Engine Cooling System: Diagnosis Chevrolet Sonic I

Diagnostic Code Index

DIAGNOSTIC CODE INDEX

Diagnostic Instructions

1. Perform the «Diagnostic System Check - Vehicle»(ref-542476-S03610919532013041600000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-542476-S11988299792013041600000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-542476-S27446858652013041600000) provides an overview of each diagnostic category.

Diagnostic Fault Information

Typical Scan Tool Data

Radiator Coolant Temperature Sensor

Conditions for Running the DTC

P00B3

1. The engine run time is greater than 10 s.
2. The intake air temperature (IAT) is colder than 70°C (158°F).
3. The DTC runs continuously when the above conditions are met.

P00B4

1. The engine run time is greater than 60 s.
2. The intake air temperature (IAT) is warmer than -7°C (19°F).
3. The DTC runs continuously when the above conditions are met.

Conditions for Setting the DTC

P00B3

The ECM detects that the RCT sensor is warmer than 149°C (300°F) for greater than 10 s.

P00B4

Note. The scan tool only displays to -40°C (-40°F).

The ECM detects that the RCT sensor is colder than -60°C (-76°F) for greater than 10 s.

Action Taken When the DTC Sets

DTC P00B3 and P00B4 are Type B DTCs.

Conditions for Clearing the MIL/DTC

DTC P00B3 and P00B4 are Type B DTCs.

Diagnostic Aids

Note. The engine coolant temperature (ECT) sensor is mounted on the engine and the radiator coolant temperature (RCT) sensor is mounted on the radiator.

1. As the thermostat opens, the RCT sensor temperature should rise steadily, then stabilize once the thermostat opens completely.
2. Test the RCT sensor at various temperature levels in order to evaluate the possibility of a skewed sensor.
3. If the vehicle has sat for greater than 8 hours, the ECT sensor and the RCT sensor values should display within 3°C (5°F).

Circuit/System Testing

1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the B34B Engine Coolant Temperature Sensor. It may take up to 2 min for all vehicle systems to power down.
2. Test for less than 5 ohms between the low reference circuit terminal 1 and ground. If 5 ohms or greater Ignition OFF, disconnect the harness connector at the K20 Engine Control Module. Test for less than 2 ohms in the low reference 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 5 ohms
3. Ignition ON.
4. Verify the scan tool Radiator Coolant Temperature Sensor parameter is colder than -39°C (-38°F). If warmer than -39°C (-38°F) Ignition OFF, disconnect the harness connector at the K20 Engine Control Module. Test for infinite resistance between the signal circuit terminal 2 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 colder than -39°C (-38°F)
5. Install a 3 A fused jumper wire between the signal circuit terminal 2 and the low reference circuit terminal 1.
6. Verify the scan tool Radiator Coolant Temperature sensor parameter is warmer than 137°C (280°F). If colder than 137°C (280°F) Ignition OFF, remove the jumper wire, disconnect the harness connector at the K20 Engine Control Module. Test for less than 1 V between the signal circuit and ground. If 1 V or greater, repair the short to voltage on the circuit. If less than 1 V Ignition OFF. Test for less than 2 ohms in the signal 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 warmer than 137°C (280°F)
7. Test or replace the B34B Engine Coolant Temperature Sensor.

Component Testing

1. Ignition OFF, disconnect the harness connector at the B34B Engine Coolant Temperature Sensor.
2. Test the RCT sensor by varying the sensor temperature while monitoring the sensor resistance. Compare the readings with the «Temperature Versus Resistance»(ref-542500-S03034854432013041600000) table. The resistance values should be in range of the table values. If not within the specified range Replace the B34B Engine Coolant Temperature Sensor. If within the specified range
3. Test for infinite resistance between each terminal and the sensor housing. If less than infinite resistance Replace the B34B Engine Coolant Temperature Sensor. If infinite resistance
4. All OK.

1. Perform the «Diagnostic System Check - Vehicle»(ref-542476-S03610919532013041600000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-542476-S11988299792013041600000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-542476-S27446858652013041600000) provides an overview of each diagnostic category.

Radiator Coolant Temperature Sensor

Circuit Description

The engine coolant temperature sensor is a variable resistor that measures the temperature of the engine coolant in the radiator. The engine control module (ECM) supplies 5 volts to the engine coolant temperature signal circuit and supplies a ground to the low reference circuit. The purpose of this diagnostic is to determine if the input from the RCT sensor is skewed warmer than normal. The internal clock of the ECM will record the amount of time the engine is OFF. If the required engine OFF time is met at start-up, the ECM will compare the temperature difference between the actual measured RCT and ECT sensors.

The following table illustrates the difference between temperature, resistance, and voltage

1. DTCs P00B3, P00B4, P00B6, P0112, P0113, P0117, P0118, P0502, P0503 or P2610 are not set.
2. The vehicle has been OFF for greater than 8 hours before vehicle ON.
3. The vehicle is ON, or the engine is running.
4. The intake air temperature (IAT) is warmer than -7°C (19°F).
5. The fuel level is greater than 10 percent.
6. The DTC runs once per ignition cycle when the above conditions are met.

The ECM determines the absolute difference of temperature between the RCT start up temperature and ECT start up temperature is greater than 20°C (68°F) .

DTC P00B6 is a Type B DTC.

DTC P00B6 is a Type B DTC.

1. As the thermostat opens, the radiator coolant temperature sensor signal should rise steadily, then stabilize once the thermostat opens completely.
2. Inspect for the correct operation of the engine cooling system and verify the correct coolant level.

1. Vehicle OFF, disconnect the harness connector at the B34B engine coolant temperature sensor.
2. Vehicle OFF, all systems OFF. This may take up to 2 minutes for all vehicle systems to power down. Test for less than 5 ohms between the low reference circuit terminal 1 and ground. If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the K20 engine control module.
3. Vehicle ON, verify the scan tool Radiator Coolant Temperature Sensor parameter is at -40°C (-40°F). If warmer than the specified range, test the signal circuit terminal 2 for a short to ground. If the circuit tests normal, replace the K20 engine control module.
4. Install a 1 A fused jumper wire between the signal circuit terminal 2 and the low reference circuit terminal 1. Verify the scan tool Radiator Coolant Temperature Sensor parameter is at 140°C (284°F). If less than specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K20 engine control module.
5. If all circuits test normal, test or replace the B34B engine coolant temperature sensor.

1. Vehicle OFF, remove the B34B engine coolant temperature sensor.
2. Test the engine coolant temperature sensor by varying the sensor temperature while monitoring the sensor resistance. Compare the readings with the «Temperature Versus Resistance»(ref-542500-S03034854432013041600000) table and verify that the resistance is within 5 percent of the specification. If not within the specified range, replace the B34B engine coolant temperature sensor.

1. Perform the «Diagnostic System Check - Vehicle»(ref-542476-S03610919532013041600000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-542476-S11988299792013041600000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-542476-S27446858652013041600000) provides an overview of each diagnostic category.

Radiator Coolant Temperature Sensor

The engine control module (ECM) monitors the temperature of the engine radiator coolant. The ECM controls the thermostat with a pulse width modulated (PWM) signal. The ECM compares the radiator coolant temperature to the engine coolant temperature in order to determine if there sufficient coolant flow through the thermostat.

1. DTCs P00B3, P00B4, P00B6, P0116, P0117, and P0118 are not set.
2. The engine run time is greater than 5 m. OR
3. The engine coolant temperature is greater than 105°C (221°F).
4. The DTC runs continuously when the above conditions are met.

Note. The scan tool display range is between -40 and + 150°C (-40 and +302°F).

The ECM detects the difference between the RCT sensor and the ECT sensor is greater than 30°C (86°F) when the ECT sensor is warmer than 117°C (242°F) for greater than 5 s.

DTC P00B7 is a Type B DTC.

DTC P00B7 is a Type B DTC.

1. The thermostat has a mechanical fail-safe in case of an electrical condition with the thermostat heater. The mechanical thermostat will open at approximately 80°C (176°F). The mechanical thermostat will cycle from approximately 85°C (185°F) to approximately 102°C (215°F).
2. A resistance condition in the RCT sensor circuits may cause this DTC. This condition results in a greater voltage on the RCT sensor signal circuit, which is interpreted by the ECM as a colder RCT.

1. Vehicle OFF, inspect the cooling system for the conditions below. Refer to «Symptoms - Engine Cooling»(ref-542500-S38701010902013041600000) . Weak coolant solution Obstructed radiator air flow or bent radiator fins Blocked cooling system passages Radiator hoses that are restricted, collapsed, or deteriorated Damaged water pump and or belt Loss of cooling system pressure Leaking surge tank cap Radiator hoses Cylinder head or an engine block that is cracked or plugged If you find any of the above conditions, repair as necessary.
2. If all conditions test normal, replace the E41 engine coolant thermostat heater.

1. Perform the «Diagnostic System Check - Vehicle»(ref-542476-S03610919532013041600000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-542476-S11988299792013041600000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-542476-S27446858652013041600000) provides an overview of each diagnostic category.

1. The ignition voltage is 11-18 volts.
2. The engine speed is 400 RPM or greater.
3. The ECM has commanded the output driver ON and OFF at least once during the ignition cycle.
4. The DTCs 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 the fan at low speed Cooling Fan Relay 2 operates the fan 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.

1. Ignition OFF, disconnect the cooling fan relays listed below: KR20C Cooling Fan Low Speed Relay KR20D Cooling Fan High Speed Relay
2. Ignition ON, verify that a test lamp illuminates between the relay coil ignition circuit terminal listed below and ground: KR20C Cooling Fan Low Speed Relay terminal 86 KR20D Cooling Fan High Speed Relay terminal 86 If the test lamp does not illuminate Ignition OFF, 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, remove the test lamp. Test for infinite resistance between the relay coil ignition circuits listed below and ground: KR20C Cooling Fan Low Speed Relay terminal 85 KR20D Cooling Fan High Speed Relay terminal 85 If less than infinite resistance, repair the short to ground in the circuit. If infinite resistance, test all of the appropriate cooling fan relays for a shorted condition and replace as necessary. If the test lamp illuminates
3. Ignition OFF, remove the test lamp, ignition ON.
4. Connect a DMM, set on the diode setting, between a control circuit terminal listed below and ground: KR20C Cooling Fan Low Speed Relay terminal 86 KR20D Cooling Fan High Speed relay terminal 86
5. Verify the DMM reading is greater than 2.5 V or displays O.L. 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. 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 of the cooling fan relay. If less than or greater than the specified range Replace the cooling fan relay. If within the specified range
4. Test for infinite resistance between following terminals: 30/3 and 86/1 30/3 and 87/5 30/3 and 85/2 85/2 and 87/5 If less than infinite resistance Replace the cooling fan relay. If infinite resistance
5. Install a 20 A fused jumper wire between relay terminal 85/2 and 12 V.
6. Install a jumper wire between relay terminal 86/1 and ground.
7. Test for less than 2 ohms between terminals 30/3 and 87/5. If 2 ohms or greater Replace the cooling fan relay. If less than 2 ohms
8. All OK.

1. Perform the «Diagnostic System Check - Vehicle»(ref-542476-S03610919532013041600000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-542476-S11988299792013041600000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-542476-S27446858652013041600000) provides an overview of each diagnostic category.

KR20C Cooling Fan Low Speed Relay

KR20D Cooling Fan High Speed Relay

KR20E Cooling Fan Speed Control Relay

KR20F Cooling Fan Relay

KR20P Cooling Fan Medium Speed Relay

LUV or LFF- ECM with 2 Face Mounted Connectors

1. The ignition voltage is between 11-32 volts.
2. The engine speed is 400 RPM or greater.
3. The ECM has commanded the output driver ON and OFF at least once during the ignition cycle.
4. DTCs P0480 and P0481 run continuously when the conditions above are met.

LUJ- ECM with 3 Face Mounted Connectors

1. The ignition voltage is 11 volts or greater.
2. The ECM has commanded the output driver ON and OFF at least once during the ignition cycle.
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.

1. DTCs P0480, P0481, P0691, P0692, P0693, and P0694 are Type B DTCs - LUV or LFF.
2. DTCs P0480, P0481, P0691, P0692, P0693, and P0694 are Type C DTCs - LUJ.

1. DTCs P0480, P0481, P0691, P0692, P0693, and P0694 are Type B DTCs - LUV or LFF.
2. DTCs P0480, P0481, P0691, P0692, P0693, and P0694 are Type C DTCs - LUJ.

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 scan tool Cooling Fan Relay Command parameters 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 the fan at a low speed Cooling Fan Relay 2 and 3 operates the fan at a medium speed Cooling Fan Relay 1, 2 and 3 operates the fan 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 test the mating electrical terminals for tightness.

1. Ignition OFF, disconnect the cooling fan relays listed below: KR20F Cooling Fan Relay KR20P Cooling Fan Medium Speed Relay KR20D Cooling Fan High Speed Relay
2. Ignition ON, verify that a test lamp illuminates between ground and the relay coil ignition circuit terminal listed below: KR20F Cooling Fan Relay terminal 85 KR20P Cooling Fan Medium 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 fuse that supplies ignition voltage to the coil side of the cooling fan relays. Test for less than 2 ohms between the ignition circuit terminal of the appropriate cooling fan relay and the fuse. 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. Test for infinite resistance between the relay coil ignition circuits listed below and ground: KR20F Cooling Fan Relay terminal 85 KR20D Cooling Fan High Speed Relay terminal 86/1 If less than infinite resistance, repair the short to ground in the circuit. If infinite resistance, test all of the appropriate cooling fan relays for a shorted condition and replace as necessary. If the test lamp illuminates
3. Ignition OFF, remove the test lamp, ignition ON.
4. Connect a DMM, set on the diode setting, between a control circuit terminal listed below and ground: KR20F cooling fan relay terminal 86 KR20P cooling fan medium speed relay terminal 85 KR20D cooling fan high speed relay terminal 85/2
5. Verify the DMM reading is greater than 2.5 V or displays O.L. If 2.5 V or less Ignition OFF, and all vehicle systems OFF, it may take up to 2 minutes for all vehicle systems to power down. Disconnect the harness connector X1 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 harness connector X1 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. 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 or greater than the specified range Replace the cooling fan relay. If within the specified range
4. Test for infinite resistance between the following terminals: 30/3 and 86/1 30/3 and 87/5 30/3 and 85/2 85/2 and 87/5 If less than infinite resistance Replace the cooling fan relay. If infinite resistance
5. Install a 20 A fused jumper wire between relay terminal 85/2 and 12 V.
6. Install a jumper wire between relay terminal 86/1 and ground.
7. Test for less than 2 ohms between terminals 30/3 and 87/5. If 2 ohms or greater Replace the cooling fan relay. If less than 2 ohms
8. All OK.

1. Perform the «Diagnostic System Check - Vehicle»(ref-542476-S03610919532013041600000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-542476-S11988299792013041600000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-542476-S27446858652013041600000) provides an overview of each diagnostic category.

Conditions for Running the DTCs

1. The ignition is ON, or the engine is running.
2. The DTCs run continuously once the above condition is met

The ECM detects that the commanded state of the driver and the actual state of the control circuit do not match for greater than 15 seconds.

1. DTCs P0597, P0598, and P0599 are Type B DTCs.
2. The engine control module commands the engine cooling fans ON.

Conditions for Clearing the DTC

DTCs P0597, P0598, and P0599 are Type B DTCs.

1. A low engine coolant level could cause the thermostat heater to overheat and set a DTC.
2. The thermostat has a mechanical fail-safe in case of an electrical condition with the thermostat heater. The mechanical thermostat will open at approximately 80°C (176°F). The mechanical thermostat will cycle from approximately 85°C (185°F) to approximately 102°C (215°F).

1. Ignition OFF, disconnect the harness connector at the E41 Engine Coolant Thermostat Heater, Ignition ON.
2. Verify that a test lamp illuminates between the ignition circuit terminal 2 and ground. If the test lamp does not illuminate and the circuit fuse is good Ignition OFF, remove the test lamp. Test for less than 2 ohms in the ignition circuit 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, remove the test lamp. Test for infinite resistance between the ignition circuit and ground. If less than infinite resistance, repair the short to ground in the circuit. If infinite resistance, test all the components connected to fuse and replace as necessary. If the test lamp illuminates
3. Verify that a test lamp does not illuminate between the ignition circuit terminal 2 and the control circuit terminal 1. If the test lamp illuminates Ignition OFF, disconnect the harness connector at the K20 Engine Control Module. Test for infinite resistance between the 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 the test lamp does not illuminate
4. Remove the test lamp, command the E41 Engine Coolant Thermostat Heater ON with a scan tool.
5. Verify the scan tool E41 Engine Coolant Thermostat Heater Control Circuit High Voltage Test Status parameter displays OK. If OK is not displayed Ignition OFF, disconnect the harness connector at the K20 Engine Control Module, ignition ON. Test for less than 1 V between the control circuit and ground. If 1 V or greater, repair the short to voltage on the circuit. If less than 1 V, replace the K20 Engine Control Module. If OK is displayed
6. Install a 3 A fused jumper wire between the control circuit terminal 1 and the ignition circuit terminal 2.
7. Verify the scan tool Engine Coolant Thermostat Heater Circuit High Voltage Test Status parameter is displaying Malfunction when commanding the E41 Engine Coolant Thermostat Heater ON with a scan tool. If Malfunction is not displayed Ignition OFF, remove the jumper wire, disconnect the harness connector at the K20 Engine Control Module. Test for less than 2 ohms in the 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 Malfunction is displayed
8. Test or replace the E41 Engine Coolant Thermostat Heater.

1. Perform the «Diagnostic System Check - Vehicle»(ref-542476-S03610919532013041600000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-542476-S11988299792013041600000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-542476-S27446858652013041600000) provides an overview of each diagnostic category.

1. DTCs P00B3, P00B4, P00B6, P0101, P0102, P0103, P0111, P0112, P0113, P0114, P0116, P0117, or P0118 are not set.
2. The engine run time is between 70 s and 30 min.
3. The engine coolant temperature (ECT) sensor at start-up is between -10°C to +59°C (14°F to 138°F).
4. The intake air temperature (IAT) sensor is between -7°C to +60°C (-4°F to +140°F).
5. The airflow into the engine is between 1 to 100 g/s.
6. The DTC runs once per ignition cycle when the above conditions are met.

The ECM detects the engine coolant thermostat is stuck open for at least 2.5 min.

DTC P2181 is a Type B DTC

DTC P2181 is a Type B DTC

1. Insufficient vehicle interior heating is an indication of improper thermostat operation.
2. The scan tool Desired ECT Sensor and the ECT Sensor parameters should be within 5°C (9°F) when the engine is at operating temperature.
3. A resistance condition in the ECT sensor circuits may cause this DTC. This condition results in a greater voltage on the ECT sensor signal circuit, which is interpreted by the ECM as a colder ECT.

Important Preliminary Inspections Before Starting

Before using the Symptom diagnosis, perform the following

1. Perform «Diagnostic System Check - Vehicle»(ref-542476-S03610919532013041600000) 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 (LUV) , Cooling Fan Description and Operation (LWE, LUW) , 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 surge tank 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 (LUV)»(ref-542500-S01314013672013041600000) , «Cooling Fan Always On (LUW, LWE)»(ref-542500-S15985734392013041600000)
2. «Cooling Fan Inoperative (LUV)»(ref-542500-S19440832022013041600000) , «Cooling Fan Inoperative (LUW, LWE)»(ref-542500-S12084670822013041600000)
3. «Engine Overheating»(ref-542500-S42044585912013041600000)
4. «Loss of Coolant»(ref-542500-S42302016122013041600000)
5. «Thermostat Diagnosis»(ref-542500-S05639644292013041600000)
6. «Engine Fails To Reach Normal Operating Temperature»(ref-542500-S15029887472013041600000)

1. Perform the «Diagnostic System Check - Vehicle»(ref-542476-S03610919532013041600000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-542476-S11988299792013041600000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-542476-S27446858652013041600000) provides an overview of the diagnostic category.

1. The scan tool cooling fan output control operates as follows: Cooling Fan Relay 1 operates the fan at a low speed Cooling Fan Relay 2 and 3 operates the fan at a medium speed Cooling Fan Relay 1, 2 and 3 operates the fan at a high speed
2. Certain resistance conditions with intake air temperature (IAT) or engine coolant temperature (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 Specifications of the appropriate engine controls subsection.
3. If the cooling fan operates at high speed when the ECM is requesting medium speed operation, test or replace the KR20E Cooling Fan Speed Control Relay.

1. Ignition OFF, disconnect each cooling fan relay one at a time, in the order listed below, ignition ON: KR20F Cooling Fan Relay KR20C Cooling Fan Low Speed Relay KR20P Cooling Fan Medium Speed Relay KR20D Cooling Fan High Speed Relay
2. Verify that the cooling fan is not activated after each relay is removed. If the cooling fan is ON with all of the listed relays removed Ignition OFF, disconnect the harness connector at the R10 Cooling Fan Resistor, ignition ON. Test for less than 1 V between the relay controlled output circuit terminal listed below and ground: KR20C Cooling Fan Low Speed Relay terminal 87 KR20P Cooling Fan Medium Speed Relay terminal 87 KR20D Cooling Fan High Speed Relay terminal 87/5 If 1 V or greater, repair the short to voltage in the appropriate circuit. If the cooling fan is OFF after a listed relay is removed
3. 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 or greater than the specified range Replace the cooling fan relay. If within the specified range
4. Test for infinite resistance between the following terminals: 30/3 and 86/1 30/3 and 87/5 30/3 and 85/2 85/2 and 87/5 If less than infinite resistance Replace the cooling fan relay. If infinite resistance
5. Install a 20 A fused jumper wire between relay terminal 85/2 and 12 V.
6. Install a jumper wire between relay terminal 86/1 and ground.
7. Test for less than 2 ohms between terminals 30/3 and 87/5. If 2 ohms or greater Replace the cooling fan relay. If less than 2 ohms
8. All OK.

1. Perform the «Diagnostic System Check - Vehicle»(ref-542476-S03610919532013041600000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-542476-S11988299792013041600000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-542476-S27446858652013041600000) provide 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 Relay 2 operates one fan 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.

Cooling Fan Always ON

1. Ignition OFF, disconnect KR20C Cooling Fan Low Speed Relay and KR20D Cooling Fan High Speed Relay, ignition ON.
2. Verify that the cooling fan is OFF. If the cooling fan is ON Ignition OFF, disconnect the harness connector at the G10R Cooling Fan Motor, ignition ON. Test for less than 1 V between the appropriate output control circuit terminal 87 and ground. If 1 V or greater, repair the short to voltage in the circuit. If the cooling fan is OFF
3. Test or replace the appropriate cooling fan relay.

1. Ignition OFF.
2. Disconnect the 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 appropriate 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 If less than infinite resistance Replace the appropriate KR20 Cooling Fan Relay. If infinite resistance
5. Install a 20 A fused jumper wire between relay terminal 85 or 2 and 12 V.
6. Install a jumper wire between relay terminal 86 or 1 and ground.
7. Test for less than 2 ohms between terminals 3/30 and 5/87. If 2 ohms or greater Replace appropriate the KR20 Cooling Fan Relay. If less than 2 ohms
8. All OK.

1. Perform the «Diagnostic System Check - Vehicle»(ref-542476-S03610919532013041600000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-542476-S11988299792013041600000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-542476-S27446858652013041600000) provides an overview of each diagnostic category.

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

Inoperative in All Speeds

1. Ignition OFF, disconnect the harness connector at the R10 Cooling Fan Resistor.
2. Verify a test lamp illuminates between the ground circuit terminal 1 and B+. If the test lamp does not illuminate Ignition OFF, remove the test lamp. Test for less than 2 ohms in the 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 the test lamp illuminates
3. Test or replace the G10 Cooling Fan Motor. Replace the cooling fan fuses if necessary.

Low, Medium, or High Speed Inoperative

1. Ignition OFF.
2. Disconnect the following cooling fan relays, ignition ON: KR20C Cooling Fan Low Speed Relay KR20D Cooling Fan High Speed Relay KR20E Cooling Fan Speed Control Relay KR20F Cooling Fan Relay KR20P Cooling Fan Medium Speed Relay
3. Verify a test lamp illuminates between ground and each of the cooling fan relay B+ circuit terminals listed below: KR20C Cooling Fan Low Speed Relay terminal 30 KR20D Cooling Fan High Speed Relay terminal 30/3 KR20P Cooling Fan Medium Speed Relay terminal 30 If the test lamp does not illuminate and the circuit fuse is good Ignition OFF, remove the test lamp. Test for less than 2 ohms in the appropriate relay B+ circuit, 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, disconnect the harness connector at the R10 Cooling Fan Resistor. Test for infinite resistance between the appropriate relay controlled output circuit terminal listed below and ground: KR20C Cooling Fan Low Speed Relay terminal 87 KR20D Cooling Fan High Speed Relay terminal 87/5 KR20P Cooling Fan Medium Speed Relay terminal 87 If less than infinite resistance, repair the short to ground in the circuit. If infinite resistance, test or replace the G10 Cooling Fan Motor, replace the fuse as necessary. If the test lamp illuminates
4. Verify a test lamp illuminates between the KR20F Cooling Fan Relay output circuit terminal 87 and B+. If the test lamp does not illuminate Ignition OFF, remove the test lamp. Test for less than 2 ohms in the 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 the test lamp illuminates
5. Ignition OFF, Install the KR20F Cooling Fan Relay, ignition ON.
6. Verify a test lamp illuminates between each of the cooling fan relay ignition circuit terminals listed below and ground: KR20C Cooling Fan Low Speed Relay terminal 86 KR20E Cooling Fan Speed Control Relay terminal 85 and 30 If the test lamp does not illuminate at each terminal Ignition OFF, remove the test lamp. Test for less than 2 ohms between the appropriate relay ignition circuit terminal and the fuse. 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 illuminates at each terminal
7. Command the cooling fan ON at low speed with a scan tool.
8. Verify a test lamp illuminates between B+ and each of the relay control circuit terminals listed below: KR20C Cooling Fan Low Speed Relay terminal 85 KR20E Cooling Fan Speed Control Relay terminal 86 If the test lamp does not illuminate Ignition OFF, remove the test lamp and disconnect the KR20F Cooling Fan Relay. Test for less than 2 ohms between the KR20F Cooling Fan Relay terminal 30 and the relay control circuit terminals listed below: KR20C Cooling Fan Low Speed Relay terminal 85 KR20E Cooling Fan Speed Control Relay terminal 86 If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the KR20F Cooling Fan Relay. If the test lamp illuminates
9. Ignition OFF, install the KR20E Cooling Fan Speed Control Relay, ignition ON.
10. Command the cooling fan ON at low speed with a scan tool.
11. Verify a test lamp illuminates between the KR20D Cooling Fan High Speed Relay ignition circuit terminal 85/1 and ground. If the test lamp does not illuminate Ignition OFF, remove the test lamp and disconnect the KR20E Cooling Fan Speed Control Relay. Test for less than 2 ohms between the KR20D Cooling Fan High Speed Relay terminal 85/1 and KR20E Cooling Fan Speed Control Relay terminal 87. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the KR20E Cooling Fan Speed Control Relay. If the test lamp illuminates
12. Ignition OFF, install all of the previously removed cooling fan relays. Disconnect the harness connector at the R10 Cooling Fan Resistor, ignition ON.
13. Command the cooling fan ON at high speed with a scan tool.
14. Verify a test lamp illuminates between ground and each of the R10 Cooling Fan Resistor circuit terminals listed below: R10 Cooling Fan Resistor low speed circuit terminal 2 R10 Cooling Fan Resistor medium speed circuit terminal 3 R10 Cooling Fan Resistor high speed circuit terminal 4 If the test lamp does not illuminate at each terminal Ignition OFF, remove the test lamp. Disconnect the appropriate relay from the list below: KR20C Cooling Fan Low Speed Relay KR20D Cooling Fan High Speed Relay KR20P Cooling Fan Medium Speed Relay Test for less than 2 ohms in the relay controlled output circuit, end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, test or replace the relay. If the test lamp illuminates at each terminal
15. Test or replace the G10 Cooling Fan Motor.

Relay Test

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 or greater than the specified range Replace the cooling fan relay. If within the specified range
4. Test for infinite resistance between the following terminals: 30/3 and 86/1 30/3 and 87/5 30/3 and 85/2 85/2 and 87/5 If less than infinite resistance Replace the cooling fan relay. If infinite resistance
5. Install a 20 A fused jumper wire between relay terminal 85/2 and 12 V.
6. Install a jumper wire between relay terminal 86/1 and ground.
7. Test for less than 2 ohms between terminals 30/3 and 87/5. If 2 ohms or greater Replace the cooling fan relay. If less than 2 ohms
8. All OK.

Cooling Fan Motor Test

1. Ignition OFF.
2. Disconnect the harness connector at the R10 Cooling Fan Resistor.
3. Connect a jumper wire between the R10 Cooling Fan Resistor terminal 1 and ground.
4. Connect an appropriately fused jumper wire between a R10 Cooling Fan Resistor terminal listed below and B+. R10 Cooling Fan Resistor low speed terminal 2 R10 Cooling Fan Resistor medium speed terminal 3 R10 Cooling Fan Resistor high speed terminal 4
5. Verify the G10 Cooling Fan Motor operates when voltage is applied to each terminal. The cooling fan does not operate Replace the G10 Cooling Fan Motor. The cooling fan operates
6. All OK.

1. Perform the «Diagnostic System Check - Vehicle»(ref-542476-S03610919532013041600000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-542476-S11988299792013041600000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-542476-S27446858652013041600000) provides an overview of each diagnostic category.

1. The scan tool cooling fan output control operates as follows: Cooling Fan Relay 1 operates the fan at a low speed Cooling Fan Relay 2 operates the fan 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.

Inoperative in All Speeds

1. Ignition OFF, disconnect the harness connector at the G10 Cooling Fan Motor.
2. Verify a test lamp illuminates between the ground circuit terminal C and B+. If the test lamp does not illuminate Ignition OFF, remove the test lamp. Test for less than 2 ohms in the 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 the test lamp illuminates
3. Test or replace the G10 Cooling Fan Motor. Replace the cooling fan fuses if necessary.

Low or High Speed Inoperative

1. Disconnect the following cooling fan relays, ignition ON: KR20C Cooling Fan Low Speed Relay KR20D Cooling Fan High Speed Relay
2. Verify a test lamp illuminates between ground and each of the cooling fan relay B+ circuit terminals listed below: KR20C Cooling Fan Low Speed Relay terminal 30 KR20D Cooling Fan High Speed Relay terminal 30 If the test lamp does not illuminate and the circuit fuse is good Ignition OFF, remove the test lamp. Test for less than 2 ohms in the appropriate relay B+ circuit, 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, disconnect the harness connector at the G10 Cooling Fan Motor. Test for infinite resistance between the appropriate relay controlled output circuit terminal listed below and ground: KR20C Cooling Fan Low Speed Relay terminal 87 KR20D Cooling Fan High Speed Relay terminal 87 If less than infinite resistance, repair the short to ground in the circuit. If infinite resistance, test or replace the G10 Cooling Fan Motor, replace the fuse as necessary. If the test lamp illuminates
3. Ignition OFF, install all of the previously removed KR20 Cooling Fan Relays. Disconnect the harness connector at the G10 Cooling Fan Motor, ignition ON.
4. Command the cooling fan ON at high or low speed as appropriate with a scan tool.
5. Verify a test lamp illuminates between ground and appropriate G10 Cooling Fan Motor circuit terminals listed below: G10 Cooling Fan low speed circuit terminal B G10 Cooling Fan high speed circuit terminal A If the test lamp does not illuminate at each terminal Ignition OFF, remove the test lamp. Disconnect the appropriate relay from the list below: KR20C Cooling Fan Low Speed Relay KR20D Cooling Fan High Speed Relay Test for less than 2 ohms in the relay controlled output circuit, end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, test or replace the relay. If the test lamp illuminate at each terminal
6. Test or replace the G10 Cooling Fan Motor.

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 or greater than the specified range Replace the KR20 Cooling Fan Relay. If within the specified range
4. Test for infinite resistance between the following terminals: 30/3 and 86/1 30/3 and 87/5 30/3 and 85/2 85/2 and 87/5 If less than infinite resistance Replace the KR20 Cooling Fan Relay. If infinite resistance
5. Install a 20 A fused jumper wire between relay terminal 85/2 and 12 V.
6. Install a jumper wire between relay terminal 86/1 and ground.
7. Test for less than 2 ohms between terminals 30/3 and 87/5. If 2 ohms or greater Replace the KR20 Cooling Fan Relay. If less than 2 ohms
8. All OK.

Thermostat Diagnosis

Thermostat Diagnosis

Cooling System Leak Testing

Special Tools

1. EN 471 Adapter
2. EN 6327 A Cooling System Test Adapter

For equivalent regional Tools, refer to Special Tools .

1. Remove the surge tank cap.
2. Check the coolant level. Fill the coolant level to the COLD mark if necessary.
3. Pull the coolant expansion tank from the bracket in the direction of the battery.
4. Attach the coolant system tester with EN 471 adapter and EN 6327 A adapter to the coolant expansion tank.
5. Apply approximately 100 kPa (15 psi) to the cooling system.
6. Check the cooling system for leaks.
7. Remove the cooling system tester. Release the pressure Remove the cooling system tester with EN 471 adapter
8. Install the surge tank cap.