Electric Cooling Fans Chevrolet Lumina I

MODEL IDENTIFICATION

BODY CODE DESIGNATIONS

DESCRIPTION

The electric cooling fan is used for radiator and A/C condenser cooling. Cooling fan operates when A/C is on and when engine coolant temperature exceeds a specific value.

3.1L

Powertrain Control Module (PCM) uses primary and secondary electric cooling fan relays to control primary and secondary cooling fans. Secondary cooling fan is used on vehicles with heavy duty cooling with A/C. PCM will energize primary cooling fan when Engine Coolant Temperature (ECT) sensor indicates greater than 223°F (106°C); A/C is requested and vehicle speed is less than 50 MPH; A/C refrigerant pressure is greater than 185 psi (13 kg/cm 2 ); Diagnostic Trouble Codes (DTC) 14, 15 or 70 are set; or PCM is operating in back-up mode.

PCM will energize secondary cooling fan when ECT sensor indicates a temperature greater than 235°F (113°C) with A/C off or on, A/C is requested with vehicle speed less than 40 MPH, or A/C refrigerant pressure is greater than 136 psi (9.6 kg/cm 2 ).

3.4L

Powertrain Control Module (PCM) controls left and right side cooling fans. PCM will energize left side fan (fan No. 1) when engine coolant temperature exceeds 223°F (106°C), when A/C refrigerant pressure is greater than 240 psi (16.9 kg/cm 2 ), or when Diagnostic Trouble Codes (DTC) P0117 or P0118 is set.

PCM will energize right side fan (fan No. 2) when engine coolant temperature exceeds 235°F (113°C); A/C is requested and vehicle speed is less than 40 MPH; or when A/C refrigerant pressure is greater than 240 psi (16.9 kg/cm 2 ).

3.8L

Powertrain Control Module (PCM) controls left side cooling fan (fan No. 1) and right side cooling fan (fan No. 2). PCM will energize left side cooling fan when engine coolant temperature exceeds 212°F (100°C) or when A/C is requested. Cooling fan will continue to run about 45 seconds after A/C request signal is gone.

When left side cooling fan is energized, PCM will delay right side cooling fan for approximately 6 seconds. When A/C refrigerant pressure exceeds 210 psi (14.8 kg/cm 2 ), PCM will energize right side cooling fan. PCM will also energize right side cooling fan when engine coolant temperature exceeds 226°F (108°C).

TROUBLE SHOOTING

Note. This article contains test charts which are part of General Motors Computerized Engine Controls. Only those charts required to test electric cooling fans are included. Other diagnostic information may be referenced while performing electric cooling fan diagnosis. For complete information on General Motors Computerized Engine Control systems, see the G-TESTS W/CODES article in the ENGINE PERFORMANCE section.

Trouble shoot cooling fan using appropriate C-12 charts provided. See COOLING FAN CHART INDEX table. For cooling fan relay location, see COOLING FAN RELAY LOCATION table.

COOLING FAN RELAY LOCATION

COOLING FAN CHART INDEX

COOLING FAN CHART INDEX

SCAN TESTER

A variety of information is transmitted through Data Link Connector (DLC) terminal "E" or "M" depending on engine. This data is transmitted at a high frequency which requires a Tech 1 scan tester for interpretation. Several scan testers are available for diagnostic work. Scan testers other than Tech 1 scan tester will function and provide information for diagnostic work; however, some charts will specify a Tech 1 scan tester. Failure to use a Tech 1 scan tester, when specified, may result in incorrect diagnosis of a system.

CHART C-12 - COOLING FAN CIRCUIT DIAGNOSIS - 3.1L - VIN M (1 OF 2)

Battery voltage is supplied to primary cooling fan relay No. 1 by circuit No. 342. (Scheme 1) Ignition voltage to energize primary cooling fan relay No. 1 is supplied by circuit No. 540. When Powertrain Control Module (PCM) grounds circuit No. 335, relay is energized and cooling fan is turned on. When engine is running, PCM will energize primary cooling fan if Diagnostic Trouble Code (DTC) 14, 15 or 70 is set; A/C is requested and vehicle speed is less than 50 MPH; engine coolant temperature is greater than 226°F (108°C) with A/C off, 223°F (106°C) with A/C on; or A/C refrigerant pressure is greater than 187 psi (13.1 kg/cm 2 ). If referred to a C-10 chart, see the C-10 chart in the A/C COMPRESSOR CLUTCH CONTROLS article.

Diagnostic Aids

If an overheating condition is suspected, check if it is caused by an actual boilover. If gauge or light indicates an overheat condition and boilover is not evident, inspect gauge circuit for malfunction.

If vehicle is overheating and gauge or light indicates so but cooling fan is not coming on, check Engine Coolant Temperature (ECT) sensor temperature using a scan tester. ECT sensor may have shifted out of calibration and should be replaced. If engine is overheating and cooling fan is on, check cooling system.

Scheme 1

Scheme 2

CHART C-12 - COOLING FAN CIRCUIT DIAGNOSIS - 3.1L - VIN M (2 OF 2)

Battery voltage is supplied to secondary cooling fan relay No. 2 by circuit No. 1442. Ignition voltage to energize primary cooling fan relay No. 2 is supplied by circuit No. 241. When A/C compressor clutch is energized by selecting A/C or defrost, relay is energized and secondary cooling fan is turned on. Powertrain Control Module (PCM) will energize secondary cooling fan if A/C is requested and vehicle speed is less than 50 MPH, engine coolant temperature is greater than 235°F (113°C), or if A/C refrigerant pressure is greater than 136 psi (9.6 kg/cm 2 ).

If a poor A/C cooling condition exists, check for low A/C refrigerant charge, Diagnostic Trouble Code (DTC) 66 or 70 set, or faulty secondary cooling fan.

Scheme 3

CHART C-12A - COOLING FAN CIRCUIT DIAGNOSIS (1 OF 4) 3.4L - VIN X

Power for fan motors comes from 60-amp fuse to relays. Fan relays are energized when a ground circuit is completed through Powertrain Control Module (PCM) quad-driver. (Scheme 4) PCM energizes left cooling fan (fan No. 1) through PCM terminal A2 when Engine Coolant Temperature (ECT) sensor indicates 223°F (106°C) or when A/C is requested. PCM energizes right cooling fan (fan No. 2) if A/C refrigerant pressure reaches 240 psi (16.9 kg/cm 2 ) or ECT sensor indicates 235°F (113°C).

Note. Test numbers refer to numbers on diagnostic charts. (Scheme 5)

1. Selecting Tech 1 miscellaneous tests, FAN 1, causes PCM to ground circuit No. 335. Left cooling fan (fan No. 1) should run.
2. Selecting Tech 1 miscellaneous tests, FAN 2, allows control of circuit No. 473. Right cooling fan (fan No. 2) should run.

Scheme 4

Scheme 5

CHART C-12B - COOLING FAN ON AT ALL TIMES (2 OF 4) 3.4L - VIN X

Note. Test numbers refer to numbers on diagnostic charts. (Scheme 6)

1. Checks if circuit No. 335 is shorted to ground, which would keep relay closed at all times.
2. Checks if circuit No. 473 is shorted to ground. If test light comes on, wire is shorted to ground. Continuing with chart diagnosis will isolate short.
3. If test light is off after disconnecting PCM, ensure circuit No. 473 is not shorted to battery voltage. If circuit is not shorted to battery voltage, PCM is shorted internally.
4. If test light is off after disconnecting PCM, ensure circuit No. 335 is not shorted to battery voltage. If circuit is not shorted to battery voltage, PCM is shorted internally.

Scheme 6

CHART C-12C - COOLING FAN NO LEFT SIDE FAN (3 OF 4) 3.4L - VIN X

Note. Test numbers refer to numbers on diagnostic charts. (Scheme 7)

1. Checks for battery voltage at relay harness connector terminals B4 and B6.
2. Jumpering relay terminals B6 and C4 by-passes relay, which should cause fans to run if fan motors and wiring are okay.
3. Select Tech 1 miscellaneous tests, FAN 1. Turn fans on. PCM should ground circuit No. 335. At this point, test light should be on if PCM is good and circuit No. 335 is not open.
4. Checks for battery voltage and ground to fan motor. Test light on at this point indicates a faulty fan motor connection or motor.

Scheme 7

CHART C-12D - COOLING FAN NO RIGHT SIDE FAN (4 OF 4) 3.4L - VIN X

Note. Test numbers refer to numbers on diagnostic charts. (Scheme 8)

1. Checks for battery voltage at relay harness connector terminals B8 and B10.
2. Jumpering relay harness terminals B10 and C8 by-passes right fan relay (fan No. 2). If fan runs, fan relay is faulty.
3. Checks circuit No. 473 back to PCM. If circuit No. 473 is okay, right fan relay (fan No. 2) is faulty.
4. Checks wiring to fan No. 2 motor. If wiring is okay, problem is poor connections, open ground circuit or faulty fan No. 2 motor.

Scheme 8

An intermittent may be caused by a poor connection, rubbed-through wire insulation or a wire broken inside the wire insulation. Check PCM harness connector for backed-out terminals. Connect a DVOM between affected terminal and ground. Wiggle related wires and connectors while watching DVOM for a voltage reading change. Ensure ECT sensor is not mis-scaled. See Diagnostic Trouble Code (DTC) P0117 chart in the G-TESTS W/CODES article in the ENGINE PERFORMANCE section. Ensure engine cooling system functions properly.

CHART C-12A - COOLING FAN CIRCUIT DIAGNOSIS (1 OF 4) 3.8L - VIN L

Right side cooling fan (fan No. 2) is a low and high speed fan. Left side cooling fan (fan No. 1) is a low speed fan. Power for fan motor goes through a 60-amp fuse. (Scheme 9) Fan relays are energized when a ground circuit is completed through Powertrain Control Module (PCM) quad-driver. PCM energizes left side cooling fan (fan No. 1) through PCM terminal B22 when Engine Coolant Temperature (ECT) sensor indicates 212°F (100°C) or when A/C is requested. PCM energizes right side cooling fan (fan No. 2) if A/C refrigerant pressure reaches 210 psi (14.8 kg/cm 2 ) or ECT sensor indicates 226°F (108°C).

Note. Test numbers refer to numbers on diagnostic charts. (Scheme 10)

1. Select Tech 1 miscellaneous tests, FAN 1. Turn fan on. PCM should ground circuit No. 335. Left side cooling fan (fan No. 1) should run.
2. Selecting Tech 1 miscellaneous tests, FAN 2, allows control of circuit No. 473. Right side cooling fan (fan No. 2) should run.
3. Disconnecting A/C head switch should cause both fans to run.

Scheme 9

Scheme 10

CHART C-12B - COOLING FAN ON AT ALL TIMES (2 OF 4) 3.8L - VIN L

Note. Test numbers refer to numbers on diagnostic charts. (Scheme 11)

1. Checks if circuit No. 473 is shorted to ground. If test light comes on, wire is shorted to ground. Continuing with chart diagnosis will isolate short.
2. Checks if circuit No. 335 is shorted to ground, which would keep relay closed at all times.
3. If test light is off after disconnecting PCM, ensure circuit No. 335 is not shorted to battery voltage. If circuit is not shorted to battery voltage, PCM is shorted internally.
4. If test light is off after disconnecting PCM, ensure circuit No. 473 is not shorted to battery voltage. If circuit is not shorted to battery voltage, PCM is shorted internally.

Scheme 11

CHART C-12C - COOLING FAN NO LEFT SIDE FAN (3 OF 4) 3.8L - VIN L

Note. Test numbers refer to numbers on diagnostic charts. (Scheme 12)

1. Checks for battery voltage at relay harness connector terminals B4 and B6.
2. Jumpering relay terminals B6 and C4 by-passes relay, which should cause fans to run if fan motors and wiring are okay.
3. Select Tech 1 miscellaneous tests, FAN 1. Turn fans on. PCM should ground circuit No. 335. At this point, test light should be on if PCM is good and circuit No. 335 is not open.
4. Checks for battery voltage and ground to fan motor. Test light on at this point indicates a faulty fan motor connection or motor.

Scheme 12

CHART C-12D - COOLING FAN NO RIGHT SIDE FAN (4 OF 4) 3.8L - VIN L

Note. Test numbers refer to numbers on diagnostic charts. (Scheme 13)

1. Checks for battery voltage at relay harness connector terminals B8 and B10.
2. Jumpering relay harness terminals B10 and C8 by-passes right fan relay (fan No. 2). If fan runs, fan relay is faulty.
3. Checks circuit No. 473 back to PCM. If circuit No. 473 is okay, right fan relay (fan No. 2) is faulty.
4. Checks wiring to fan No. 2 motor. If okay, problem is poor connection, open ground circuit or faulty fan No. 2 motor.

Scheme 13

An intermittent may be caused by a poor connection, rubbed-through wire insulation or a wire broken inside the wire insulation. Check PCM harness connector for backed-out terminals. Connect a DVOM between affected terminal and ground. Wiggle related wires and connectors while watching DVOM for a voltage reading change. Ensure ECT sensor is not mis-scaled. See Diagnostic Trouble Code (DTC) P0117 chart in the G-TESTS W/CODES article in the ENGINE PERFORMANCE section. Ensure engine cooling system functions properly.

Cooling Fan Circuit Wiring Diagram. Scheme 14

See also:
• A/C COMPRESSOR CLUTCH CONTROLS
• COOLING FAN CHART INDEX