DTC P0480 or P0481 - 2H0, LDE, LDD, LLU, or LUJ
Diagnostic Instructions
DTC Descriptors
DTC P0480 00: Cooling Fan Relay 1 Control
Circuit Malfunction
DTC P0481 00: Cooling Fan Relay 2 Control
Circuit Malfunction
Diagnostic Fault Information
Circuit
|
Short to Ground
|
Open/High Resistance
|
Short to Voltage
|
Signal Performance
|
Relay Coil Ignition
|
P0480 00, P0481 00
|
P0480 00, P0481 00
|
-
|
-
|
Relay Switch Ignition
|
1
|
1
|
-
|
-
|
Fan Low Control
|
P0480 00
|
P0480 00
|
P0480 00
|
-
|
Fan High or Fan Control
|
P0481 00
|
P0481 00
|
P0481 00
|
-
|
Relay Output Control
|
1
|
1
|
2
|
-
|
1. Fans Inoperative Without a DTC.
2. Fans Always ON Without a DTC.
|
Circuit/System Description
The engine cooling fan system is composed of one fan,
3 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.
Low Speed
In low speed operation, the ECM provides ground from ECM
terminal 44 X1. The Cooling Fan Low Speed Relay activates
and provides power to the cooling fan motor through cooling fan
motor terminal 3 and the internal fan resistor.
Medium Speed
In medium speed operation, the ECM provides ground from ECM
terminal 15 X1. The Cooling Fan Medium Speed 1 Relay
activates and provides power to the cooling fan motor through
cooling fan motor terminal 2 and the internal fan
resistor.
High Speed
In high speed operation, the ECM provides ground to ECM
terminals 15 X1 and 44 X1. 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.
Conditions for Running the DTC
• |
The ignition voltage is between 11-18 V. |
• |
The engine speed is greater 400 RPM. |
• |
These DTCs run continuously once the above
conditions are met. |
Conditions for Setting the DTC
The ECM detects that the commanded state of the driver and the
actual state of the control circuit do not match for greater than
2 s.
Action Taken When the DTC Sets
DTCs P0480 00 and P0481 00 are Type B DTCs.
Conditions for Clearing the DTC
DTCs P0480 00 and P0481 00 are Type B DTCs.
Reference Information
Schematic Reference
Engine Controls Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Cooling System Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- Ignition ON, command the appropriate
KR20C Cooling Fan Low Speed Relay, KR20A Cooling Fan
Medium Speed 1 Relay and KR20D Cooling Fan High Speed
Relay ON and OFF with a scan tool. You should hear the relay click
when commanded ON and OFF.
- Operate the vehicle within the conditions for running
the DTC to verify the DTC does not reset. You may also operate the
vehicle within the conditions that you observed from the freeze
frame/failure records data.
Circuit/System Testing
- Ignition OFF, disconnect the relays listed below:
• |
KR20A Cooling Fan Medium Speed 1 Relay |
• |
KR20C Cooling Fan Low Speed Relay |
• |
KR20D Cooling Fan High Speed Relay |
- Ignition ON, verify that a test lamp illuminates
between the circuit terminals listed below and ground.
• |
KR20A Cooling Fan Medium Speed 1 Relay
ignition circuit terminal 86 |
• |
KR20C Cooling Fan Low Speed Relay ignition
circuit terminal 86 |
• |
KR20D Cooling Fan High Speed Relay ignition
circuit terminal 86 |
⇒ |
If the test lamp does not illuminate, replace the
X50A Fuse Block - Underbonnet. |
- Verify that a test lamp does not illuminate between
the circuit terminals listed below and ground.
• |
KR20A Cooling Fan Medium Speed 1 Relay
control circuit terminal 85 |
• |
KR20C Cooling Fan Low Speed Relay control
circuit terminal 85 |
⇒ |
If the test lamp illuminates, test the relay coil
control circuit for a short to voltage. If the circuit tests
normal, replace the K20 Engine Control Module. |
- Ignition OFF, disconnect the harness connector X1 at
the K20 Engine Control Module. Test for infinite resistance
between the relay coil control circuit terminals listed below and
ground.
• |
KR20A Cooling Fan Medium Speed 1 Relay
control terminal 85 |
• |
KR20C Cooling Fan Low Speed Relay control
terminal 85 |
⇒ |
If less than the specified value, test the relay
coil control circuit for a short to ground. If the circuit tests
normal, replace the X50A Fuse Block - Underhood. |
- Test for less than 5 Ω between control circuit
terminals listed below.
• |
KR20A Cooling Fan Medium Speed 1 Relay
control terminal 85 and K20 Engine Control Module
terminal 15 X1. |
• |
KR20C Cooling Fan Low Speed Relay control
terminal 85 and K20 Engine Control Module
terminal 44 X1. |
• |
KR20D Cooling Fan High Speed Relay ignition
circuit terminal 85 and K20 Engine Control Module
terminal 15 X1. |
- Connect the KR20C Cooling Fan Low Speed Relay and
the harness connector X1 at the K20 Engine Control
Module.
- Ignition ON, command the Cooling Fan Relay 1 ON
and OFF with a scan tool and verify the DTC does not reset.
⇒ |
If the DTC resets, test or replace the
KR20C Cooling Fan Low Speed Relay and verify the DTC does not
reset. If the DTC resets, replace the K20 Engine Control
Module. |
- Connect the KR20A Cooling Fan Medium Speed 1
Relay.
- Command the Cooling Fan Relays 2 and 3 ON and OFF with
a scan tool and verify the DTC does not reset.
⇒ |
If the DTC resets, test or replace the
KR20A Cooling Fan Medium Speed 1 Relay and verify the DTC
does not reset. If the DTC resets, replace the K20 Engine
Control Module. |
- If all circuits test normal, test or replace
KR20D Cooling Fan High Speed Relay.
Component Testing
Dynamic Test
- Ignition OFF, disconnect the applicable relay.
- Test for 70-110 Ω between terminals 85 and
86 of the relay.
⇒ |
If the resistance is not within the specified
range, replace the relay. |
- Test for infinite resistance between the following
terminals:
⇒ |
If not the specified value, replace the
relay. |
- Install a 20 A fused jumper wire between relay
terminal 85 and 12 V. Install a jumper wire between relay
terminal 86 and ground. Test for less than 2 Ω between
terminals 30 and 87.
⇒ |
If greater than the specified range, replace the
relay. |
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic
procedure.
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