For 1990-2009 cars

### Circuit Description

The PCM monitors the 12 volt signal from the low coolant switch. When the switch opens, indicating a low coolant condition, the PCM will not detect the 12 volt signal.

### Conditions for Setting the DTC

Important: The low coolant circuit is continuously checked when the engine is running.

DTC P1620 will set if the coolant switch opens, low signal, for 20 seconds with the engine running.

### Diagnostic Aids

• | DTC P1620 will set during cooling fan run-on. In high coolant temperature conditions, the cooling fan stays on up to 4 minutes after the ignition is turned OFF. To verify this condition, observe IGN volts in the DTC P1620 failure record. If IGN volts is less than 2 volts, the DTC was caused by cooling fan run-on. DTC P1620 should be cleared and the vehicle returned to the customer.

• | The low coolant switch is located in the coolant recovery tank and is a normally closed switch when the coolant bottle is at the proper level.

• | Pressure check the system for leaks. Refer to the Engine Cooling section of the Engine/Fuel/Air Intake/Exhaust Service Manual.

• | The switch is normally closed when the coolant bottle is full.

• | The low coolant/hot light will flash when the coolant switch is open.