DTC P0481Cooling Fan Relay 2 Control Circuit. Oldsmobile Alero 2000

For 1990-2009 cars only

Makes 🢒 Oldsmobile 🢒 2000 🢒 Alero 🢒 Engine 🢒 Engine Controls - 2.4L 🢒 DTC P0481Cooling Fan Relay 2 Control Circuit

Refer to

Power, Ground, and Cooling Fans

Engine Controls Components
Engine Cooling Fan Description - Electric
Fuel Tank Module
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Power Distribution Schematics
Power Distribution Schematics
Ground Distribution Schematics
Ground Distribution Schematics
.

Circuit Description

The Body Control Module (BCM) request the cooling fans be turned on by sending a Class 2 message to the Powertrain Control Module (PCM). The PCM enables the cooling fan relay 1 by providing a ground path. The PCM enables the cooling fan relay 2 and the mode control together by providing a ground path. The left and right cooling fans are connected in series. This enables both fans to operate on low speed when relay 1 is energized. When all 3 relays are energized, both fans will operate at high speed. When the PCM determines that certain DTCs are set, the PCM will enable the cooling fans.

Conditions for Running the DTC

•	The engine is running.

•	The battery voltage is more than 9.5 volts.

Conditions for Setting the DTC

•	The PCM detects that the commanded state of the driver and the actual state of the control circuit do not match.

•	The condition must be present for a minimum of 6 seconds.

Action Taken When the DTC Sets

•	The PCM will illuminate the malfunction indicator lamp (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with the fault active.

•	The PCM will record the operating conditions at the time during which the diagnostic fails. This information will store in the Freeze Frame and Failure Records.

Conditions for Clearing the MIL/DTC

•	The PCM will turn the MIL off after 3 consecutive drive trips that the diagnostic runs and does not fail.

•	A History DTC will clear after 40 consecutive warm-up cycles if no failures are report by this diagnostic or any other emission related diagnostic.

•	Use a scan tool to clear the DTCs.

Diagnostic Aids

The Freeze Frame and Failure Records may aid in locating an intermittent condition. If the DTC cannot be duplicated, the information included in the Freeze Frame and Failure Records can be useful in determining how many miles since the DTC set. You can also use the Fail Counter and the Pass Counter in order to determine how many ignition cycles during which the diagnostic reported a pass or a fail. Operate the vehicle within the same Freeze Frame conditions that were noted. This will isolate when the DTC failed.

Test Description

The numbers below refer to step numbers on the diagnostic table.

Listen for an audible click when the fan control relay 2 operates. Be sure that both the on and off states are commanded.

This step detects a partially shorted coil which would cause an excessive current flow. Allow the coil to warm up by leaving the circuit energized for 2 minutes. When warm, the coil may open or short.

It is important to identify and test the fan control relay 2 coil terminals to avoid improper diagnosis.

The replacement PCM must be programmed and the Crankshaft Position System Variation Learn procedure must be performed.

DTC P0481 Fan Control Relay 2 Control Circuit

Step

Action

Values

Yes

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

Remove the mode control relay.
Turn on the ignition, leaving the engine off.
Use a scan tool in order to command the fan control relay 2 on and off.

Does the fan control relay 2 turn on and off with each command?

Go to Step 3

Go to Step 5

Turn off the ignition.
Disconnect the PCM connector containing the control circuit for the fan control relay 2 .
Turn on the ignition, leaving the engine off.
Use a DMM set to the 10 Amp scale in order to measure the current between the relay 2 control circuit and ground at the PCM connector for 2 minutes.

Is the current draw less than the specified value, but not zero?

0.75 A

Go to Step 8

Go to Step 4

Turn off the ignition.
Remove the fan control relay 2.
With the DMM still installed, switch the setting on the DMM to ohms.

Does the DMM display infinite resistance?

Go to Step 16

Go to Step 14

Turn off the ignition.
Remove the fan control relay 2.
Connect a test lamp between the following circuits in the connector:

•	The control circuit

•	The battery feed circuit

Turn on the ignition, leaving the engine off.
Command the fan control relay 2 on and off with the scan tool.

Does the test lamp turn on and off with each command?

Go to Step 12

Go to Step 6

Connect a test lamp to ground.
Probe the battery feed circuit in the relay 2 connector.

Does the test lamp illuminate?

Go to Step 7

Go to Step 15

Turn off the ignition.
Install the fan control relay 2.
Disconnect the PCM connector containing the control circuit for the fan control relay 2 .
Turn on the ignition, leaving the engine off.
Connect a fused jumper wire to ground.
Probe the relay 2 control circuit at the PCM connector. Probe and release several times.

Does the relay turn on and off?

Go to Step 13

Go to Step 14

Turn off the ignition.
Reinstall the mode control relay.
Remove the fan control relay 2.
Connect a fused jumper between the relay 2 control circuit and ground at the PCM connector.
Turn on the ignition, leaving the engine off.

Does the relay turn on?

Go to Step 9

Go to Step 10

Use a DMM set to the 10 Amp scale in order to measure the current between the control circuit of the mode control relay and ground at the PCM connector for 2 minutes.

Is the current draw less than the specified value, but not 0?

0.75 A

Go to Diagnostic Aids

Go to Step 16

Turn off the ignition.
Remove the mode control relay.
Connect a test lamp between the coil terminals of the mode control relay at the connector.
Turn on the ignition, leaving the engine off.
Connect a fused jumper wire between the control circuit of the mode control relay and ground at the PCM connector.

Does the test lamp illuminate?

Go to Step 12

Go to Step 11

Connect a test lamp to ground.
Probe the battery feed circuit in the mode control relay connector.

Does the test lamp illuminate?

Go to Step 14

Go to Step 15

Turn off the ignition.
Inspect for poor connections at the affected relay. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 18

Go to Step 16

Turn off the ignition.
Inspect for poor connections at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 18

Go to Step 17

Turn off the ignition.
Test the control circuit of the fan control relay for the following conditions:

•	A short to ground

•	A short to voltage

•

An open

If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 18

Turn off the ignition.
Test the battery feed circuit of the fan control relay 2 for the following conditions:

•	A short to ground

•

An open

If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 18

Turn off the ignition.
Replace the relay. Refer to Air Conditioning (A/C) Compressor and Cooling Fan Relays Replacement .

Did you complete the repair?

Go to Step 18

Important:: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming .

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the repair?

Go to Step 18

Use a scan tool to clear the DTCs.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK