If a driveability condition still exists after following the Powertrain OBD system check and reviewing the Symptoms tables, a sensor that is stuck in range may be the cause. In the case of a sensor or circuit malfunction, the ECM will replace sensed values with calibrated default values. This feature allows limited engine performance until the condition is repaired. If a sensor is stuck within the normal operating range, the condition may go undetected by the ECM, and could result in a driveability concern. A basic understanding of sensor operation is necessary in order to diagnose a sensor that is stuck in range.

An example of a sensor that is stuck in range would be if the coolant sensor is reading 10°C (50°F), but the actual coolant temperature is 66°C (150°F). This condition would cause the ECM to deliver more fuel than is actually required by the engine. This would result in an overly rich condition, and cause the engine to run rough. This condition would not set a diagnostic trouble code (DTC), because the ECT value is within the normal operating range. To help identify a sensor that is stuck in range, operate the engine under various conditions, while observing the appropriate scan tool parameter. The parameter value should vary as engine temperature, engine speed, or load is varied.

Resistance on a low reference circuit, or signal circuit may also cause a sensor value to be incorrect. If this condition is suspected, disconnecting the sensor and testing the circuits may isolate the condition. Refer to the appropriate Circuit/System Testing procedure for the applicable sensor to assist in testing the circuit.