• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
• | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
• | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
The engine control module (ECM) commands the fans ON in either high speed, medium speed, or low speed, depending on cooling requirements.
In low speed operation, the ECM applies ground to the coil side of the following relays with the cooling fan relay 1 control circuit:
• | Cooling Fan Left Low Speed Relay |
• | Cooling Fan Right Low Speed Relay |
• | Cooling Fan Speed Control Relay |
This energizes the relay coils. The low speed cooling fan relays supply power to the appropriate cooling fan motor through an internal fan resistor. The fan speed control relay contacts close and supply a direct ground path for the left cooling fan motor. The right cooling fan motor is connected to a dedicated ground. This results in both fans operating at low speed.
In medium speed operation, the ECM commands the low speed fan relays, and the speed control relay off. The ECM simultaneously commands both of the cooling fan high speed relays on with the cooling fan relay 2 control circuit. The cooling fan motors are supplied power directly from the cooling fan high speed relays. The right cooling fan is connected to a dedicated ground, and operates at high speed. The left cooling fan is supplied a ground through the right cooling fan resistor and fan motor, which is connected to the de-energized cooling fan speed control relay. This results in the right cooling fan operating at a reduced speed.
In high speed operation, the ECM applies a ground to the coil side of all five cooling fan relays. When energized, the high speed relays apply voltage directly to the cooling fans through the switch side of the relays. The energized cooling fan speed control relay provides a direct ground circuit for the left cooling fan. This arrangement allows each fan to receive full voltage and operate at high speed.
Cooling Fan Description and Operation
Control Module References for scan tool information
⇒ | If any of the above DTCs are set refer to DTC P0480, P0481, P0691, P0692, P0693, or P0694. |
⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
Note: The following test must performed on all cooling fan relays.
⇒ | If the test lamp does not illuminate, test the relay switch B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the relay switch B+ circuit fuse is open, test the relay controlled output circuit for a short to ground. If the circuit tests normal, test or replace the appropriate cooling fan motor. |
Note: The following test must be performed on both cooling fan low speed relays.
⇒ | If the fan does not activate, test the following conditions and repair as necessary. |
• | Relay controlled output circuit for a short to ground or an open/high resistance |
• | Open cooling fan resistor |
• | Open circuit between the G10L left cooling fan relay and the KR20E cooling fan speed relay |
• | Fan ground circuit for an open/high resistance |
• | Cooling fan motor |
Note: The following test must be performed on both cooling fan high speed relays.
⇒ | If the fan does not activate, test the relay controlled output circuit for a short to ground or an open/high resistance. |
⇒ | If the left cooling fan does not activate test the relay controlled output circuit for an open/high resistance. |
⇒ | If the not within the specified range, replace the relay. |
• | 2 and 6 |
• | 2 and 8 |
• | 2 and 4 |
• | 4 and 8 |
⇒ | If not the specified range, replace the relay. |
⇒ | If greater than the specified range, replace the relay. |
Note: This step is only for the KR20E cooling fan speed control relay.
⇒ | If greater than the specified range, replace the relay. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
• | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
• | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
The engine cooling fan system is composed of one fan, 5 relays, the engine control module (ECM), and the associated wiring. The fan assembly includes two resistors, which enable the fan to operate at 3 speeds.
In low speed operation, the ECM provides ground to ECM terminal X2 46. The Cooling Fan Relay activates and provides ground to the coils of the Cooling Fan Medium Speed 2 Relay and the Cooling Fan Speed Control Relay. The Cooling Fan Speed Control Relay activates and provides power to the coil of the Cooling Fan High Speed Relay. The Cooling Fan High Speed Relay remains inactive because ECM terminal X2 45 is not grounded. The Cooling Fan Medium Speed 2 Relay provides power to the cooling fan motor through cooling fan terminal 2 and the internal fan resistor.
In medium speed operation, the ECM provides ground to ECM terminal X2 45. The Cooling Fan High Speed Relay remains inactive because power is not provided to the coil from the Cooling Fan Speed Control Relay. The Cooling Fan Medium Speed 1 Relay activates and provides power to the cooling fan motor through cooling fan terminal 3 and the internal fan resistor.
In high speed operation, the ECM provides ground to ECM terminals X2 45 and X2 46. As previously described, power is now provided to both cooling fan terminals 2 and 3. In addition, power and ground are now provided to the coil of the Cooling Fan High Speed Relay. The Cooling Fan High Speed Relay activates and provides power to the cooling fan motor through cooling fan terminal 4.
Cooling Fan Description and Operation
Control Module References for scan tool information
⇒ | If any cooling system DTCs are set, repair the DTC first. Refer to DTC P0480, P0481, P0691, P0692, P0693, or P0694. |
⇒ | If the fan does not operate correctly, go to low speed operation malfunction. |
⇒ | If the fan does not operate correctly, go to medium speed operation malfunction. |
⇒ | If the fan does not operate correctly, go to high speed operation malfunction. |
Note: The Circuit/System Verification must be performed before the Circuit/System Testing or misdiagnosis may result.
• | KR20B Cooling Fan Medium Speed 2 Relay |
• | KR20E Cooling Fan Speed Control Relay |
• | KR20F Cooling Fan Relay |
⇒ | If greater than the specified range, test the output circuit for an open/high resistance. |
⇒ | If the test lamp does not illuminate, test the relay coil ignition circuit for an open/high resistance. |
⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the relay controlled output circuit terminals of the relay connectors listed below for a short to ground: |
• | KR20A Cooling Fan Medium Speed 1 Relay |
• | KR20B Cooling Fan Medium Speed 2 Relay |
⇒ | If the test lamp does not illuminate, test the relay switch ignition circuit terminal at the KR20F Cooling Fan Relay connector for a short to ground or an open/high resistance. |
⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
⇒ | If the cooling fan does not activate at low speed, test the output circuit for an open/high resistance. If the circuit tests normal, test or replace the cooling fan. |
• | KR20F Cooling Fan Relay |
• | KR20B Cooling Fan Medium Speed 2 Relay |
⇒ | If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. |
⇒ | If the test lamp does not illuminate, test the B+ circuit for an open/high resistance. |
⇒ | If the cooling fan does not activate at medium speed, test the output circuit for an open/high resistance. If the circuit tests normal, test or replace the G10 Engine Cooling Fan. |
⇒ | If more than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, test the KR20E Cooling Fan Speed Control Relay for correct operation. If the relay tests normal, replace the K20 ECM. |
• | KR20D Cooling Fan High Speed Relay |
• | KR20E Cooling Fan Speed Control Relay |
⇒ | If the test lamp does not illuminate, test the ignition circuit for an open/high resistance. |
⇒ | If the test lamp does not illuminate, test the ignition circuit for an open/high resistance. |
⇒ | If the test lamp does not illuminate, test the ignition circuit terminal for an open/high resistance. |
⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the relay controlled output circuit for a short to ground. If the circuit tests normal, test or replace the G10 Engine Cooling Fan. |
⇒ | If the cooling fan does not activate at high speed, test the output circuit for an open/high resistance. If the circuit tests normal, test or replace the G10 Engine Cooling Fan. |
• | KR20E Cooling Fan Speed Control Relay |
• | KR20D Cooling Fan High Speed Relay |
⇒ | If the resistance is not within the specified range, replace the relay. |
• | 30 and 86 |
• | 30 and 87 |
• | 30 and 85 |
• | 85 and 87 |
⇒ | If not the specified range, replace the relay. |
⇒ | If greater than the specified range, replace the relay. |
⇒ | If greater than the specified range, replace the relay. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
• | Engine Cooling Fan Replacement 37302 |
• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
• | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
• | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Circuit | Short to Ground | High Resistance | Open | Short to voltage | Signal Performance |
---|---|---|---|---|---|
Relay Coil Ignition Circuit | P0691 00 | P0691 00 | P0480 00 | -- | -- |
Relay Switch B+ Circuit | 1 | 1 | 1 | -- | -- |
Relay Coil Control Circuit | P0691 00 | P0691 00 | P0480 00 | P0692 00 | -- |
Relay Controlled Output Circuit | 1 | 1 | 1 | 2 | -- |
|
Circuit | Short to Ground | High Resistance | Open | Short to voltage | Signal Performance |
---|---|---|---|---|---|
Relay Coil Ignition Circuit | P0693 00 | P0693 00 | P0481 00 | -- | -- |
Relay Switch B+ Circuit | 1 | 1 | 1 | -- | -- |
Relay Coil Control Circuit | P0693 00 | P0693 00 | P0481 00 | P0694 00 | -- |
Relay Controlled Output Circuit | 1 | 1 | 1 | 2 | -- |
|
Circuit | Short to Ground | High Resistance | Open | Short to voltage | Signal Performance |
---|---|---|---|---|---|
Relay Coil Ignition Circuit | P0695 00 | P0695 00 | P0482 00 | -- | -- |
Relay Switch B+ Circuit | 1 | 1 | 1 | -- | -- |
Relay Coil Control Circuit | P0695 00 | P0695 00 | P0482 00 | P0696 00 | -- |
Relay Controlled Output Circuit | 1 | 1 | 1 | 2 | -- |
|
The engine control module (ECM) commands the fans ON in either high speed, medium speed, or low speed, depending on cooling requirements.
In low speed operation, the ECM applies ground to the coil side of the following relays with the cooling fan relay 1 control circuit:
• | Cooling Fan Left Low Speed Relay |
• | Cooling Fan Right Low Speed Relay |
• | Cooling Fan Speed Control Relay |
This energizes the relay coils. The low speed cooling fan relays supply power to the appropriate cooling fan motor through an internal fan resistor. The fan speed control relay contacts close and supply a direct ground path for the left cooling fan motor. The right cooling fan motor is connected to a dedicated ground. This results in both fans operating at low speed.
In medium speed operation, the ECM commands the low speed fan relays, and the speed control relay off. The ECM simultaneously commands both of the cooling fan high speed relays on with the cooling fan relay 2 control circuit. The cooling fan motors are supplied power directly from the cooling fan high speed relays. The right cooling fan is connected to a dedicated ground, and operates at high speed. The left cooling fan is supplied a ground through the right cooling fan resistor and fan motor, which is connected to the de-energized cooling fan speed control relay. This results in the right cooling fan operating at a reduced speed.
In high speed operation, the ECM applies a ground to the coil side of all five cooling fan relays. When energized, the high speed relays apply voltage directly to the cooling fans through the switch side of the relays. The energized cooling fan speed control relay provides a direct ground circuit for the left cooling fan. This arrangement allows each fan to receive full voltage and operate at high speed.
Cooling Fan Description and Operation
⇒ | If any of the above DTCs are set refer to Diagnostic Trouble Code (DTC) List - Vehicle |
⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
Note: The following test must performed on all cooling fan relays.
⇒ | If the test lamp does not illuminate, test the relay switch B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the relay switch B+ circuit fuse is open, test the relay controlled output circuit for a short to ground. If the circuit tests normal, test or replace the appropriate cooling fan motor. |
Note: The following test must be performed on both cooling fan low speed relays.
⇒ | If the fan does not activate, test the following conditions and repair as necessary. |
• | Relay controlled output circuit for a short to ground or an open/high resistance |
• | Open cooling fan resistor |
• | Open circuit between the G10L Cooling Fan Motor - Left terminal 3 and the KR20E Cooling Fan Speed Control Relay terminal 2 |
• | Fan ground circuit for an open/high resistance |
• | Cooling fan motor |
Note: The following test must be performed on both cooling fan high speed relays.
⇒ | If the fan does not activate, test the relay controlled output circuit for a short to ground or an open/high resistance. |
⇒ | If the left cooling fan does not activate test the relay controlled output circuit for an open/high resistance. |
⇒ | If the resistance is not within the specified range, replace the relay. |
• | 2 and 6 |
• | 2 and 8 |
• | 2 and 4 |
• | 4 and 8 |
⇒ | If not the specified value, replace the relay. |
⇒ | If greater than the specified range, replace the relay. |
Note: This step is only for the KR20E cooling fan speed control relay.
⇒ | If greater than the specified range, replace the relay. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
• | LINK 22835 |
• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
• | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
• | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
The engine control module (ECM) commands the fans ON in either high speed, medium speed, or low speed, depending on cooling requirements.
In low speed operation, the ECM applies ground to the coil side of the following relays with the cooling fan relay 1 control circuit:
• | Cooling Fan Left Low Speed Relay |
• | Cooling Fan Right Low Speed Relay |
• | Cooling Fan Speed Control Relay |
This energizes the relay coils. The low speed cooling fan relays supply power to the appropriate cooling fan motor through an internal fan resistor. The fan speed control relay contacts close and supply a direct ground path for the left cooling fan motor. The right cooling fan motor is connected to a dedicated ground. This results in both fans operating at low speed.
In medium speed operation, the ECM commands the low speed fan relays, and the speed control relay off. The ECM simultaneously commands both of the cooling fan high speed relays on with the cooling fan relay 2 control circuit. The cooling fan motors are supplied power directly from the cooling fan high speed relays. The right cooling fan is connected to a dedicated ground, and operates at high speed. The left cooling fan is supplied a ground through the right cooling fan resistor and fan motor, which is connected to the de-energized cooling fan speed control relay. This results in the left cooling fan operating at a reduced speed.
In high speed operation, the ECM applies a ground to the coil side of all five cooling fan relays. When energized, the high speed relays apply voltage directly to the cooling fans through the switch side of the relays. The energized cooling fan speed control relay provides a direct ground circuit for the left cooling fan. This arrangement allows each fan to receive full voltage and operate at high speed.
Cooling Fan Description and Operation
Control Module References for scan tool information
⇒ | If any of the above DTCs are set refer to DTC P0480, P0481, P0691, P0692, P0693, or P0694. |
⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
Note: The following test must performed on all cooling fan relays.
⇒ | If the test lamp does not illuminate, test the relay switch B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the relay switch B+ circuit fuse is open, test the relay controlled output circuit for a short to ground. If the circuit tests normal, test or replace the appropriate cooling fan motor. |
Note: The following test must be performed on both cooling fan low speed relays.
⇒ | If the fan does not activate, test the following conditions and repair as necessary. |
• | Relay controlled output circuit for a short to ground or an open/high resistance |
• | Open cooling fan resistor |
• | Open circuit between the G10L left cooling fan relay and the KR20E cooling fan speed relay |
• | Fan ground circuit for an open/high resistance |
• | Cooling fan motor |
Note: The following test must be performed on both cooling fan high speed relays.
⇒ | If the fan does not activate, test the relay controlled output circuit for a short to ground or an open/high resistance. |
⇒ | If the left cooling fan does not activate test the relay controlled output circuit for an open/high resistance. |
⇒ | If the not within the specified range, replace the relay. |
• | 2 and 6 |
• | 2 and 8 |
• | 2 and 4 |
• | 4 and 8 |
⇒ | If not the specified range, replace the relay. |
⇒ | If greater than the specified range, replace the relay. |
Note: This step is only for the KR20E cooling fan speed control relay.
⇒ | If greater than the specified range, replace the relay. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.