DESCRIPTION & OPERATION
| WARNING | To avoid the danger of being burned, do not remove the coolant recovery reservoir cap while the engine and radiator is still hot. Scalding fluid and steam may be blown out under pressure. Check the engine coolant level visually in the "see-through"reservoir. The level should be at or above the "FULL COLD" mark on the tank when the engine is cold. At normal operating temperatures the engine coolant level should be above the "FULL COLD" mark on the tank. |
| WARNING | Vehicles are equipped with air bag supplemental restraint system. Before attempting any repairs involving steering column, instrument panel or related components, see SERVICE PRECAUTIONS and DISABLING & ACTIVATING AIR BAG SYSTEM in appropriate AIR BAG RESTRAINT SYSTEMS article. |
| CAUTION | When battery is disconnected, vehicle computer and memory systems may lose memory data. Driveability problems may exist until computer systems have completed a relearn cycle. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION before disconnecting battery. |
The cooling system utilizes 2 plastic fans. The fans are driven by individual electric motors which are controlled electrically by the Powertrain Control Module (PCM). Fan speed is variable and is controlled based on engine coolant and A/C high-pressure refrigerant temperature.
CIRCUIT OPERATION
Powertrain Control Module (PCM) controls both cooling fans by controlling 3 relays through 2 outputs. There are 2 modes of cooling fan operation, low and high speed. In the low speed mode, the cooling fans are powered in series. the PCM energizes cooling fan 1 relay, causing both cooling fans to run at low speed. In the high speed mode, the cooling fans are powered in parallel which runs the fans at high speed. The PCM energizes all 3 cooling fan relays during high speed mode.
LOW SPEED CONDITIONS
The PCM turns on the cooling fans at low speed when the engine coolant temperature exceeds 223°F (106°C). The cooling fans turn off when the engine coolant temperature falls below 216°F (102°C). The PCM monitors engine coolant temperature using the engine coolant temperature sensor input on Yellow wire (410).
The PCM also activates low speed operation if the transaxle temperature sensor reads above 239°F (115°C). The cooling fans turn off when the transaxle temperature falls below 230°F (110°C). The PCM monitors transaxle temperature using the transaxle sensor input on Yellow/Black wire (1227).
The heater and A/C programmer requests the PCM to turn on the cooling fans at low speed through the class II data line when the A/C high side refrigerant temperature exceeds 122°F (50°C). The programmer requests the cooling fans turn off once the A/C high side refrigerant temperature falls below 117°F (47°C).
The PCM turns the cooling fans ON at low speed if a low coolant level is detected and the engine coolant temperature exceeds 176°F (80°C). The cooling fans turn off when the engine coolant temperature drops below 169°F (76°C).
LOW SPEED OPERATION
Low speed cooling fan operation occurs when the PCM grounds the cooling fan relay 1 relay coil on CKT 335. With only cooling fan relay 1 energized, voltage is applied to both the left and right cooling fan motors. Power is supplied to the motors through the cooling fan 1 relay contract circuits, Black wire (532), White wire (504) and the Light Blue wire (409), and the cooling fan 2 relay contracts.
The 2 motors are connected through a series circuit. This circuit divides the voltage applied by the COOL FNS Maxi(R) Fuse between the 2 motors. The division of the voltage causes the motors to operate at a lower speed. In the series mode, the fans are grounded through Black wire (350) and ground G107.
HIGH SPEED CONDITIONS
The PCM turns the cooling fans at high speed when the engine coolant temperature exceeds 230°F (110°C) or the Engine Coolant Temperature (ECT) sensor circuit has failed. The PCM switches the cooling fans to low speed operation if the engine coolant temperature falls below 221°F (105°C).
The PCM also activates high speed operation if the transaxle temperature exceeds 248°F (120°C). The PCM switches to low speed operation once the transaxle temperature falls below 239°F (115°C).
The PCM turns the cooling fans on at high speed if a low coolant level is detected and engine coolant temperature exceeds 185°F (85°C). The PCM switches to low speed operation once the engine coolant temperature drops below 176°F (80°C).
The heater and A/C programmer requests the PCM to turn the cooling fans at high speed through the class II data line if the A/C high side refrigerant temperature exceeds 147°F (64°C). The heater and A/C programmer requests that the cooling fans switch to low speed operation when the A/C high side refrigerant temperature falls below 124°F (51°C).
HIGH SPEED OPERATION
The cooling fan runs at high speed when the PCM grounds cooling fan 1, 2 and 3 relays on circuits, Dark Green wire (335) and Dark Blue wire (473). With both cooling fan 1 and 2 relays energized, battery voltage is applied to the left cooling fan motor through the relay contacts. The left cooling fan motor runs at high speed because the fan motor is grounded directly through White wire (504); the contacts of cooling fan 2 relay, Black wire (350) and ground G107.
Since cooling fan 3 relay is also energized during high speed operation, battery voltage is applied directly to the right cooling fan motor through the closed contacts of the relay. The fan runs at high speed since it is no longer in series with the left cooling fan motor.
ENGINE COOLANT TEMPERATURE SENSOR
The Engine Coolant Temperature (ECT) sensor is a thermistor (a resistor which changes value based on temperature) mounted in the engine coolant stream. See ENGINE COOLANT TEMPERATURE (ECT) SENSOR under COMPONENT TESTS. Low coolant temperature produces a high resistance (100 k/ohms at -40°F/-40°C), while high temperature causes low resistance (70 ohms at 266°F/130°C).
The PCM supplies a 5 volt signal to the ECT sensor through a resistor in the PCM and monitors the terminal voltage. Since this forms a series circuit to ground through the ECT sensor, high sensor resistance (low temperature) will result in high PCM terminal voltage. When the ECT sensors resistance is low (high temperature), the terminal voltage will be drawn lower. This terminal voltage indicates engine coolant temperature to the PCM.
A hard fault in the ECT sensor should set either a DTC P0117 or P0118. An intermittent failure in the ECT sensor circuit should set either a DTC P1114 or P1115. For diagnostic procedures, see TESTS W/CODES article in ENGINE PERFORMANCE.
COMPONENT LOCATIONS
| Component | Location |
|---|---|
| Cooling Fan 1 Relay | At Rear Of Radiator, Center Bottom, Between Cooling Fans. (Scheme 1) |
| Cooling Fan 2 Relay | At Rear Of Radiator, Center Bottom Between Cooling Fans. (Scheme 1) |
| Cooling Fan 3 Relay | At Rear Of Radiator, Center Bottom Between Cooling Fans. (Scheme 1) |
| Left Cooling Fan Motor | Behind Left Side Of Radiator. (Scheme 1) |
| Right Cooling Fan Motor | Behind Right Side Of Radiator. (Scheme 1) |
| Engine Compartment Fuse/Relay Center | Forward Of Left Front Strut Tower. (Scheme 2) |
| Engine Coolant Temperature Sensor | At Left Rear Corner Of Engine, Near Base Of Engine Lift Hook. (Scheme 3) |
| Heater & A/C Programmer | Behind Right Side Of Instrument Panel, Near Rear Of Instrument Panel Compartment. (Scheme 4) |
| Powertrain Control Module (PCM) | In Left Front Corner Of Engine Compartment, Under Air Filter Housing. (Scheme 5) |
| Right Maxi(R) Fuse Block | Forward Of Left Front Strut Tower, Near engine Compartment Fuse/Relay Center. (Scheme 2) |
| G107 | At Lower Left Front Of Engine, Below Thermostat Housing. (Scheme 6) |
| S117 | In Engine Harness, Approximately 34 cm From Right Engine Cooling Fan Connector. (Scheme 1) |
| S118 | In Engine Harness Approximately 16.5 cm From PCM Connector Breakout. (Scheme 6) |
| S129 | In engine Harness Approximately 4 cm from C129 Connector Breakout. (Scheme 1) |
| S130 | In Engine Harness, Approximately 6.5 cm From Electronic Brake Traction Control Module (EBTCM) Connector Breakout. (Scheme 1) |
COMPONENT LOCATIONS
Scheme 1
Scheme 2
Scheme 3
Scheme 4
Scheme 5
Scheme 6
SYSTEM OPERATION CHECK
Note. Test step(s) below refer to number(s) on electric engine cooling fan diagnosis (functional check). (Scheme 7) For test tables relating to the functional check (Scheme 8)- (Scheme 12).
Circuit Description
Note. If the cooling fans operate when commanded OFF and DTC P1660 is not set, a cooling fan relay is stuck on or a cooling fan circuit is shorted to power.
To determine if a fault is present, perform the system operation check. See SYSTEM OPERATION CHECK . If DTC P1660 is set, or sets during the system operation check, it must be diagnosed before proceeding with any of the symptom tests. See DTC P1660: COOLING FAN CONTROL CIRCUITS under DIAGNOSTIC TESTS.
When the PCM commands low speed fan operation, it grounds the cooling fan relay 1 which allows current to flow through both cooling fans in a series circuit to ground. If the PCM commands high speed fan operation it grounds all the cooling fan relays, including fan relay 1, which changes the circuit to a parallel circuit to ground. If a fault occurs certain symptoms will occur due to the series/parallel circuit design.
Low Speed Fan Operation
The PCM will command low speed fan operation when the engine coolant temperature exceeds 229°F (106°C), transmission fluid temperature exceeds 302°F (150°C), A/C operation is requested or after the vehicle is shut off and the coolant temperature is above 304°F (151°C) and system voltage is 12-volts or more. The fans will run for approximately 3 minutes. The fans will turn off automatically if the coolant temperature drops below 216°F (102°C). If any repairs are performed, repeat the system operation check. See SYSTEM OPERATION CHECK . This will help diagnose possible multiple failures, for example 2 water contaminated relays.
High Speed Fan Operation
The PCM will command high speed fan operation when the engine coolant temperature reaches 234°F (112°C), transmission temperature is more than 304°F (151°C) or when certain DTC set. The fans will switch from high to low speed (except when certain DTCs are set) when the coolant drops below 229°F (106°C). If any repairs are performed, repeat the system operation check. See SYSTEM OPERATION CHECK . This will help diagnose possible multiple failures, for example 2 water contaminated relays.
Diagnostic Aids
A DTC that has been cleared will not reset if the conditions that were present when the DTC set, no longer exist. Sometimes with the help of a snapshot on DTC set data or information from the driver, the problem may still be identified or at least narrowed down to a short list of possible intermittent failures. This may explain what to look for and which direction to head in looking for an intermittent failure.
Test Step No. 1
Perform the ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See BASIC DIAGNOSTIC PROCEDURES article in ENGINE PERFORMANCE. System check must be performed first so that any mis-diagnosis is avoided, due to the PCM commanding the fans on due to a present DTC, etc. (Scheme 7)
Test Step No. 2
Test step is checking to see if there is a fault on the cooling fan relay control circuits. (Scheme 7)
Test Step No. 3
Test step checks if any A/C DTCs will set. If A/C DTCs set they must be diagnosed before proceeding with the system operation check. If any DTCs are set, go to appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING or TESTS W/CODES article in ENGINE PERFORMANCE.
Test Step No. 4
Test step commands fans on in sequence to determine the symptom (fault-if any) is present. (Scheme 7)
Scheme 7
Scheme 8
Scheme 9
Scheme 10
Scheme 11
Scheme 12
SELF-DIAGNOSTIC SYSTEM
Note. Use of Tech 1 scan tool is required to retrieve DTCs. Refer to user reference manuals supplied with scan tool.
RETRIEVING DIAGNOSTIC TROUBLE CODES
Note. Before connecting scan tool to vehicle, diagnostic system should be checked to determine if system is operating properly and if information received will be accurate. This is done by performing the ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See BASIC DIAGNOSTIC PROCEDURES article in ENGINE PERFORMANCE. If vehicle does not pass OBD system check, information received may be invalid.
CLEARING DIAGNOSTIC TROUBLE CODES
To clear DTCs from memory, either to determine if malfunction will occur again or after making necessary repairs, disconnect power supply to PCM/VCM for at least 30 seconds or clear codes using a scan tool.
DIAGNOSTIC TROUBLE CODE DEFINITIONS
| DTC (1) | Description |
|---|---|
| P1660 | Cooling Fan Control Circuits |
| (1) Perform appropriate test under DIAGNOSTIC TESTS . Codes listed in this table are only for testing covered in this article. For a complete list of codes, see TESTS W/CODES in ENGINE PERFORMANCE. | |
| (1) | Perform appropriate test under DIAGNOSTIC TESTS . Codes listed in this table are only for testing covered in this article. For a complete list of codes, see TESTS W/CODES in ENGINE PERFORMANCE. |
DIAGNOSTIC TROUBLE CODE DEFINITIONS
PCM Quad Driver Module provides 4 searchable ground outputs for operating solenoids, relays, warning lights, and other devices. Each of these ground outputs has an internal fault line that feed back to the PCM. When the output is off, the quad driver should receive 12 volts fed to the solenoids, relays, etc. When the output is on, it should receive zero volts, since it is grounding the output. If it receives zero volts when the output is off or 12 volts when the output is on, it sets the fault line low. DTC is used to monitor the fault line of the cooling fan control relay output.
Diagnostic Procedures
- Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See «BASIC DIAGNOSTIC PROCEDURES»(/cadillac/deville-concours/1994-1998/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article in ENGINE PERFORMANCE. After system check is completed, go to next step.
- Turn ignition on. Turn A/C controls OFF. Using scan tool in MISC TESTS, select OUTPUT TESTS, then select FAN RELAYS. Note QUAD DRIVER 1 display and command ALL RELAYS OFF. If scan tool display indicates OK, go to next step. If scan tool display does not indicate OK, go to step 8.
- In MISC TESTS, select OUTPUT TESTS, then select FAN RELAYS (QUAD DRIVER 1 display and ALL RELAYS ON). If scan tool display indicates OK, go to next step. If scan tool display does not indicate OK, go to step 5.
- If cooling fan is inoperative or if a fault is suspected, diagnose cooling fan. See «SYSTEM OPERATION CHECK»(/cadillac/deville-concours/1994-1998/remont/cooling-fan/#engine-cooling-fan__system-operation-check) under TROUBLESHOOTING. If cooling fan operates, fault is not present at this time. See «DIAGNOSTIC AIDS»(/cadillac/deville-concours/1994-1998/remont/cooling-fan/#engine-cooling-fan__diagnostic-aids) in SYSTEM OPERATION CHECK under TROUBLESHOOTING.
- While noting QUAD DRIVER 1 display, command FAN RELAY 1 ON. If scan tool display indicates OK, go to step 7. If scan tool display does not indicate OK, go to next step.
- Store fluid life index as indicated on scan tool. Turn ignition to LOCK position and wait 30 seconds, then disconnect PCM harness connector C2. (Scheme 13) Remove fan relay 1 (low speed). Using DVOM, check voltage between ground and cooling fan low speed control circuit at PCM harness connector terminal. If voltage reading is.5 volt or less, go to step 18. If voltage reading is greater than.5 volt, go to step 16.
- Store fluid life index as indicated on scan tool. Turn ignition to LOCK position and wait 30 seconds, then disconnect PCM harness connector C2. Remove fan relays 2 and 3. See «COMPONENT LOCATIONS»(/cadillac/deville-concours/1994-1998/remont/cooling-fan/#engine-cooling-fan__component-locations). Using DVOM, check voltage between ground and cooling fan high speed control circuit at PCM harness connector terminal. If voltage reading is.5 volt or less, go to step 18. If voltage reading is more than.5 volt, go to step 17.
- With ALL RELAYS still commanded OFF, observe operation of both cooling fans. If either fan is operating, go to next step. If neither fan is operating, go to step 10.
- Store fluid life index as indicated on scan tool. Turn ignition to LOCK position and wait 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Using DVOM, check voltage between ground and cooling fan low speed control circuit at PCM harness connector terminal. If voltage reading is less than 10 volts, go to step 15. If voltage reading is 10 volts or greater, go to step 14.
- Store fluid life index as indicated on scan tool. Turn ignition to LOCK position and wait 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Using DVOM, check voltage between ground and cooling fan high and low speed control circuits at PCM harness connector terminal. If voltage reading is 10 volts or greater, go to step 18. If voltage reading is less than 10 volts, go to next step.
- If voltage reading from step 9 is low for both terminals, go to step 13. If voltage reading from step 9 is low only in one of the terminals, go to next step.
- Repair open in circuit or replace fan relay for the circuit that measured low. (Scheme 13)
- Repair cause of no voltage to both circuits. Replace fuse if blown.
- Repair short to ground in cooling fan high speed control circuit.
- Repair short to ground in cooling fan low speed control circuit.
- Repair short to voltage in cooling fan low speed control circuit.
- Repair short to voltage in cooling fan high speed control circuit.
- Check terminal contact at PCM. Repair as necessary. If terminal contact is okay, go to next step.
- Replace PCM. See POWERTRAIN CONTROL MODULE (PCM) under IGNITION SYSTEM in «REMOVAL & INSTALLATION»(ref-20434) article in ENGINE PERFORMANCE.
DTC P1660 Test. Scheme 13
ENGINE COOLANT TEMPERATURE (ECT) SENSOR
If a coolant sensor-related diagnostic trouble code is present, see TESTS W/CODES article in ENGINE PERFORMANCE. See ECT DIAGNOSTIC TROUBLE CODE DEFINITIONS table. An out-of-calibration sensor may not set a diagnostic trouble code. To test sensor calibration, disconnect ECT sensor connector. Measure resistance between sensor terminals. Resistance should be high when engine is cold and drop as engine warms. See ECT SENSOR RESISTANCE VALUES table.
| DTC (1) | Description |
|---|---|
| P0116 | Excessive Change In Sensor Output Voltage |
| P0117 | Circuit Low |
| P0118 | Circuit High |
| P0125 | Excessive Time To Closed Loop |
| P1114 | Circuit Intermittent Low |
| P1115 | Circuit Intermittent High |
| (1) See TESTS W/CODES article in ENGINE PERFORMANCE for testing procedures. | |
| (1) | See TESTS W/CODES article in ENGINE PERFORMANCE for testing procedures. |
ECT DIAGNOSTIC TROUBLE CODE DEFINITIONS
| °F (°C) | (1) Ohms |
|---|---|
| 212 (100) | 177 |
| 194 (90) | 241 |
| 158 (70) | 467 |
| 104 (40) | 1459 |
| 68 (20) | 3520 |
| 23 (-5) | 12,300 |
| 14 (-10) | 16,180 |
| 0 (-18) | 25,000 |
| 4 (-20) | 28,680 |
| 22 (-30) | 52,700 |
| 40 (-40) | 100,700 |
| (1) Measure resistance across sensor terminals. | |
| (1) | Measure resistance across sensor terminals. |
ECT SENSOR RESISTANCE VALUES
COOLING FAN RELAY OPERATION
To check relay operation, see COOLING FAN RELAY OPERATION TEST table.
| Operational Mode | OFF | LOW FANS | HIGH FANS |
|---|---|---|---|
| Low Speed Cooling Fan Relay (#1) | De-Energized | Energized | Energized |
| Series/Parallel Cooling Fan Relay #2 (1) | De-Energized | De-Energized | Energized |
| High Speed Cooling Fan Relay #3 | De-Energized | De-Energized | Energized |
| (1) The series/parallel cooling fan relay is a dual position switch and while de-energized, supplied a ground path for the low speed fan circuit. | |||
| (1) | The series/parallel cooling fan relay is a dual position switch and while de-energized, supplied a ground path for the low speed fan circuit. |
COOLING FAN RELAY OPERATION TEST
REMOVAL & INSTALLATION
| WARNING | Vehicles are equipped with air bag supplemental restraint system. Before attempting any repairs involving steering column, instrument panel or related components, see SERVICE PRECAUTIONS and DISABLING & ACTIVATING AIR BAG SYSTEM in appropriate AIR BAG RESTRAINT SYSTEMS article. |
| CAUTION | When battery is disconnected, vehicle computer and memory systems may lose memory data. Driveability problems may exist until computer systems have completed a relearn cycle. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION before disconnecting battery. |
ENGINE COOLANT FAN
| WARNING | Keep hands, tools and clothing away from engine coolant fan to help prevent personal injury. This engine coolant fan is electric and can come on weather or not the engine is running. The engine coolant fan can start automatically in response to a temperature sensor with the ignition in the on position. |
Removal
- Remove headlamp cover panel.
- Remove engine air filter assembly.
- Remove left engine support torque strut.
- Relocate upper radiator hose out of the way.
- Remove upper transmission oil cooler line.
- Remove electric cooling fan wiring connectors. (Scheme 1)
- Remove 4 cooling fan retaining bolts and remove electric cooling fan. (Scheme 14)
Scheme 14
Installation
- Place cooling fans on vehicle and secure with 4 bolts. Torque bolts to 89 INCH lbs (10 N.m). (Scheme 14)
- Install electrical connectors. (Scheme 1)
- Install upper transmission oil cooler line.
- Reposition radiator hose.
- Replace left engine torque strut.
- Replace engine air filter assembly.
- Replace headlamp cover panel.
| WARNING | Allow sufficient time for the engine to cool before removing the ECT sensor. Personal injury or excessive coolant loss may result if the engine is hot. |
| CAUTION | Use care when handling the coolant sensor. Damage to the coolant sensor will effect the operation of the fuel control system. |
Note. A non-hardening sealer should be applied to the sensor threads prior to installation to prevent coolant leaks. Use P/N 1050805 or equivalent.
- Partially drain the cooling system.
- Disconnect the ECT sensor electrical connector.
- Unscrew and remove the ECT sensor. (Scheme 15)
Scheme 15
- Install the ECT sensor and tighten to 15 ft. lbs. (20 N.m). (Scheme 15)
- Connect the ECT sensor electrical connector.
- Refill cooling system.
TORQUE SPECIFICATIONS
| Application | Ft Lbs. (N.m) |
|---|---|
| Engine Coolant Temperature Sensor | 15 (20) |
| INCH Lbs. (N.m) | |
| Electric Cooling Fan Mounting Bolts/Screws | 89 (10) |
TORQUE SPECIFICATIONS
