SPN 4237, FMI 0 - Adaptive Lean Bank 1 High (Gasoline) Diagnostic Aids NOTE: If any other DTCs are present, diagnose those first. Oxygen Sensor Wire - Sensor may be mispositioned contacting the exhaust. Check for short to ground between harness and sensor and on sensor harness Vacuum Leaks - Large vacuum leaks and crankcase leaks can cause a lean exhaust condition at light load. Injectors - System will be lean if an injector driver or driver circuit fails. The system will also be lean if an injector fails in a closed manner or is dirty. Fuel Pressure - System will be lean if fuel pressure is too low. Check fuel pressure in the fuel rail during key-on, engine off and during normal operating conditions. Air in Fuel - If the fuel return hose/line is too close to the fuel supply pickup in the fuel tank, air may become entrapped in the pump or supply line causing a lean condition and driveability problems. Exhaust Leaks - If there is an exhaust leak, outside air can be pulled into the exhaust and past the O2 sensor causing a false lean condition. Fuel Quality - A drastic variation in fuel quality may cause the system to be lean including oxygenated fuels. System Grounding - ECM and engine must be grounded to the battery with very little resistance allowing for proper current flow. Faulty grounds can cause current supply issues resulting in many undesired problems. If all tests are OK, replace the HO2S sensor with a known good part and retest.
Indmar Products
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All Rights Reserved Draft Rev. A-Jan. 2008
