Engine Cooling Fan — Chevrolet Suburban IX (1991-2001)

DESCRIPTION

All FWD and some RWD vehicles use an electric cooling fan. 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. One or more cooling fan relays may be used. (Scheme 1)

TROUBLE SHOOTING

Note. This article contains only that text required to test electric cooling fans. Other diagnostic information may be referenced while performing electric cooling fan diagnosis. See appropriate ENGINE PERFORMANCE articles for complete information on General Motors Computerized Engine Control systems.

Note. Some RWD trucks and vans are equipped with an auxiliary electric cooling fan. The auxiliary electric cooling fan is not controlled by Powertrain Control Module (PCM).

Trouble shoot cooling fan using appropriate diagnostic information provided. For cooling fan relay location, see COOLING FAN RELAY LOCATION table.

Application	Location
"C" & "K" Series	In Engine Compartment Fuse/Relay Block, Near Master Cylinder
"U" Series	(1) Behind Right Headlight, Near Fuel Evaporative Canister
(1) (Scheme 1)

(1)	(Scheme 1)

COOLING FAN RELAY LOCATION

Scheme 1

SCAN TOOL

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 Tool (TK O-A) and Cartridge Kit (7000001), Tech 1 OBD II Vehicle Interface Module Kit (7000041), or other scan for interpretation. Several scan tools are available for diagnostic work. Refer to scan tool manufacturer's instructions.

WARNING

Vehicles may be equipped with a PCM using an Electronically Erasable Programmable Read Only Memory (EEPROM). When replacing PCM, the new PCM must be programmed.

Power is supplied to cooling fan motors through fusible links. Relays are energized when PCM completes ground path to relay coil. During fan No. 1 operation, PCM supplies a ground path for fan No. 1 relay through ODM "B" output No. 1. This closes fan No. 1 relay contacts and current flows from battery through relay and to puller cooling fan. Puller cooling fan is grounded at engine block.

PCM commands fan No. 1 on when engine coolant temperature increases to 226°F (108°C). Fan No. 1 will remain on until engine coolant temperature decreases to less than 271°F (133°C). PCM also commands fan No. 1 on when A/C refrigerant pressure increases to greater than 190 psi (13.4 kg/cm 2 ). Fan No. 1 will remain on until A/C refrigerant pressure decreases to less than 117 psi (8.2 kg/cm 2 ).

During fan No. 2 operation, PCM keeps fan No. 1 energized and supplies a ground path for fan No. 2 relay through ODM "B" output No. 2. This closes fan No. 2 relay contacts and current flows to pusher cooling fan. Pusher cooling fan is grounded at chassis. PCM commands fan No. 2 on when engine coolant temperature increases to 232°F (111°C). Fan No. 2 will remain on until engine coolant temperature decreases to 226°F (108°C). PCM also commands fan No. 2 on when vehicle speed is less than 48 MPH. and A/C refrigerant pressure increases to greater than 240 psi (16.9 kg/cm 2 ). Fan No. 2 will remain on until A/C refrigerant pressure decreases to 190 psi (13.4 kg/cm 2 ).

Cooling Fan Circuit Diagnosis

If On-Board Diagnostic (OBD) system check has not been performed, see appropriate ENGINE PERFORMANCE article. If OBD system check has been performed, go to next step.
If any Diagnostic Trouble Codes (DTCs) are stored, perform testing for codes first. If no DTCs are present, go to next step.
Ensure engine coolant temperature is less than 212°F (100°C). Turn A/C off. Turn ignition on. If both fans are off, go to next step. If both fans are on, go to step 43).
Select scan tool MISC. TESTS, RELAY CONTROL function. Command fan No. 1 on. Observe puller fan. If puller fan is running, go to next step. If puller fan is not running, go to step 6).
Select scan tool MISC. TESTS, RELAY CONTROL function. Command fan No. 2 on. Wait 6 seconds, then observe pusher fan. If pusher fan is running, problem may have been intermittent. If pusher fan is not running, go to step 19).
Disconnect fan No. 1 relay electrical connector. Turn ignition on, engine off. Connect a test light between terminals No. 85 (Red wire) and No. 86 (Dark Green wire) in fan No. 1 relay harness connector. Select scan tool MISC. TEST, RELAY CONTROL function and command fan No. 1 on. If test light illuminates, go to next step. If test light does not illuminate, go to step 15)
Check for blown Gray fusible link near starter solenoid. If link is blown, go to step 19). If link is not blown, go to next step.
Connect test light to ground and probe terminal No. 87 (Red wire) in fan No. 1 relay harness connector. If test light illuminates, go tostep 10). If test light does not illuminate, go to next step.
Locate and repair open battery feed circuit to terminal No. 87 (Red wire) in fan No. 1 relay connector. After repairs, go to step 64).
Turn ignition off. Connect a fused (20-amp) jumper wire between terminals No. 30 (Light Blue wire) and No. 87 (Red wire) in fan No. 1 relay harness connector. If puller fan is running, go to step 61). If puller fan is not running, go to next step.
Disconnect puller fan electrical connector. With fused jumper wire connected between terminals No. 30 (Light Blue wire) and No. 87 (Red wire) in fan No. 1 relay harness connector, connect test light between puller fan harness connector terminals. If test light illuminates, go to step 60). If test light does not illuminate, go to next step.
Connect test light to battery voltage and probe puller fan ground circuit at puller fan electrical connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 14).
Locate and repair open in puller fan feed circuit (Light Blue wire). After repairs, go to step 64).
Locate and repair open in puller fan ground circuit (Black wire). After repairs, go to step 64).
Connect test light to ground. Probe terminal No. 85 (Red wire) at fan No. 1 relay harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 17).
Turn ignition off. Disconnect PCM Blue harness connector. Connect test light between terminals No. 85 (Red wire) and No. 86 (Dark Green wire) at fan No. 1 relay harness connector. Jumper fan No. 1 relay driver circuit to ground at PCM connector. If test light illuminates, go to step 59). If test light does not illuminate, go to step 18).
Locate and repair open in battery feed circuit to terminal No. 85 (Red wire) in fan No. 1 relay harness connector. After repairs, go to step 64).
Locate and repair open in fan No. 1 relay driver circuit. After repairs, go to step 64).
Connect test light to battery voltage and probe terminal No. 87 (Red wire) at fan No. 1. If test light illuminates, go to next step. If test light does not illuminate, go to step 21).
Locate and repair short to ground in battery feed circuit to terminal No. 30 (Light Blue wire) in fan No. 1 relay connector. After repairs, go to step 64).
Disconnect puller fan electrical connector. Connect a test light to battery voltage and probe terminal No. 30 (Light Blue wire) at fan No. 1 relay harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 60).
Locate and repair short to ground in pusher fan feed circuit (Light Blue wire). After repairs, go to step 64).
Disconnect fan No. 2 relay electrical connector. Turn ignition on. Connect a test light between terminals No. 85 (Brown wire) and No. 86 (Dark Blue wire) in fan No. 2 relay harness connector. Select scan tool MISC. TEST relay control function and command fan No. 2 on. If test light illuminates, go to next step. If test light does not illuminate, go to step 32).
Check for a blown Gray fusible link located at remote battery stud that feeds fan No. 2 relay terminal No. 87 (Red wire). If fusible link is blown, go to step 39). If fusible link is not blown, go to next step.
Connect test light to ground and probe terminal No. 87 (Red wire) in fan No. 2 relay harness connector. If test light illuminates, go tostep 27). If test light does not illuminate, go to next step.
Locate and repair open in feed circuit to fan No. 2 relay terminal No. 87 (Red wire). After repairs, go to step 64).
Turn ignition off. Connect a 20-amp fused jumper between terminals No. 30 (Black wire) and No. 87 (Red wire) at fan No. 2 relay connector. If pusher fan is running, go to step 63). If pusher fan is not running, go to next step.
Disconnect pusher fan electrical connector. Connect a 20-amp fused jumper between terminals No. 30 (Black wire) and No. 87 (Red wire) at fan No. 2 relay connector. Connect a test light between pusher fan harness connector terminals. If test light illuminates, go tostep 62). If test light does not illuminate, go to next step.
Connect test light to battery voltage and probe ground circuit terminal (Black wire) at pusher fan connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 31).
Locate and repair open in pusher fan feed circuit (Black wire). After repairs, go to step 64).
Locate and repair open in pusher fan ground circuit (Black wire). After repairs, go to step 64).
Check IGN FUSE (15-amp) that feeds fan No. 2 relay terminal No. 85 (Brown and Pink wires). If fuse is blown, go to next step. If fuse is not blown, go to step 25).
Remove IGN FUSE (15-amp) that feeds fan No. 2 relay terminal No. 85 (Brown and Pink wires). Probe terminal No. 85 (Brown wire) at fan No. 2 relay harness connector with a test light to voltage. If test light illuminates, go to next step. If test light does not illuminate, go to step 63).
Locate and repair short to ground in feed circuit to fan No. 2 relay terminal No. 85 (Brown wire). After repairs, go to step 64).
Probe terminal No. 85 (Brown wire) in fan No. 2 relay harness connector with a test light to ground. If test light illuminates, go to next step. If test light does not illuminate, go to step 37).
Turn ignition off. Disconnect PCM harness connector. Connect test light between terminals No. 85 (Brown wire) and No. 86 (Dark Blue wire) at fan No. 2 relay harness connector. Jumper fan No. 2 relay driver circuit to ground at PCM harness connector C1, terminal No. 31 (Dark Blue/White wire). Turn ignition on. If test light is on, go tostep 59). If test light is not on, go to step 38).
Locate and repair open in feed circuit to fan No. 2 relay connector terminal No. 85 (Brown wire). After repairs, go to step 64).
Locate and repair open in fan No. 2 driver circuit. After repairs, go to step 64).
Connect test light to ground and probe terminal No. 87 (Red wire) at fan No. 2 relay harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 41).
Locate and repair short to ground in feed circuit to fan No. 2 relay connector terminal No. 87 (Red wire). After repairs, go to step 64).
Disconnect pusher fan electrical connector. Probe terminal No. 87 (Red wire) in fan No. 2 relay harness connector with a test light to ground. If test light illuminates, go to next step. If test light does not illuminate, go to step 62).
Locate and repair short to ground in pusher fan feed circuit (Red and Black wires). After repairs, go to step 64).
If both fans are running, go to next step. If both fans are not running, go to step 45).
Turn ignition off. Disconnect A/C pressure sensor. Turn ignition on. Using scan tool, monitor A/C pressure. If scan tool indicates A/C pressure at zero psi, go to step 49). If scan tool does not indicate A/C pressure at zero psi, go to step 59).
If puller fan is running, go to next step. If puller fan is not running, go to step 54).
Using scan tool, monitor A/C pressure. If scan tool indicates A/C pressure greater than 190 psi (13.3 kg/cm 2 ), go to next step. If scan tool does not indicate A/C pressure greater than 190 psi (13.3 kg/cm 2 ), go to step 48)
Disconnect A/C pressure sensor. Using scan tool, monitor A/C pressure. If A/C pressure is zero psi, go to step 53). If A/C pressure is not zero psi, go to step 59).
Disconnect fan No. 1 relay electrical connector. If puller fan is running, go to step 52). If puller fan is not running, go to next step.
Probe terminal No. 86 (Dark Green wire) in fan No. 1 relay harness connector with a test light to ground. If test light illuminates, go to next step. If test light does not illuminate, go to step 61).
Turn ignition off. Disconnect PCM harness connector. Using test light connected to ground, probe terminal No. 86 (Dark Green wire) in fan No. 1 relay harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 50).
Locate and repair short to ground in fan No. 1 relay driver circuit. After repairs, go to step 64).
Locate and repair short to voltage in puller fan feed circuit (Light Blue wire). After repairs, go to step 64).
Replace A/C pressure sensor. After replacing pressure sensor, go to step 64).
Disconnect fan No. 2 relay electrical connector. If puller fan is on, go to step 58). If puller fan is not on, go to next step.
Probe terminal No. 86 (Dark Blue wire) in fan No. 2 relay harness connector with test light to ground. If test light illuminates, go to next step. If test light does not illuminate, go to step 63).
Turn ignition off. Disconnect PCM harness connector. Using test light connected to ground, probe terminal No. 86 (Dark Blue wire) in fan No. 2 relay harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 59).
Locate and repair short to ground in fan No. 2 relay driver circuit (Pink and Brown wires). After repairs, go to step 64).
Locate and repair short to voltage in pusher fan feed circuit (Black wire). After repairs, go to step 64).
Replace PCM. After replacing PCM, go to step 64).
Replace puller fan motor. After replacing puller fan motor, go to step 64).
Replace fan No. 1 relay. After replacing relay, go to step 64).
Replace pusher fan motor. After replacing pusher fan motor, go to step 64).
Replace fan No. 2 relay. After replacing relay, go to step 64).
Ensure engine coolant temperature is less than 212°F (100°C). Turn A/C off. Turn ignition on. If both fans are off, go to next step. If both fans are not off, go to step 3).
Select scan tool MISC. TESTS, RELAY CONTROL function. Command fan No. 1 on. If puller fan is running, go to next step. If puller fan is not running, go to step 6).
Select scan tool MISC. TESTS, RELAY CONTROL function. Command fan No. 2 on. Wait 6 seconds, then observe pusher fan. If pusher fan is running, system is operating normally at this time. If pusher fan is not running, go to step 19).

Auxiliary cooling fan operating voltage is available at all times from AUX FAN fuse (30-amp) located in underhood fuse/relay center. Voltage is provided from fuse through Orange wire which terminates at terminal No. 30 of auxiliary cooling fan relay. When relay coil is energized, relay contacts close to apply operating voltage to auxiliary cooling fan motor. Red wire connects relay terminal No. 87 to motor terminal "B". Motor is grounded from terminal "A" by Black wire to ground.

Auxiliary Cooling Fan Does Not Operate

If auxiliary cooling fan motor never operates, go to next step. If auxiliary cooling fan motor will not operate via auxiliary cooling fan temperature switch, go tostep 6). If auxiliary cooling fan motor will not operate via auxiliary cooling fan A/C pressure switch, go to step 7).
Remove auxiliary cooling fan relay from underhood fuse/relay center. Connect test light between auxiliary cooling fan relay terminal No. 30 (Orange wire) and ground. If test light illuminates, go to next step. If test light does not illuminate, locate and repair open circuit in Orange wire between auxiliary cooling fan relay and AUX FAN fuse in underhood fuse/relay center.
Turn ignition switch to RUN position. Connect a test light between auxiliary cooling fan relay terminal No. 85 (Pink wire) and ground. If test light illuminates, go to next step. If test light does not illuminate, locate and repair open circuit in Pink wire between IGN fuse (10-amp) and auxiliary cooling fan relay in underhood fuse/relay center.
Connect a fused jumper wire between auxiliary cooling fan relay terminals No. 30 (Orange wire) and No. 87 (Red wire). If auxiliary cooling fan motor runs, check for an open circuit in Light Green wire between splice and underhood fuse/relay center. If wiring is okay, replace auxiliary cooling fan relay. If auxiliary cooling fan motor does not run, go to next step.
Connect test light between auxiliary cooling fan motor connector terminal "A" (Black wire) and ground. If test light does not illuminate, locate and repair open circuit in Black wire between auxiliary cooling fan motor and ground. If test light illuminates, check for an open circuit in Red wire between underhood fuse/relay center and auxiliary cooling fan motor. If wiring is okay, replace cooling fan motor.
Disconnect auxiliary cooling fan temperature switch connector. Turn ignition switch to RUN position. Connect a fused jumper wire between auxiliary cooling fan temperature switch connector terminal "A" (Light Green wire) and ground. If auxiliary cooling fan motor runs, replace auxiliary cooling fan temperature switch. If auxiliary cooling fan motor does not run, locate and repair open circuit in Light Green wire between auxiliary cooling fan temperature switch and splice.
Disconnect auxiliary cooling fan A/C pressure switch connector. Turn ignition switch to RUN position. Connect a fused jumper from auxiliary cooling fan A/C pressure switch connector terminal "A" (Dark Green wire) and ground. If auxiliary cooling fan motor runs, check for an open circuit in Black wire between auxiliary cooling fan A/C pressure switch and ground. If wiring is okay, replace auxiliary cooling fan A/C pressure switch. If auxiliary cooling fan motor does not run, locate and repair open circuit in Dark Green wire between A/C high pressure switch and splice. Replace diode if open.

Auxiliary Cooling Fan Runs Continuously

Disconnect auxiliary cooling fan relay in underhood fuse/relay center. If auxiliary fan motor stops, go to next step. If auxiliary fan motor does not stop, locate and repair short to voltage in Red wire between underhood fuse/relay center and auxiliary cooling fan motor.
Connect a voltmeter between auxiliary cooling fan relay terminal No. 87 (Red wire) and ground. If voltage is less than 10 volts, replace auxiliary cooling fan relay. If voltage is more than 10 volts, go to next step.
Reconnect auxiliary cooling fan relay to underhood fuse/relay center. Disconnect auxiliary cooling fan temperature switch connector. If auxiliary cooling fan motor stops, replace auxiliary cooling fan temperature switch. If auxiliary cooling fan motor continues to run, go to next step.
Reconnect auxiliary cooling fan temperature switch connector. Disconnect A/C pressure switch connector. If auxiliary cooling fan motor stops, replace auxiliary cooling fan A/C pressure switch. If auxiliary cooling fan motor continues to run, check for short to ground in Light Green wire between underhood fuse/relay center and auxiliary cooling fan temperature switch, or in diode D100, diode D101, and Dark Green wire between auxiliary cooling fan A/C pressure switch. If circuit is okay, check the A/C control panel. See appropriate A/C-HEATER SYSTEM - MANUAL article.