TSB 93-6-35: Cooling Fan Relay - Revised Wiring Schematic

Details

Bulletin Number: 93-6-35 Reference Number: 316503 Publish Date: 4/93 Subject: SERVICE MANUAL UPDATE - SECTION 6E3 COOLING FAN RELAY WIRING SCHEMATIC CORRECTION Models Affected: 1993 GRAND PRIX MODELS (VIN X - RPO LQ1) 1993 Grand Prix (VIN X - RPO LQ1) Cooling Fan Relay # 1 wiring schematic as shown is incorrect for Chart C-12 Section 6E3. Primary Cooling Fan Control Relay # 1 Terminals 2 and 3, Circuit 1444 (Red), should be shown spliced together. CHART C-1 2 (Part 1 of 2) COOLING FAN CONTROL DIAGNOSIS 3.4L (LQ1) "W" CARLINE (MFI) Circuit Description: The primary and secondary electric cooling fan(s) are controlled by the ECM based on inputs from the Engine Coolant Temperature (ECT) sensor, the A/C control switches, vehicle speed and state of the A/C refrigerant pressure sensor. The ECM controls the fan(s) by grounding CKT 335 and/or CKT 473, which energizes the fan control relay . Battery voltage is then supplied to the fan motor. The ECM grounds CKT 335 and/or CKT 473, when engine coolant temperature is over about 106~C (223~F), or when A/C has been requested and the A/C pressure is about 1380 kPa (200 psi). Once the ECM turns the relay "ON," it will keep it "ON" for a minimum of 30 seconds or until vehicle speed exceeds 70 mph (40 mph for secondary fan). Also, if DTC 14 or 15 sets, or the ECM is in back up, the primary fan will run at all times. Test Description: Number(s) below refer to circled number(s) on the diagnostic chart. 1. With the diagnostic terminal is grounded, the cooling fan control driver(s) will close, which should energize the fan control relay (s). 2. If the A/C pressure is above 300 psi (2069 kPa) or the circuit is open, the fan would run whenever A/C is requested. 3. With A/C clutch engaged and the A/C refrigerant pressure sensor is functioning properly, the fan should come "ON" when pressure exceeds about 1380 kPa (200 psi). This signal should cause the ECM to energize the fan control relay (s). 4. This will determine if the A/C refrigerant pressure sensor is faulty or if the ECM or circuitry is faulty. Diagnostic Aids: If the owner complained of an overheating problem, it must be determined if the complaint was due to an actual boil over, a hot light, or temp. gauge indicated over heating. If the gauge or light indicates overheating, but no boil over is detected, the gauge circuit should be checked. The gauge accuracy can also be checked by comparing the engine coolant temperature sensor reading using a Tech I scan tool and comparing its reading with the gauge reading. If the engine is actually overheating, and the gauge indicates overheating but the cooling fan is not coming "ON," the coolant sensor has probably shifted out of calibration and should be replaced. If the engine is overheating, and the cooling fan is "ON," the cooling system should be checked. CHART C-12 (Part 2 of 2) COOLING FAN CONTROL DIAGNOSIS 3.4L (LQ1) "W" CARLINE (MFI) Test Description: Number(s) below refer to circled number(s) on the diagnostic chart. 1. 12 volts should be available to CKT 250 and CKT 1444 on each relay when the ignition is "ON." 2. This test checks the ability of the ECM to ground CKT 335 (CKT 473). The MIL (Service Engine Soon) should also be flashing at this point. If it isn't flashing, refer to CHART A-2. 3. If the fan does not turn "ON" at this point, CKT 702, CKT 532 or CKT 150 is open, or the cooling fan motor(s) are faulty.