Diagnostic Aids
- If the owner complained of an overheating problem, it must be determined if the complaint was due to an actual boil over, or the engine coolant temperature gauge indicated overheating. If the engine is overheating and the cooling fans are on, the cooling system should be checked.
- If the engine fuse block fuses Ef6 become open (blown) immediately after installation, inspect for a short to ground in the wiring of the appropriate circuit. If the fuses become open (blown) when the cooling fans are to be turned on by the ECM, suspect a faulty cooling fan motor.
- The ECM will turn the cooling fans on at low speed when the coolant temperature is 97°C (207°F). The ECM will turn the cooling fans off when the coolant temperature is 94°C (201°F).
- The ECM will turn the cooling fans on at high speed when the coolant temperature is 101°C (214°F). The ECM will change the cooling fans from high speed to low speed when the coolant temperature is 98°C (208°F).
- The ECM will turn the cooling fans on at low speed when the A/C system is ON. The ECM will change the cooling fans from low speed to high speed when the high side A/C pressure is 1,882 kPa (273 psi) then return to low speed when the high side A/C pressure is 1,448 kPa (210 psi). When the A/C system is ON, the ECM will change the cooling fans from low to high speed when the coolant temperature reaches 117°C (244°F) then return to low speed when the coolant temperature reaches 114°C (237°F).
- The cooling fan circuit can be checked quickly by disconnecting the ECM connector 2 and grounding the connector terminal C50. This should create low speed cooling fan operation with the ignition ON. By grounding the ECM connector terminals C50 and E34 and turning the ignition ON, high speed cooling fan operation should be achieved.