DTC P0480 Cooling Fan Relay 1 Control
Circuit
For schematic details
refer to Engine
Cooling Fan Circuit .
The cooling fan system
in this vehicle provides for two separate modes of operation. These are the low
speed fan and the high speed fan operating modes. The low speed mode operates
both fans at half speed by using a series circuit configuration. The high speed
mode operates both fans at full speed by using a parallel circuit
configuration. These two operating modes are accomplished using 3 fan control
relays.
This system which uses
three relays to control two fan motors appears complicated. To aid in better
understanding this system it is suggested to follow the circuits in the
schematic as you read the description. This will aid in understanding the two
distinct modes of operating the relays and coolant fans.
Low speed fan operation
is established when the PCM commands Fan Relay #1 ON by grounding circuit 335
with an internal driver (relays #2 and #3 are left OFF). This closes the relay
switch and allows current to flow from the battery, through the switch contacts
on circuit 409 to the Left Hand cooling fan. Current flow continues out of the
fan motor on circuit 532 to relay #3. The unenergized
relay #3 switch contacts allow current to flow to circuit 504. This provides
power to the Right Hand cooling fan motor. The low side of the RH cooling fan
completes the circuit to ground on circuit 150. This circuit is a series
circuit which allows half speed operation for each fan since each fan motor
will use half of the supplied battery power.
High speed operation is
established when all three relays are energized. Relays #2
and #3 share the same control circuit to the PCM. This is circuit 473.
As in the low speed mode, Relay #1 supplies current flow to the LH cooling fan
on circuit 409. Current flow continues through the motor on circuit 532 to
relay #3 which is now energized. The switch has now provided a path for current
to flow through circuit 150 directly to ground. This circuit now only has the
LH fan motor to power and allows it to run at full speed. Relay #2 is also
energized and provides current flow on circuit 504 to the RH cooling fan. This
fan now has its own dedicated circuit and will operate at full speed. This mode
is operating as a parallel circuit.
Conditions
for Running the DTC
Conditions
for Setting the DTC
Action
Taken When the DTC Sets
Conditions
for Clearing the MIL/DTC
Using Freeze Frame
and/or Failure Records data may aid in locating an intermittent condition. If
you cannot duplicate the DTC, the information included in the Freeze Frame
and/or Failure Records data can aid in determining how many miles since the DTC
set. The Fail Counter and Pass Counter can also aid determining how many
ignition cycles the diagnostic reported a pass and/or a fail. Operate the
vehicle within the same freeze frame conditions (RPM, load, vehicle speed,
temperature etc.) that you observed. This will isolate when the DTC failed.
For an intermittent,
refer to Symptoms
.
The numbers below refer
to the step numbers on the diagnostic table.
|
Step |
Action |
Value(s) |
Yes |
No |
|
Did
you perform the Powertrain On-Board Diagnostic
(OBD) System Check? |
-- |
|||
Does
the relay turn ON and OFF when commanded? |
-- |
|||
Important If
the DMM goes to 0 Amps during the current draw test, replace the relay.
Does
the current draw measure less than the specified value shown (but not 0)? |
0.75A |
Go to Diagnostic Aids |
||
|
Important For underhood
electrical center relay terminal identification, refer to Electrical
Center Identification Views in Wiring Systems.
Does
the DMM display infinite resistance? |
-- |
|||
|
Important For underhood
electrical center relay terminal identification, refer to Electrical
Center Identification Views in Wiring Systems.
Does
the test lamp turn ON and OFF with each command? |
-- |
|||
|
Probe
the FC relay 1 B+ supply circuits at the underhood
electrical center with the test lamp J 34142-B
connected to ground. Is the test lamp illuminated? |
-- |
|||
Does
the relay turn ON when the circuit is grounded and OFF when the circuit is
opened? |
-- |
|||
Did
you find and correct the condition? |
-- |
|||
Did
you find and correct the condition? |
-- |
|||
|
Repair
the relay control circuit. Refer to Wiring
Repairs in Wiring Systems. Is the action complete? |
-- |
-- |
||
|
Repair
the relay B+ supply circuit. Refer to Wiring
Repairs in Wiring Systems. Is the action complete? |
-- |
-- |
||
|
Replace
the relay. Refer to Cooling
Fan Relay Replacement in Engine Cooling. Is the replacement complete? |
-- |
-- |
||
|
Important: Program the replacement
PCM. Refer to PCM
Replacement/Programming . Replace
the PCM. Is the action complete? |
-- |
-- |
||
Does
the scan tool indicate that this test passed? |
-- |
|||
|
Select
the Capture Info option and the Review Info option using the scan tool. Does
the scan tool display any DTCs that you have not diagnosed? |
-- |
Go to the applicable
DTC table |
System OK |