For 1990-2009 cars

Step | Action | Yes | No
--- | --- | --- | ---
Schematic Reference: Engine Cooling Schematics Connector End View Reference: Cooling System Connector End Views DEFINITION: The check coolant level display is always on when the key is in the ON position.
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 |

1. Turn the ignition switch ON, with the engine OFF.
2. With a scan tool, observe the low coolant switch parameter in the climate control panel HVAC system data list.

Does the low coolant switch display open?

Go to Step 3

Go to Testing for Intermittent Conditions and Poor Connections

3 |

1. Disconnect the coolant level switch connector.
2. Connect a 3 A fused jumper wire between the coolant level switch signal circuit and the coolant level switch ground circuit, at the harness connector of the coolant level switch.

Does the low coolant switch display CLOSED on the scan tool?

Go to Step 7

Go to Step 4

4 | Connect a 3 A fused jumper wire from the coolant level switch signal circuit at the coolant level switch harness connector to a good ground. Does the low coolant switch display CLOSED on the scan tool? | Go to Step 6 | Go to Step 5
5 | Test the signal circuit of the coolant level switch for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the problem? | Go to Step 11 | Go to Step 8
6 | Repair the open or high resistance in the coolant level switch ground circuit. Refer to Wiring Repairs . Did you complete the repairs? | Go to Step 11 | --
7 | Inspect for poor connections at the harness connector of the coolant level switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the problem? | Go to Step 11 | Go to Step 9
8 | Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the problem? | Go to Step 11 | Go to Step 10
9 | Replace the coolant level switch. Refer to Radiator Surge Tank Replacement . Did you complete the replacement? | Go to Step 11 | --
10 | Replace the HVAC control module. Refer to Control Module References for replacement, setup, and programming. Did you complete the repairs? | Go to Step 11 | --
11 | Operate the system in order to verify the repairs. Did you correct the problem? | System OK | Go to Step 2