Diagnostic Aids
After engine is started, engine coolant temperature should rise to approximately 194°F (90°C) and stabilize when thermostat opens. If engine is allowed to cool overnight, coolant temperature and Manifold Air Temperature (MAT) should read nearly the same with a scan tester. When Code 14A is set, the ECM turns on the cooling fan. Code 14A results if circuit No. 410 is shorted to ground. For intermittent inspection, see INTERMITTENTS in TROUBLE SHOOTING - NO CODES - FUEL INJECTION article.