Engine Cooling Fan Buick Riviera VII

APPLICATION

ELECTRIC COOLING FAN APPLICATIONS

Note. This article contains test charts that are part of General Motors Computerized Engine Controls. Only those charts required to test electric cooling fans are included. Other diagnostic codes may appear while performing electric cooling fan diagnosis. For complete information on General Motors Computerized Engine Control systems see COMPUTERIZED ENGINE CONTROL section.

DESCRIPTION

All FWD, and some RWD vehicles use an electric cooling fan. This fan is used for engine and A/C condenser cooling and operates when A/C is on and if engine overheats.

OPERATION

All electric cooling fans operate when engine coolant temperature exceeds a certain value. The ECM completes ground path for the cooling fan relay. Relay contacts then close and complete circuit between fusible link and fan motor. When the engine cools, the switch opens and fan stops. If coolant sensor fails, the ECM will command constant fan operation.

A/C equipped vehicles have a separate signal line to the ECM for fan control. When A/C control switch is "ON", and A/C system low pressure switch is closed, the ECM receives a signal on this line and turns on the cooling fan. The compressor clutch does not have to engage for ECM to turn fan on.

On some models, when engine is off, ECM may turn on the fan relay and run fan for up to 7 minutes. This occurs if hot conditions were present while engine was running. Hot conditions are based on Manifold Absolute Temperature (MAT) signal to ECM, coolant temperature and time from start.

CHART C-12A, COOLING FAN CHECK FUNCTIONAL CHECK 3.8L - VIN C

All applications use 2 cooling fans and 3 relays.

The ECM energizes the low speed relay when coolant temperature exceeds 214°F (101°C). The low speed relay will also be energized when requested by the BCM based on A/C high side temperature, BCM data BD27, which exceeds 149°F (65°C).

The ECM will energize both high speed relays when coolant temperature exceeds 226°F (108°C), or when requested by BCM based on A/C high side temperature, BCM data BD27, which exceeds 149°F (65°C).

Note. Test numbers refer to test numbers on diagnostic charts.

Scheme 1

1. Codes EO14 or EO15 could mean coolant system or sensor operation is not normal. Cooling fan operation CANNOT be checked accurately.
2. ECM output EO09 grounds low speed relay through the ECM for 3 seconds on and 3 seconds off. Low speed fan should be on for 3 seconds, and off for 3 seconds.
3. ECM output EO10 grounds high speed relay through the ECM for 3 seconds on and 3 seconds off. High speed fan should be on for 3 seconds, and off for 3 seconds. (Scheme 1): Cooling Fan Check Functional Check 3.8L - VIN C

CHART C-12B, COOLING FAN CHECK NO LOW SPEED COOLING FAN 3.8L - VIN C

Note. Test numbers refer to test numbers on diagnostic charts.

Scheme 2

1. Test light should be on because harness terminal No. 2 has battery voltage with ignition on. Terminal No. 4 has battery voltage at all times.
2. Test light should be on for 3 seconds, then off for 3 seconds as EO09 cycles fan on and off.
3. Jumpering harness terminals No. 1 and 4 by-passes relay. If cooling fan runs, relay is faulty.
4. Cycling off the test light proves circuits No. 532 and 804 are okay. (Scheme 2): Cooling Fan Check No Low Speed Cooling Fan 3.8L - VIN C

CHART C-12C-1, COOLING FAN CHECK NO HIGH SPEED REAR FAN 3.8L - VIN C

Note. Test numbers refer to test numbers on diagnostic charts.

Scheme 3

1. Test light should be on because harness terminal No. 5 has battery voltage with ignition on. Terminal No. 1 has battery voltage at all times.
2. Test light should be on for 3 seconds and off for 3 seconds as EO10 cycles cooling fan.
3. Jumpering harness terminals No. 1 and 4 by-passes relay. If cooling fan runs, relay is faulty.
4. Cycling of test light proves circuits No. 533 and 804 are okay. (Scheme 3): Cooling Fan Check No High Speed Rear Fan 3.8L - VIN C

CHART C-12C-2, COOLING FAN CHECK NO HIGH SPEED FRONT FAN 3.8L - VIN C

Note. Test numbers refer to test numbers on diagnostic charts.

Scheme 4

1. Test light should be on because harness terminal No. 5 has battery voltage when ignition is on. Terminal No. 1 has battery voltage at all times.
2. Test light should be on for 3 seconds and off for 3 seconds as EO10 cycles cooling fan.
3. Jumpering harness terminals No. 1 and 4 by-passes relay. If cooling fan runs, relay is faulty.
4. Cycling of test light proves circuits No. 533 and 804 are okay. (Scheme 4): Cooling Fan Check No High Speed Front Fan 3.8L - VIN C

CHART C-12D, COOLING FAN CHECK COOLING FAN(S) ON AT ALL TIMES 3.8L - VIN C

Note. Test numbers refer to test numbers on diagnostic charts.

1. Checks to see if circuits No. 535 or 536 is shorted to ground which would cause fan relay(s) to be energized at all times.
2. High temperature will cause A/C high side temperature to exceed 122°F (50°C), and BCM will request low speed fans at all times.
3. Cooling fans will come on when engine is started, but should go off when A/C system stabilizes. Cooling fans should be off when A/C high side temperature switch is disconnected and coolant temperature is below 208°F (98°C).

Diagnostic Aids

Cooling fan should be off if coolant temperature is below 208°F (98°C) and A/C high side temperature is below 122°F (50°C).

Note. On-board diagnostics may assist in diagnosing BD21 coolant temperature sensor, and BD27 A/C high side temperature sensor.

Disconnecting the A/C high side temperature sensor should result in a BD27 reading less than -30°F (-34°C). If not, see B111 flow-chart at end of this article.

BD27 should read about 122°F (50°C) when A/C system high side pressure is approximately 160 psi (11 kg/cm 2 ).

Cooling Fan Check Cooling Fan(s) On At All Times 3.8L - VIN C. Scheme 5

CODE B111, A/C HIGH SIDE TEMPERATURE SENSOR CIRCUIT CHECK 3.8L - VIN C

The A/C high side temperature sensor is a thermistor that senses A/C refrigerant temperature at condenser outlet. The BCM applies voltage to circuit No. 732 to sensor. The sensor has high resistance when cold, and less resistance as sensor warms. Voltage feedback to BCM will vary from 5 volts to 0 volt, informing BCM of refrigerant temperature.

Code B111 will set if ignition is on, outside temperature sensor has not failed and reads above 32°F (0°C), and signal voltage reads less than -30°F (-34°C) or over 363°F (184°C). During the time the failure is present, a substitute temperature will be implemented to allow continued use of the climate control system. The engine cooling fans will be operated on high speed when A/C compressor clutch is engaged.

Note. Test numbers refer to test numbers on diagnostic charts.

1. This step checks to see if open circuit reading is due to the circuit or sensor. If the open circuit changes to a shorted circuit reading after jumpering the sensor terminals, the BCM and wiring are okay.
2. By applying a ground to various points in the circuit, an open can be isolated by observing the parameter display. When an open is found, the reading will NOT change from open to shorted.
3. This step checks to see if shorted reading is due to the circuit or sensor. If the shorted circuit reading changes to an open circuit when sensor is disconnected, BCM and wiring are okay.

Note On Intermittents

If Code B111 is set with Code B112, check for an intermittent open in circuit No. 736 between splice S2 and S3.

If an intermittent Code B111 is being set, check the B111 snap data value for high side temperature, BD27. If the BD27 value is under -30°F (-34°C), the code was caused by an open in circuits No. 732, 736 or high side temperature sensor. If the BD27 value is over 363°F (184°C), the code was caused by a short to ground on circuit No. 732 or a shorted A/C high side temperature sensor. Wiggle related wires while observing BCM data BD27. If a failure is induced, the reading will change.

If the BCM BD27 value displayed is not reasonably close to the high side gauge pressure reading, check for poor terminal contacts or replace sensor.

A/C High Side Temperature Sensor Circuit Check 3.8L - VIN C. Scheme 6

C0DE B441, COOLING FAN PROBLEMS 4.5L - VIN 5

Code B441 is set by the BCM if it receives an improper cooling fans feedback signal. The cooling fans control module is designed to change feedback voltage on circuit No. 791 as follows

1. 7 volts if the fan has been turned off.
2. 0 volt if the fans have been turned on.
3. 7 volts if the fans have been turned on and an excessive current draw exists (stalled or shorted fan motor.
4. 0 volt if both fan connections are open.

The BCM will set Code B441 if either of the following conditions exist

1. The BCM has commanded the fans off but the feedback voltage remains low. The BCM will keep Code B441 current for the rest of the ignition cycle and continue providing a normal control signal to the cooling fans control module. The BCM will again test this condition on the next ignition cycle to determine if a fault is intermittent. The "COOLANT TEMP/FAN" will be displayed on the instrument cluster when cooling fan operation is required.
2. The BCM has commanded the fans on but the feedback voltage remains high. The BCM will command the fans off to protect the system from a possible stalled or shorted fan motor. If the control temperatures (coolant and A/C high side) should drop below the fan turn off points and later require the fans on, the BCM will repeat the test to determine if the fault is intermittent. The "COOLANT TEMP/FAN" will be displayed on the CCDIC when cooling fan operation is required. NOTE: Test numbers refer to test numbers on diagnostic charts.

1. The cooling fans override feature (BS04) can be used to evaluate the system operation. If high speed fans are off when "HIGH FANS" are commanded, or if either fan is on when "FANS OFF" is commanded, this diagnostic path will isolate fault.
2. The cooling fans feedback input B141 can be used to evaluate the feedback signal being received by the BCM. If the input does NOT agree with the actual fans operation, circuit No. 791 should be checked for fault. If the input does agree with the commanded fans operation within the appropriate time period, the cause of Code B441 does NOT currently exist.

If an intermittent Code B441 is being set, wiggle the related wiring while observing the test data. If a failure is induced, the fan status data will not agree with the commanded operation. This will help isolate the fault.

Cooling Fan Problems 4.5L - VIN 5. Scheme 7

Trouble Shooting Hints

Try the following checks performing System Check

1. If coolant fans do not operate, check fuse No. 6 and fusible link "D".
2. If only one coolant fan does not operate, check the electrical wires to that coolant fan. If the wiring is okay, replace coolant fan.
3. If coolant fan only operates in high speed, check the WHT (962) wire from the coolant fan resistor. If the wire is good, replace coolant fans resistor.

System Check

Use System Check Table as a guide to normal operation. Refer to System Diagnosis for a list of symptoms and diagnostic steps.

System Diagnosis

1. Do the tests listed for your Symptom Table below.
2. Tests follow the Symptom Table.

Symptom Table. Scheme 8

A: Low Speed Relay Test (Table 1). Scheme 9

A: Low Speed Relay Test (Table 2). Scheme 10

A: Low Speed Relay Test (Table 3). Scheme 11

B: Medium Speed Relay Test (Table 1). Scheme 12

B: Medium Speed Relay Test (Table 2). Scheme 13

B: Medium Speed Relay Test (Table 3). Scheme 14

C: High Speed Relay Test (Table 1). Scheme 15

C: High Speed Relay Test (Table 2). Scheme 16

C: High Speed Relay Test (Table 3). Scheme 17

C: High Speed Relay Test (Table 4). Scheme 18

C: High Speed Relay Test (Table 5). Scheme 19

D: Continuous High Speed Operation Test (Table 1 & 2). Scheme 20

Electric Cooling Fan - "E" Body. Scheme 21

Single Relay Electric Cooling Fan (Eldorado). Scheme 22