Circuit Description

While engine is warming, PCM reads Engine Coolant Temperature (ECT) sensor to determine how long it takes coolant to reach temperature required for closed loop operation. PCM compares actual time required to a predetermined time.

Conditions required to set DTC are:

• No IAT or ECT sensor DTCs present.
• IAT is greater than 50°F (10°C).
• Start-up ECT is 50-62°F (10-30°C).
• ECT sufficient to allow "closed loop" operation is not achieved within 2 minutes of start-up.