Diagnostic Aids

If engine is allowed to cool overnight, coolant and IAT sensor values should be close to each other when measured by scan tester Check sensor for shifted calibration by using sensor TEMPERATURE VS RESISTANCE VALUES table.

Fig 1: Code 37 Schematic (4.0L) IAT Sensor Circuit Shorted High Temperature Indicated

Fig 2: Code 37 Diagnostic Flow Chart (4.0L) TCC Brake Switch Error