Powertrain Diagnosis

Diagnostic Chart:

Wiring Diagram:

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.

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

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

DIAGNOSTIC AIDS
^ DTC P1620 will set during cooling fan run-on. (In high coolant temp conditions, the cooling fan stays on up to 4 minutes after the ignition is turned off.) To verify this condition, observe ION volts in the DTC P1620 failure record. If ION 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 proper level.
^ Pressure check system for leaks. refer to "Engine Cooling" section of the "Engine/Fuel/Air Intake/Exhaust Service Manual."
^ Normally closed switch when coolant bottle is full.
^ The Low Coolant/HOT light will flash when coolant switch is open.