Code 14B - Cts Circuit (Low Temperature Indicated): Notes

Coolant temperature sensor controls signal voltage to the ECM. The ECM applies voltage on circuit No. D12 to the sensor. When engine is cold, sensor resistance is high and ECM will see a high signal voltage. As engine warms, sensor resistance decreases and ECM will see a low signal voltage. When engine reaches normal operating temperature, signal voltage will be approximately 1.5-2.0 volts at the ECM. Coolant temperature is one of the inputs used to control fuel delivery, Electronic Spark Timing (EST) and Idle Air Control (IAC).

1. Code 14B will set if engine has been running at least 3 minutes and coolant temperature is less than -31°F (-37°C) for 3 seconds.
2. This simulates a Code 14A. If ECM recognizes low signal voltage (high temperature), ECM and wiring are okay.
3. This determines if circuit No. A11 is open. Scan tester should display high temperature.