Coolant Level Switch

Diagnostic Chart:

Wiring Diagram:

DIAGNOSIS

^ The following tables will diagnose the oil level switch, the oil pressure switch and the coolant level switch circuits.

^ For diagnosis of the fuel pump circuitry portion of the fuel pump and engine oil level switch, refer to Engine Cranks but Does Not Run.

^ For diagnosis of the Instrument Panel Cluster (IPC), refer to Instrument Panel, Gauges and Warning Indicators.

^ For PCM replacement information, refer to PCM/EEPROM Replacement/Programming.

CIRCUIT DESCRIPTION

The coolant level switch is an assembly containing a reed switch and magnetic float. When the coolant level is normal, the float rests away from the reed switch, causing the switch to open. When the coolant level is low, the float rests near the reed switch and the switch closes.

The coolant level switch is mounted in the radiator surge tank. If the coolant level falls below a specified level, the switch closes sending a ground signal to the Powertrain Control Module (PCM). The PCM will then send this signal to the Instrument Panel Cluster (IPC). The IPC will then illuminate the low coolant level telltale lamp.

DIAGNOSTIC AIDS

^ Quick test: Disconnect the coolant level switch electrical connector. With a test light connected to ground, probe the signal circuit. This will cause the coolant level indicator to turn ON if the wiring, PCM and IPC are OK.

^ An Intermittent problem may be caused by a poor connection, rubbed through wire insulation.

^ Any circuitry, that is suspected as causing the intermittent complaint, should be thoroughly checked for the following items:

- backed out terminals

- improper mating

- broken locks

TEST DESCRIPTION

Number(s) below refer to the step number(s) on the Diagnostic Table.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored on the scan tool for later reference.

4. The coolant level switch cannot be removed from the surge tank. Draining the coolant from the tank will check it the switch can detect an empty tank and also check the PCM and wiring.

6. A test light is used to determine if the coolant level telltale lamp is remaining ON because of a shorted signal circuit, a faulty PCM, or a faulty IPC. It the test light is ON, then the signal circuit is shorted to ground.

7. This simulates a normal coolant level. If the telltale lamp turns OFF when the coolant level switch is disconnected, then the PCM, the IPC and the wiring are OK.

9. The PCM uses a voltage signal to sense when the coolant signal circuit is pulled low by the coolant switch. If voltage is not present on this the signal circuit, then the circuit is open, or connections or the PCM are faulty.

12. This will determine that the battery voltage seen on the signal circuit was from the PCM and not a wire shorted to voltage.

15. The PCM sends coolant level information through serial data to the IPC. If the scan tool indicates a low coolant level when the coolant level switch electrical connector disconnected, then the PCM is faulty.

19. Replacement PCM's must be reprogrammed. Refer to the latest Techline information for programming procedures.

20. If no faults have been found at this point and no additional DTC's were set, refer to Diagnostic Aids for additional checks and information.