P1620 - FAULT CODE - OBD2

P1620 BUICK, CADILLAC, CHEVROLET, GMC: LOW ENGINE COOLANT CIRCUIT CONDITIONS

The vehicle’s engine cooling system is designed not only to keep the engine cool but also to keep the engine temperature warm enough to ensure proper operation.

Among the components of this system we can mention the radiator that dissipates the heat, the fan or fans that ensure the necessary airflow to achieve the cooling of the radiator, the thermostat valve, which opens when a certain operating temperature is reached, and the water pump or coolant pump that allows the circulation of the coolant through the engine.

This system also includes the Engine Coolant Temperature Sensor, also known as Engine Coolant Switch. This device is part of engine management and helps to control the engine coolant temperature. Generally, this switch works by using an electrical resistor to measure the temperature. This information is then sent to the PCM who, based on this data, will make the respective adjustments in engine timing and fuel calculations for optimum performance, since engines require more fuel when they are cold and the opposite occurs when their temperature is high.

DTC P1620 OBDII is set by the Powertrain Control Module when it detects that while the engine is running the engine coolant switch signal is low for about 20 seconds. This condition indicates an open circuit.

• Check Engine lamp illumination.
• Increased fuel consumption.
• Expulsion of black smoke from the exhaust.
• Increased engine temperatures.

The reasons for setting the P1620 OBD2 diagnostic code are:

• The Coolant Temperature Switch circuit possibly has damage to its wiring.
• The Engine Coolant Switch/Engine Coolant Temperature Sensor connections may have deficiencies causing an open circuit.
• The Coolant Temperature Switch may be defective.

To troubleshoot the P1620 OBDII fault code you must do the following:

• Consult the Technical Service Bulletins.
• Check the wiring and connectors of the Coolant Temperature Switch circuit and check them for common damage. Repair if you discover conditions that interfere with proper operation.
• Measure the Engine Coolant Switch/Engine Coolant Temperature Sensor circuit voltages and check that they match the manufacturer's specifications. If you discover a short, check that it is not due to damage to the connections or the switch itself. Make the appropriate corrections.