Notes On Intermittents

Engine running, manipulate the oxygen sensor and ECM wiring and connectors while observing ECM Data ED33. If the fault is induced, ED33 will jump above 0.63 volts and the "ECON" status light will go on. Manipulate CKT 413 ground to the engine and look for a loose ground eyelet or ground eyelet installed at wrong location. Check oxygen sensor connector terminals for signs of corrosion or foreign material. Clean if signs of corrosion are evident. If rich engine operation is suspected, perform PFI SYSTEM CHECK  . See TROUBLE SHOOTING - NO CODES article "Poor Fuel Economy" and "Excessive Exhaust Emissions" If the oxygen sensor circuit appears to be OK, go to PFI CHART A-11: LEFT O2 SENSOR RICH  to check for faulty or contaminated sensor.