Engine Cooling System: Diagnosis Buick LaCrosse II facelift

Diagnostic Code Index

DIAGNOSTIC CODE INDEX

Diagnostic Instructions

1. Perform the «Diagnostic System Check - Vehicle»(ref-621960-S18230123002014061000000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-621960-S06366559502014061000000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-621960-S11989915762014061000000) provides an overview of each diagnostic category.

Diagnostic Fault Information

KR20C Cooling Fan Low Speed Relay

KR20D Cooling Fan High Speed Relay

KR20E Cooling Fan Speed Control Relay

KR20F Cooling Fan Relay

Conditions for Running the DTC

1. The ignition voltage is greater than 11 volts.
2. The ECM driver transitions from ON to OFF or from OFF to ON.
3. DTCs P0480, P0481, P0691, P0692, P0693, and P0694 run continuously when the conditions above are met.

Conditions for Setting the DTC

The commanded state of the ECM driver and the actual state of the control circuit do not match for greater than 5 seconds.

Action Taken When the DTC Sets

DTCs P0480, P0481, P0691, P0692, P0693, P0694 are Type B DTCs.

Conditions for Clearing the MIL/DTC

DTCs P0480, P0481, P0691, P0692, P0693, P0694 are Type B DTCs.

Diagnostic Aids

1. The ECM has the capability of providing command to the fan relays even when a scan tool output control is being used. Always refer to the fan control command parameters on the scan tool to know which fans are being commanded ON by the ECM.
2. The scan tool cooling fan output control operates as follows: Cooling Fan Relay 1 operates both fans at a medium speed Cooling Fan Relays 2 and 3 operates both fans at a low speed Cooling Fan Relays 1, 2 and 3 operates both fans at a high speed
3. When disconnecting or removing fuses and relays from a fuse block, always inspect the component electrical terminals for corrosion and the correct orientation in the fuse block. Test the mating electrical terminals for tightness.
4. A condition with the powertrain relay may set DTC P0481 or P0693.

Circuit/System Testing

1. Ignition OFF, disconnect the KR20 Cooling Fan Relays listed below: KR20F Cooling Fan Relay KR20C Cooling Fan Low Speed Relay KR20D Cooling Fan High Speed Relay
2. Ignition ON, connect a test lamp between ground and the relay coil ignition voltage circuit terminal listed below. The test lamp should illuminate. KR20F Cooling Fan Relay terminal 85 KR20C Cooling Fan Low Speed Relay terminal 86 If the test lamp does not illuminate and the fuse is good Ignition OFF, and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Remove the test lamp. Test for less than 2 ohms in the ignition circuit of the appropriate relay, end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse. If the test lamp does not illuminate and the circuit fuse is open Ignition OFF, and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Remove the test lamp. Test for infinite resistance between the relay coil ignition circuits listed below and ground. KR20F Cooling Fan Relay terminal 85 KR20C Cooling Fan Low Speed terminal 86 If less than infinite resistance, repair the short to ground on the circuit. If infinite resistance test all the appropriate cooling fan relays for a shorted condition and replace as necessary. If the test lamp illuminates
3. Connect a DMM, set on the diode setting, between ground and a relay control circuit terminal listed below: KR20F Cooling Fan Relay terminal 86 KR20C Cooling Fan Low Speed Relay terminal 85 KR20D Cooling Fan High Speed Relay terminal 85
4. Verify the DMM reading is greater than 2.5 V or displays O.L with the cooling fan relays commanded OFF with a scan tool. If 2.5 V or less Ignition OFF, disconnect the X1 harness connector at the K20 Engine Control Module. Test for infinite resistance between the appropriate relay coil control circuit and ground. If less than infinite resistance, repair the short to ground on the circuit. If infinite resistance, replace the K20 Engine Control Module. If greater than 2.5 V or displays O.L.
5. Verify the DMM reading is less than 1 V when commanding the cooling fan relays ON with a scan tool. If 1 V or greater Ignition OFF, disconnect the X1 harness connector at the K20 Engine Control Module, ignition ON. Test for less than 1 V between the appropriate cooling fan relay control circuit and ground. If 1 V or greater, repair the short to voltage on the circuit. If less than 1 V. Ignition OFF, and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 2 ohms in the appropriate cooling fan relay control circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the K20 Engine Control Module. If less than 1 V
6. Test or replace the appropriate cooling fan relay.

Component Testing

1. Ignition OFF, disconnect a KR20 Cooling Fan Relay.
2. Test for 70-110 ohms between terminals 85 and 86, 95-135 ohms for the KR20F Cooling Fan Relay. If less than 70 ohms or greater than 110 ohms Replace the KR20 Cooling Fan Relay. If between 70-110 ohms
3. Test for infinite resistance between the terminals listed below. 30 and 86 30 and 87 30 and 85 85 and 87 If less than infinite resistance Replace the KR20 Cooling Fan Relay. If infinite resistance
4. Test for less than 2 ohms between terminals 3 and 4. If greater than 2 ohms Replace the KR20L Cooling Fan Speed Control 2 Relay. If less than 2 ohms
5. Connect a 20 A fused jumper wire between relay terminal 85 and B+. Connect a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms between terminals 30 and 87. If greater than 2 ohms replace the KR20 Cooling Fan Relay.

KR20 Relay with Single Digit Terminal ID

1. Ignition OFF, disconnect the KR20 cooling fan relay.
2. Test for 70-110 ohms between terminals 1 and 2, 95-135 ohms for the KR20F Cooling Fan Relay. If less than 70 ohms or greater than 135 ohms Replace the KR20 Cooling Fan Relay. If between 70-135 ohms
3. Test for infinite resistance between the terminals listed below. 3 and 1 3 and 5 3 and 2 2 and 5 If less than infinite resistance Replace the KR20 Cooling Fan Relay. If infinite resistance
4. Test for less than 2 ohms between terminals 3 and 4. If greater than 2 ohms Replace the KR20L Cooling Fan Speed Control 2 Relay. If less than 2 ohms
5. Connect a 20 A fused jumper wire between relay terminal 2 and B+. Connect a jumper wire between relay terminal 1 and ground. Test for less than 2 ohms between terminals 3 and 5. If greater than 2 ohms replace the KR20 Cooling Fan Relay.

1. Perform the «Diagnostic System Check - Vehicle»(ref-621960-S18230123002014061000000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-621960-S06366559502014061000000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-621960-S11989915762014061000000) provides an overview of each diagnostic category.

1. The ignition voltage is greater than 11 volts.
2. The ECM driver transitions from ON to OFF or from OFF to ON.
3. DTCs P0480, P0481, P0691, P0692, P0693, and P0694 run continuously when the conditions above are met.

The commanded state of the ECM driver and the actual state of the control circuit do not match for greater than 5 seconds.

DTCs P0480, P0481, P0691, P0692, P0693, and P0694 are Type B DTCs.

DTCs P0480, P0481, P0691, P0692, P0693, and P0694 are Type B DTCs.

1. The ECM has the capability of providing command to the fan relays even when a scan tool output control is being used. Always refer to the fan control command parameters on the scan tool to know which fans are being commanded ON by the ECM.
2. The scan tool cooling fan output control operates as follows: Cooling Fan Relay 1 operates both fans at a low speed Cooling Fan Relays 2 and 3 operates one fan at a high speed Cooling Fan Relays 1, 2 and 3 operates both fans at a high speed

1. Ignition OFF, disconnect all of the cooling fan relays. Ignition ON.
2. Verify that a test lamp illuminates between ground and a relay coil ignition circuit terminal listed below: KR20C Cooling Fan Low Speed Relay terminal 85/2 KR20D Cooling Fan High Speed Relay terminal 86/1 KR20E Cooling Fan Speed Control Relay terminal 86/1 If the test lamp does not illuminate Ignition OFF, and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Remove the test lamp. Test for less than 2 ohms in the ignition circuit of the appropriate cooling fan relay, end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse. If the test lamp does not illuminate and the circuit fuse is open Ignition OFF, and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Remove the test lamp. Test for infinite resistance between the appropriate cooling fan relay ignition circuit and ground. If less than infinite resistance, repair the short to ground on the circuit. If infinite resistance test or replace the appropriate cooling fan relay. If the test lamp illuminates
3. Ignition ON.
4. Connect a DMM, set on the diode setting, between ground and a relay control circuit terminal listed below: KR20C cooling fan low speed relay terminal 86/1 KR20D cooling fan high speed relay terminal 85/2 KR20E cooling fan speed control relay terminal 85/2
5. Verify the DMM reading is greater than 2.5 V or displays O.L with the cooling fan relays commanded OFF with a scan tool. If 2.5 V or less Ignition OFF, disconnect the X1 harness connector at the K20 Engine Control Module. Test for infinite resistance between the appropriate relay coil control circuit and ground. If less than infinite resistance, repair the short to ground on the circuit. If infinite resistance, replace the K20 Engine Control Module. If greater than 2.5 V or displays O.L.
6. Verify the DMM reading is less than 1 V when commanding the cooling fan relays ON with a scan tool. If 1 V or greater Ignition OFF, disconnect the X1 harness connector at the K20 Engine Control Module, ignition ON. Test for less than 1 V between the appropriate cooling fan relay control circuit and ground. If 1 V or greater, repair the short to voltage on the circuit. If less than 1 V. Ignition OFF, and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 2 ohms in the appropriate cooling fan relay control circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the K20 Engine Control Module. If less than 1 V
7. Test or replace the appropriate cooling fan relay.

1. Ignition OFF.
2. Disconnect a cooling fan relay.
3. Test for 70-110 ohms between terminals 85/2 and 86/1. If less than 70 ohms or greater than 110 ohms Replace the cooling fan relay. If between 70-110 ohms
4. Test for infinite resistance between the following terminals: 30 and 86 30 and 87 30 and 85 85 and 87 OR 3 and 2 3 and 5 3 and 1 1 and 5 If less than infinite resistance Replace the cooling fan relay. If infinite resistance
5. Test for less than 2 ohms between KR20E Cooling Fan Speed Control Relay terminals 30/3 and 87A/4. If 2 ohms or greater Replace the KR20E Cooling Fan Speed Control Relay. If less than 2 ohms
6. Install a 20 A fused jumper wire between relay terminal 85 or 2 and 12 V.
7. Install a jumper wire between relay terminal 86 or 1 and ground.
8. Test for less than 2 ohms between terminals 3/30 and 5/87. If 2 ohms or greater Replace the cooling fan relay. If less than 2 ohms
9. All OK.

1. Perform the «Diagnostic System Check - Vehicle»(ref-621960-S18230123002014061000000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-621960-S06366559502014061000000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-621960-S11989915762014061000000) provides an overview of each diagnostic category.

1. The engine is operating for greater than 30 seconds.
2. DTC P1258 runs continuously once the conditions above have been met.

The ECM detects that engine coolant temperature is warmer than 131°C (268°F) for greater than 2 seconds.

1. DTC P1258 is a Type A DTC.
2. The engine will operate in the Overheated Engine Protection Operating Mode.
3. The IP will illuminate the coolant temperature indicator lamp and the driver information center (DIC), if equipped, may display a message.
4. If the protection mode is active and an ECT sensor DTC sets, the protection mode will remain active at the start of the next drive cycle until the ECT sensor DTC runs and passes.

DTC P1258 is a Type A DTC.

1. Test the thermostat for correct operation. Refer to «Thermostat Diagnosis»(ref-621992-S35038130242014061000000) .
2. Test the engine cooling system for overheating. Refer to «Engine Overheating»(ref-621992-S39209209592014061000000) .
3. Inspect the water pump and coolant flow for correct operation. Refer to «Water Pump Cleaning and Inspection»(ref-622066-S38560818662014061000000) .
4. Inspect the engine mechanical for worn, leaking, cracked cylinder heads or engine block. Refer to «Coolant in Engine Oil»(ref-622050-S06838136182014061000000) .

Important Preliminary Inspections Before Starting

Before using the Symptom diagnosis, perform the following

1. Perform «Diagnostic System Check - Vehicle»(ref-621960-S18230123002014061000000) and verify all of the following items: Engine control module (ECM) and malfunction indicator lamp (MIL) are operating correctly. There are no diagnostic trouble codes (DTCs) stored. Scan tool data is within a normal operating range.
2. Verify the customer concern.
3. Perform the Visual/Physical Inspection in this section. The visual/physical inspection is extremely important, and can lead to correcting a condition without additional testing. It may also help reveal the cause of an intermittent condition.
4. Locate the correct symptom. Perform the tests and inspections associated with the symptom.

Review the entire cooling system operation in order to familiarize yourself with the system functions. Refer to Cooling Fan Description and Operation , and Cooling System Description and Operation .

Visual/Physical Inspection

Several of the symptom procedures call for a careful visual and physical inspection. This can lead to correcting a condition without further tests and can save time. This inspection should include the following

1. Ensure that the control module grounds are clean, tight, and correctly located.
2. Inspect cooling system hoses and pipes for splits, kinks, and improper connections. Inspect thoroughly for any type of leak or restriction.
3. Inspect for a dirty or restricted radiator or HVAC condenser.
4. Inspect for aftermarket devices which could affect the operation of the cooling system.
5. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.
6. Inspect the coolant recovery reservoir for proper coolant level.

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

1. «Cooling Fan Always On (LHU)»(ref-621992-S17398617322014061000000) , «Cooling Fan Always On (LUK or LFX)»(ref-621992-S19867229742014061000000)
2. «Cooling Fan Inoperative (LHU)»(ref-621992-S29352561392014061000000) , «Cooling Fan Inoperative (LUK or LFX)»(ref-621992-S10970095942014061000000)
3. «Engine Overheating»(ref-621992-S39209209592014061000000)
4. «Loss of Coolant»(ref-621992-S09600720432014061000000)
5. «Thermostat Diagnosis»(ref-621992-S35038130242014061000000)
6. «Engine Fails To Reach Normal Operating Temperature»(ref-621992-S31206584182014061000000)

1. Perform the «Diagnostic System Check - Vehicle»(ref-621960-S18230123002014061000000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-621960-S06366559502014061000000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-621960-S11989915762014061000000) provides an overview of the diagnostic category.

1. The scan tool cooling fan output control operates as follows: Cooling Fan Relay 1 operates both fans at a medium speed Cooling Fan Relay 2 and 3 operates both fans at a low speed Cooling Fan Relay 1, 2 and 3 operates both fans at a high speed
2. When disconnecting or removing fuses and relays from a fuse block, always inspect the component electrical terminals for corrosion and the correct orientation in the fuse block. Test the mating electrical terminals for tightness.

Both Fans ON

1. Ignition OFF, disconnect the KR20F cooling fan relay.
2. Ignition ON, verify that the cooling fans are not ON. If the cooling fans are OFF Test or replace KR20F relay. If the cooling fans are ON
3. Ignition OFF, disconnect the KR20C cooling fan low speed relay.
4. Ignition ON, verify that the cooling fans are not ON. If the cooling fans are OFF Test or replace KR20C relay. If the cooling fans are ON
5. Ignition OFF, disconnect the KR20M cooling fan left medium speed relay. If the cooling fans are OFF Test or replace KR20M relay. If the cooling fans are ON
6. Test for infinite resistance between ground and KR20F Cooling Fan Relay terminal 87. If less than infinite resistance repair the short to ground in the circuit If less than 1 V
7. Test for less than 1 V between ground and the relay terminals listed below KR20C Cooling Fan Low Speed Relay terminal 30 KR20M Cooling Fan Left Medium Speed Relay terminal 8 If greater than 1 V, repair the short to voltage on the appropriate circuit If less than 1 V
8. If all circuits test normal, test or replace the KR20M relay.

One Fan ON

1. Ignition OFF, disconnect the KR20D cooling fan high speed relay.
2. Ignition ON, verify that the cooling fan is not ON. If the cooling fans are OFF If the fan is OFF, test or replace KR20D relay. If the cooling fans are ON
3. Ignition OFF, disconnect the KR20N cooling fan right medium speed relay.
4. Ignition ON, verify that the cooling fan is not ON. If the cooling fans are OFF Test or replace KR20M relay. If the cooling fans are ON Test for less than 1 V between the relay circuit terminals listed below KR20D Cooling Fan High Speed Relay terminal 30 KR20N Cooling fan Right Medium Speed Relay terminal 8 If 1 V or greater repair the short to voltage on the circuit If the cooling fans are OFF
5. If all circuits test normal, test or replace the KR20N relay.

1. Perform the «Diagnostic System Check - Vehicle»(ref-621960-S18230123002014061000000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-621960-S06366559502014061000000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-621960-S11989915762014061000000) provides an overview of each diagnostic category.

1. The scan tool cooling fan output control operates as follows: Cooling Fan Relay 1 operates both fans at a low speed Cooling Fan Relays 2 and 3 operates one fan at a high speed Cooling Fan Relays 1, 2 and 3 operates both fans at a high speed
2. Certain resistance conditions with IAT or ECT sensors may cause unwarranted cooling fan activation. If the ECM is commanding the cooling fans ON for no apparent reason and without any component or system DTCs set, the IAT or ECT sensor may be skewed. If this condition is suspected, refer to the temperature versus resistance tables in the appropriate Engine Controls subsection.

Both Cooling Fans Always ON

1. Ignition OFF, disconnect KR20C Cooling Fan Low Speed Relay, ignition ON.
2. Verify that both cooling fans are OFF. If the cooling fans are ON Ignition OFF, disconnect the harness connector at the G10R Cooling Fan Motor-Right, ignition ON. Test for less than 1 V between KR20C Cooling Fan Low Speed Relay terminal 87/5 and ground. If 1 V or greater, repair the short to voltage in the relay controlled output circuit. If the cooling fans are OFF
3. Test or replace the KR20C Cooling Fan Low Speed Relay.

One Cooling Fan Always ON

1. Ignition OFF, disconnect the KR20D Cooling Fan High Speed Relay, ignition ON.
2. Verify the cooling fan is OFF. If the cooling fan is ON Ignition OFF, disconnect the harness connector at the G10L Cooling Fan Motor-Left, ignition ON. Test for less than 1 V between KR20D Cooling Fan High Speed Relay terminal 30/3 and ground. If 1 V or greater, repair the short to voltage in the relay controlled output circuit. If the cooling fan is OFF
3. Test or replace the KR20D Cooling Fan High Speed Relay.

1. Ignition OFF.
2. Disconnect a KR20 Cooling Fan Relay.
3. Test for 70-110 ohms between terminals 85/2 and 86/1. If less than 70 ohms or greater than 110 ohms Replace the KR20 cooling fan relay. If between 70-110 ohms
4. Test for infinite resistance between the following terminals: 30 and 86 30 and 87 30 and 85 85 and 87 OR 3 and 2 3 and 5 3 and 1 1 and 5 If less than infinite resistance Replace the KR20 Cooling Fan Relay. If infinite resistance
5. Test for less than 2 ohms between KR20E Cooling Fan Speed Control Relay terminals 30/3 and 87A/4. If 2 ohms or greater Replace the KR20E Cooling Fan Speed Control Relay. If less than 2 ohms
6. Install a 20 A fused jumper wire between relay terminal 85 or 2 and 12 V.
7. Install a jumper wire between relay terminal 86 or 1 and ground.
8. Test for less than 2 ohms between terminals 3/30 and 5/87. If 2 ohms or greater Replace the KR20 Cooling Fan Relay. If less than 2 ohms
9. All OK.

1. Perform the «Diagnostic System Check - Vehicle»(ref-621960-S18230123002014061000000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-621960-S06366559502014061000000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-621960-S11989915762014061000000) provides an overview of each diagnostic category.

1. The scan tool cooling fan output control operates as follows: Cooling Fan Relay 1 operates both fans at a medium speed Cooling Fan Relay 2 and 3 operates both fans at a low speed Cooling Fan Relay 1, 2 and 3 operates both fans at a high speed
2. When disconnecting or removing fuses and relays from a fuse block, always inspect the component electrical terminals for corrosion and the correct orientation in the fuse block. Test the mating electrical terminals for tightness.

1. Ignition OFF, disconnect the harness connectors, or remove the following components: KR20F Cooling Fan Relay KR20E Cooling Fan Speed Control Relay KR20L Cooling Fan Speed Control 2 Relay G10L Cooling Fan Motor-Left G10R Cooling Fan Motor-Right
2. Verify a test lamp illuminates between B+ and circuit terminal of the component listed below G10R Cooling Fan ground circuit terminal 3 KR20L Relay switched output circuit terminal 8 If the test lamp does not illuminate Test for less than 2 ohms in the appropriate ground circuit end to end. If less greater than 2 ohms, repair the open/high resistance in the circuit. If less than 2 ohms, repair the ground connection in the circuit. If the test lamp illuminates
3. Ignition ON, verify a test lamp illuminates between ground and the KR20 relay terminals listed below: KR20F relay terminal 85 KR20E relay terminal 86 and 30 If the test lamp does not illuminate and the fuse is good Ignition OFF, Disconnect the appropriate fuse. Test for less than 2 ohms between the fuse and the appropriate relay B+ end to end If greater than 2 ohms, repair the open/high resistance in the circuit. If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse. If the test lamp does not illuminate and the fuse is open Ignition OFF, Disconnect the appropriate fuse. Test for infinite resistance between the appropriate relay terminal and ground If less than infinite resistance, repair the short to ground. If infinite resistance, test or replace the KR20L Cooling Fan Speed Control 2 Relay. If the test lamp illuminates
4. Ignition OFF, install the KR20F relay.
5. Connect a test lamp between B+ and the KR20E relay coil control circuit terminal 85.
6. Ignition ON, command the cooling fans ON at medium speed with a scan tool. The test lamp should illuminate. If the test lamp does not illuminate Test for less than 2 ohms between the Cooling Fan Relay terminals listed below: KR20F Cooling Fan Relay terminal 87 KR20E Cooling Fan Speed Control Relay terminal 85 If greater than 2 ohms, repair the open/high resistance in the circuit. If less than 2 ohms, Test or replace the KR20F Cooling Fan Relay If the test lamp illuminates
7. Ignition OFF, install the KR20E relay.
8. Remove the KR20D Cooling Fan High Speed Relay.
9. Connect a test lamp between ground and the KR20D relay coil ignition circuit terminal 86.
10. Ignition ON, command the cooling fans ON at medium speed with a scan tool. The test lamp should illuminate. If the test lamp does not illuminate Test for less than 2 ohms between the Cooling Fan Relay terminals listed below: KR20D Cooling Fan High Speed Relay terminal 86 KR20E Cooling Fan Speed Control Relay terminal 87 If greater than 2 ohms, repair the open/high resistance in the circuit. If less than 2 ohms, Test or replace the KR20E Cooling Fan High Speed Relay. If the test lamp illuminates
11. Ignition OFF, install the KR20D relay.
12. Ignition ON, Connect a test lamp between ground and the G10 cooling fan harness connector terminal listed below. Command the cooling fans ON at high speed with a scan tool. The test lamp should illuminate at each terminal as commanded. G10L Cooling Fan Motor-Left terminal 1 G10R Cooling Fan Motor-Right terminal 1 If the test lamp does not illuminate and the fuse is good Ignition OFF, test for less than 2 ohms in the B+ circuit of the appropriate G10 Cooling Fan Motor end to end. If greater than 2 ohms, repair the open/high resistance in the circuit If less than 2 ohms, test or replace the appropriate KR20 Cooling Fan Relay. If the test lamp does not illuminate and the fuse is open Ignition OFF, Test for infinite resistance between the appropriate G10 Cooling Fan terminal 1 and ground. If less than infinite resistance, repair the short to ground. If infinite resistance, test or replace the appropriate G10 Cooling Fan. If the test lamp illuminates
13. Ignition OFF, remove the following relays from the underhood relay block X70: KR20M Cooling Fan Left Medium Speed Relay KR20N Cooling Fan Right Medium Speed Relay
14. Ignition ON, connect a test lamp between ground and harness terminal 4 of each relay listed below. The test lamp should illuminate at each terminal. KR20M Cooling Fan Left Medium Speed Relay KR20N Cooling Fan Right Medium Speed Relay KR20L Cooling Fan Speed Control 2 Relay If the test lamp does not illuminate. Test for less than 2 ohms between the B+ fuse and terminal 4 of the appropriate Cooling Fan Relay If greater than 2 ohms, repair the open/high resistance in the circuit. If the test lamp illuminates
15. Connect a test lamp between B+ and harness terminal 6 of each relay listed below. Command the cooling fans ON at medium speed. The test lamp should illuminate at each terminal as commanded. KR20M Cooling Fan Left Medium Speed Relay KR20N Cooling Fan Right Medium Speed Relay KR20L Cooling Fan Speed Control 2 Relay If the test lamp does not illuminate. Test for less than 2 ohms between KR20F Cooling Fan Relay terminal 87 and the appropriate relay terminal listed below: KR20M Cooling Fan Left Medium Speed Relay terminal 6 KR20N Cooling Fan Right Medium Speed Relay terminal 6 KR20L Cooling Fan Speed Control 2 Relay terminal 6 If greater than 2 ohms, repair the open/high resistance in the circuit. If less than 2 ohms, test or replace the KR20F Cooling Fan Relay If the test lamp illuminates
16. Ignition OFF, install the following relays: KR20M Cooling Fan Left Medium Speed Relay KR20N Cooling Fan Right Medium Speed Relay
17. Ignition ON, Connect a test lamp between ground and the G10 cooling fan harness connector terminal listed below. Command the cooling fans ON at medium speed with a scan tool. The test lamp should illuminate at each terminal as commanded. G10L Cooling Fan Motor-Left terminal 2 G10R Cooling Fan Motor-Right terminal 2 If the test lamp does not illuminate Test for less than 2 ohms in the appropriate relay switched output circuit end to end. If greater than 2 ohms, repair the open/high resistance in the circuit. If less than 2 ohms, test or replace the KR20M or KR20N Cooling Fan Relay as appropriate. If the test lamp illuminates
18. Ignition OFF, Connect the harness connectors to the G10 cooling fans.
19. Connect a 40 A fused jumper wire between terminal 2 and terminal 8 of the KR20L Speed Control 2 Relay harness connector.
20. Ignition ON, command the cooling fans ON at high speed with a scan tool. Both fans should operate at full speed. If the left cooling fan does not operate. Test for less than 2 ohms between the circuit terminals listed below: G10L Cooling Fan Motor Left terminal 3 KR20L Cooling Fan Speed Control 2 Relay terminal 2 If greater than 2 ohms, repair the open/high resistance in the circuit. If less than 2 ohms, test or replace the G10L Cooling Fan Motor. If the right cooling fan does not operate Test or replace the G10R Cooling Fan Motor Right If both fans operate
21. Command the cooling fans ON at medium speed with a scan tool. Both fans should operate at a medium speed. If either fan does not operate Test or replace the appropriate G10 cooling fan motor.
22. Ignition OFF, remove the jumper wire and install the KR20L Speed Control 2 Relay.
23. Ignition ON, command the cooling fans ON at low speed with a scan tool. Both fans should operate at a reduced speed. If both fans are OFF Test or replace, the KR20L Cooling Fan Speed Control 2 Relay.
24. If all of the circuits test normal, test or replace the KR20L Speed Control 2 Relay.

1. Ignition OFF, disconnect a KR20 Cooling Fan Relay.
2. Test for 70-110 ohms between terminals 85 and 86, 95-135 ohms for the KR20F Cooling Fan Relay. If less than 70 ohms or greater than 110 ohms Replace the KR20 Cooling Fan Relay. If between 70-110 ohms
3. Test for infinite resistance between the terminals listed below. 30 and 86 30 and 87 30 and 85 85 and 87 If less than infinite resistance Replace the KR20 Cooling Fan Relay. If infinite resistance
4. Test for less than 2 ohms between terminals 3 and 4. If greater than 2 ohms Replace the KR20L Cooling Fan Speed Control 2 Relay. If less than 2 ohms
5. Connect a 20 A fused jumper wire between relay terminal 85 and B+. Connect a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms between terminals 30 and 87. If greater than 2 ohms replace the KR20 Cooling Fan Relay.

G10 Engine Cooling Fan

1. Ignition OFF, disconnect the harness connector at the G10 engine cooling fan.
2. Connect a jumper wire between ground and the G10 ground circuit terminal 3.
3. Connect a 40 A fused jumper wire between B+ and the G10 fan B+ supply circuit terminal 1. The cooling fan should operate at a High speed. If the cooling fan does not operate Replace the G10 engine cooling fan. If the cooling fan operates
4. Connect a 40 A fused jumper wire between B+ and the G10 fan B+ supply circuit terminal 2. The cooling fan should operate at a reduced speed. If the cooling fan does not operate Replace the G10 engine cooling fan.

1. Perform the «Diagnostic System Check - Vehicle»(ref-621960-S18230123002014061000000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-621960-S06366559502014061000000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-621960-S11989915762014061000000) provides an overview of each diagnostic category.

1. The scan tool cooling fan output control operates as follows: Cooling Fan Relay 1 operates both fans at a low speed Cooling Fan Relays 2 and 3 operates one fan at a high speed Cooling Fan Relays 1, 2 and 3 operates both fans at a high speed

1. Ignition OFF, disconnect all of the KR20 Cooling Fan Relays.
2. Verify a test lamp illuminates between ground and the B+ circuit terminals listed below: KR20C Cooling Fan Low Speed B+ circuit terminal 30/3 KR20D Cooling Fan High Speed B+ circuit terminal 87/5 If the test lamp does not illuminate and the circuit fuse is good Disconnect the appropriate cooling fan fuse. Test for less than 2 ohms between the fuse and the appropriate relay B+ circuit terminal, end to end. If 2 ohms or greater, repair the open/high resistance in the B+ circuit. If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse. If the test lamp does not illuminate and the circuit fuse is open Connect a DMM to the appropriate relay B+ circuit terminal. Test for infinite resistance between the B+ circuit and ground. If less than infinite resistance, repair the short to ground on the B+ circuit. If infinite resistance Disconnect the harness connector at the appropriate G10 Cooling Fan Motor. Test for infinite resistance between the appropriate relay controlled output circuit terminal 87/5 and ground. KR20C Cooling Fan Low Speed output circuit terminal 87/5 KR20D Cooling Fan High Speed output circuit terminal 30/3 If less than infinite resistance, repair the short to ground on the circuit. If infinite resistance, test or replace the appropriate G10 Cooling Fan Motor. If the test lamp illuminates
3. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the G10L Cooling Fan Motor-Left. It may take up to 2 minutes for all vehicle systems to power down.
4. Test for less than 5 ohms between the circuits listed below and ground: G10L Cooling Fan Motor-Left terminal A KR20E Cooling Fan Speed Control Relay terminal 87/5 If 5 ohms or greater Ignition OFF and all vehicle systems OFF, it may take up to 2 minutes for all vehicle systems to power down. Test for less than 2 ohms in the appropriate ground circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, repair the open/high resistance in the ground connection. If less than 5 ohms
5. Connect the harness connector at the G10L Cooling Fan Motor-Left.
6. Connect a 50 A fused jumper between the KR20D Cooling Fan High Speed Relay terminals 30/3 and 87/5.
7. Verify the G10L Cooling Fan Motor-Left is activated at high speed. If the cooling fan does not activate Disconnect the harness connector at the G10L Cooling Fan Motor-Left. Test for less than 2 ohms in the circuit between KR20D Cooling Fan High Speed Relay terminal 30/3 and the G10L Cooling Fan Motor-Left terminal B. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the G10L Cooling Fan Motor-Left. If the cooling fan activates
8. Connect a fused jumper between the KR20E Cooling Fan Speed Control Relay switch circuit terminal 30/3 and the ground circuit terminal 87/5.
9. Connect a 40 A fused jumper between the KR20C Cooling Fan Low Speed Relay terminals 30/3 and 87/5.
10. Verify the G10R Cooling Fan Motor-Right is activated at high speed. If the cooling fan does not activate Disconnect the harness connector at the G10R Cooling Fan Motor-Right. Test for less than 2 ohms in the circuit between KR20C Cooling Fan Low Speed Relay terminal 87/5 and the G10R Cooling Fan Motor-Right terminal B. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms Test for less than 2 ohms in the circuit between KR20E Cooling Fan Speed Control Relay terminal 30/3 and the G10R Cooling Fan Motor-Right terminal A. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the G10R Cooling Fan Motor-Right. If the cooling fan activates
11. Install the KR20E Cooling Fan Speed Control Relay.
12. Verify both fan motors activate at low speed. If both cooling fans do not activate at low speed Disconnect both cooling fan motor harness connectors and the KR20E Cooling Fan Speed Control Relay. Test for less than 2 ohms in circuit between KR20E Cooling Fan Speed Control Relay terminal 87A/4 and the G10L Cooling Fan Motor-Left terminal B. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms Test for infinite resistance between KR20E Cooling Fan Speed Control Relay terminal listed below and ground. KR20E Cooling Fan Speed Control Relay terminal 30/3 KR20E Cooling Fan Speed Control Relay terminal 87A/4 If less than infinite, repair the short to ground in the circuit. If infinite, replace the KR20E cooling fan speed control relay. If both cooling fans activate
13. Test or replace the cooling fan relay listed below as appropriate: KR20C Cooling Fan Low Speed Relay KR20D Cooling Fan High Speed Relay

1. Ignition OFF.
2. Disconnect a KR20 Cooling Fan Relay.
3. Test for 70-110 ohms between terminals 85/2 and 86/1. If less than 70 ohms or greater than 110 ohms Replace the KR20 cooling fan relay. If between 70-110 ohms
4. Test for infinite resistance between the following terminals: 30 and 86 30 and 87 30 and 85 85 and 87 OR 3 and 2 3 and 5 3 and 1 1 and 5 If less than infinite resistance Replace the KR20 Cooling Fan Relay. If infinite resistance
5. Test for less than 2 ohms between KR20E Cooling Fan Speed Control Relay terminals 30/3 and 87A/4. If 2 ohms or greater Replace the KR20E Cooling Fan Speed Control Relay. If less than 2 ohms
6. Install a 20 A fused jumper wire between relay terminal 85 or 2 and 12 V.
7. Install a jumper wire between relay terminal 86 or 1 and ground.
8. Test for less than 2 ohms between terminals 3/30 and 87/5. If 2 ohms or greater Replace the KR20 Cooling Fan Relay. If less than 2 ohms
9. All OK.

Thermostat Diagnosis

Thermostat Diagnosis

1. Perform the «Diagnostic System Check - Vehicle»(ref-621960-S18230123002014061000000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-621960-S06366559502014061000000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-621960-S11989915762014061000000) provides an overview of each diagnostic category.

Note. The coolant heater cord will read Open due to an internal thermal switch if the ambient temperature is above -18°C (0°F).

1. Ignition OFF, disconnect the coolant heater cord from the E19 Coolant Heater.
2. Test for 40-55 ohms between the terminals of the E19 Coolant Heater. If not within 40-55 ohms Replace the E19 Coolant Heater. If within 40-55 ohms
3. Test for infinite resistance between each terminal of the E19 Coolant Heater and ground. If less than infinite resistance Replace the E19 Coolant Heater. If infinite resistance
4. Test or replace the coolant heater cord.

Thermostat Test Procedure Using Tempil Sticks

The coolant thermostat can be tested using a temperature (tempil) stick. The temperature stick is a pencil like device. It has a wax material containing certain chemicals which melt at a given temperature. Take a 87°C (188°F) tempil stick or a 97°C (206°F) tempil stick and rub it on the thermostat housing. Temperature sticks can be used to determine a thermostat's operating range.

1. Use a GE 24731 Tempil Stick in order to find the opening and the closing temperatures of the coolant thermostat. The 188 tempil stick melts at 87°C (188°F). The thermostat should begin to open. The 206 tempil stick melts at 97°C (206°F). The thermostat should be fully open.
2. Replace the coolant thermostat if it does not operate properly between this temperature range.

Thermostat Test Procedure Using Glycol

Inspect the operation of the thermostat by hanging the thermostat on a hook in a 50/50 percent solution of DEX-COOL® and clean drinkable water.

In order to inspect if the thermostat valve is opening properly, perform the following test

1. Completely submerge the thermostat in the glycol solution. The solution should be 11°C (22°F) above the temperature indicated on the thermostat valve.
2. Thoroughly agitate the solution. Under these conditions, the thermostat valve should open.

In order to inspect if the thermostat valve is closing properly, perform the following test

1. Completely submerge the thermostat in a glycol solution. The solution should be 6°C (10°F) below the temperature indicated on the thermostat valve.
2. Thoroughly agitate the solution. Under these conditions, the thermostat valve should close completely.

Pressure Cap Testing

1. Remove the pressure cap.
2. Wash the pressure cap sealing surface with water.
3. Use the EN-24460-A Cooling System Pressure Tester (1) with GE-42401-A Radiator Cap / Surge Tank Test Adapter (2) in order to test the pressure cap.
4. Test the pressure cap for the following conditions: Pressure release when the EN-24460-A Cooling System Pressure Tester exceeds the pressure rating of the pressure cap. Maintain the rated pressure for at least 10 seconds. Note the rate of pressure loss.
5. Replace the pressure cap under the following conditions: The pressure cap does not release pressure which exceeds the rated pressure of the cap. The pressure cap does not hold the rated pressure.

Cooling System Leak Testing

1. Remove the pressure cap.
2. Test the operation of the pressure cap. Refer to «Pressure Cap Testing»(ref-621992-S14847478142014061000000) .
3. Wash the pressure cap mating surface with water.
4. Use the EN-24460-A Cooling System Pressure Tester (1) with GE-42401-3 Radiator Cap / Surge Tank Test Adapter (2) in order to apply pressure to the cooling system. Do not exceed the pressure cap rating.
5. The cooling system should hold the rated pressure for at least 2 minutes. Observe the gauge for any pressure loss.
6. Repair any leaks as required.