictroblecodes.html Possible causes – Faulty Oxygen Sensor – Vacuum leak affecting bank 1 only – Fuel injector problem bank 1 – Check for cylinder misfire on bank 1 – Engine mechanical condition Tech notes Though the Oxygen (O2) sensor, the Engine Control Module (ECM) has detected a lean system, which means that there is either not enough fuel or and excessive amount of air in the system. Start by checking for vacuum leaks. ——————————————————- A Heated Exhaust Oxygen (HO2S) sensor indicating rich at the end of a test is trying to correct for an over-lean condition. The test fails when the fuel control system no longer detects switching for a calibrated amount of time. Comments are closed.