Electric Cooling Fan Diagnosis

Electric Cooling Fan Diagnosis:

Electric Cooling Fan Diagnosis (continued):

Engine Controls (Cooling Fans):

CIRCUIT DESCRIPTION

Power is supplied to the cooling fan motors through a fusible link and three 60 amp maxifuses. The relay coils are energized when the Powertrain Control Module (PCM) completes the ground path. The PCM Output Driver Module (ODM) B output 1 is grounded for Fan 1 operation. PCM ODM B output 2 is grounded for Fan 2 operation.

During Fan 1 operation the PCM supplies a ground path for the Fan 1 relay through ODM B output 1. This closes Fan 1 relay contacts and current flows from the battery junction block through the relay and to the primary cooling fan. The primary cooling fan is grounded at the engine block.

During Fan 2 operation the PCM keeps Fan 1 energized and supplies a ground path for the Fan 2 relay through ODM B output 2. This closes Fan 2 relay contacts and current flows through Fan 2 to engine ground.

DIAGNOSTIC AIDS

Check for the following conditions:

^ Poor connection at the PCM, cooling fan relays, or cooling fan motors. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.

^ Damaged harness. Inspect the wiring harness for damage.

TEST DESCRIPTION

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

2. Stored Diagnostic Trouble Codes (That may not illuminate the Malfunction indicator Lamp) may enable the engine cooling fans. This Diagnostic Table may lead to improper diagnosis and replacement of good parts if Diagnostic Trouble Codes are present.

6. Ambient temperature must be above 9°C (48°F) before the PCM will enable the cooling fans due to A/C request. The PCM will enable the cooling fans if A/C refrigerant pressure increases regardless of ambient temperature.