DTC P1660 Cooling Fan Control Circuits. Oldsmobile Aurora 1997

For 1990-2009 cars only

Makes 🢒 Oldsmobile 🢒 1997 🢒 Aurora 🢒 DTC 🢒 DTC P1660 Cooling Fan Control Circuits

Refer to

Coolant Fans/Relays

PCM Power and Grounds
A/C Sensors
Engine Controls Components
OBD II Symbol Description Notice
ESD Notice
for wiring view .

The PCM contains a chip called a Quad Driver Module that provides 4 switchable ground outputs for operating solenoids, relays, telltales, and other devices. Each of these ground outputs has an internal fault line that feeds back to the PCM's microprocessor. When the output is OFF, the quad driver should receive the 12 volts fed to the solenoid, relay, etc. When the output is ON, the ouad driver should receive 0 volt since it is grounding the output. If it receives 0 volt when the output is OFF or 12 volts when the output is ON, it sets the fault line low. DTC P1660 is used to monitor the fault line of the cooling fan control relay output and the starter inhibit output.

Conditions for Setting the DTC

Test Conditions

•	Ignition voltage between 10 and 16 volts.

•	PCM in Closed Loop fuel control.

•	Engine running for at least 10 seconds.

Failure Condition

Fault line is low for 2 seconds.

Action Taken When the DTC Sets

•	The PCM will illuminate the malfunction indicator lamp (MIL) when the diagnostic runs and fails.

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

Conditions for Clearing the MIL/DTC

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

•	A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail.

•	A History DTC will clear after forty consecutive warm-up cycles with no failures of any emission related diagnostic test.

•	Use a scan tool to clear DTCs.

•	Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Clearing Diagnostic Trouble Codes in PCM Description and Operation.

Step

Action

Value(s)

Yes

Was the Powertrain OBD System Check performed?

Go to Step 2

Go to A Powertrain On Board Diagnostic (OBD) System Check

Turn the key ON.
Turn all HVAC controls to OFF.
Using a scan tool select the Output Tests for the Fan Relays.
While checking the Quad Driver 1 display, command All Relays OFF.

Does the display indicate OK?

Go to Step 3

Go to Step 9

While checking the Quad Driver 1 display, command All Relays ON.

Does the display indicate OK?

Go to Step 4

Go to Step 6

Turn the key ON engine OFF.
Command the Starter Inhibit ON.

Does the Quad Driver 1 display indicate OK?

Go to Step 5

Go to Step 20

Is there a cooling fan operation complaint or fault suspected?

Go to Electric Cooling Fan Diagnosis (Functional Check)

Fault not present.

While checking the Quad Driver 1 display, command Fan Relay 1 ON.

Does the display indicate OK?

Go to Step 8

Go to Step 7

Record the fluid life indexes, turn the key to LOCK and wait 30 seconds.
Disconnect PCM connector C2.
Remove fan relay 1 (low speed).
Turn the key ON.
Using DVM J 39200 measure the voltage to ground at PCM connector C2 terminal 32.

Is the voltage the same or less than the value specified?

0.5 volts

Go to Step 27

Go to Step 18

Record the fluid life indexes, turn the key to LOCK and wait 30 seconds.
Disconnect PCM connector C2.
Remove fan relays 2 and 3.
Turn the key ON.
Using DVM J 39200 measure the voltage to ground at PCM connector C2 terminal 33.

Is the voltage the same or less than the value specified?

0.5 volts

Go to Step 27

Go to Step 19

In the scan tool data list note the Passkey Starter display.

Does the display indicate Enabled?

Go to Step 9

Go to Step 21

With All Relays still commanded OFF observe the operation of both cooling fans.

Is either fan operating?

Go to Step 11

Go to Step 12

Record the fluid life indexes, turn the key to LOCK and wait 30 seconds.
Disconnect PCM connector C2.
Turn the key ON.
Using DVM J 39200 measure the voltage to ground at PCM terminal 32.

Is the voltage the same or more than the value specified?

10.0 volts

Go to Step 16

Go to Step 17

Record the fluid life indexes, turn the key to LOCK and wait 30 seconds.
Disconnect PCM connector C2.
Turn the key ON.
Using DVM J 39200 measure the voltage to ground at PCM terminals 32 and 33.

Is the voltage the on both terminals the same or more than the value specified?

10.0 volts

Go to Step 27

Go to Step 13

Was the voltage measured in Step 9 low for both terminals?

Go to Step 15

Go to Step 14

Repair the open circuit or replace the open fan relay for the CKT that measured low in Step 9.

Is the repair complete?

Go to Powertrain Control Module Diagnosis for Verify Repair

Repair the cause of no voltage to both circuits.
Replace the fuse if blown.
Possible causes are:

•	Open in both CKT 335 and CKT 473.

•	Open in CKT 2340 to both relays.

•	Short to ground in CKT 2340 to relays (blown fuse).

•	Shorted fan relay(s) (blown fuse).

•	Short to ground in CKT 2340 to A/C compressor relay (blown fuse).

•	Shorted A/C compressor relay (blown fuse).

Is the repair complete?

Go to Powertrain Control Module Diagnosis for Verify Repair

Repair short to ground in the Cooling Fan High Speed Control circuit.

Is the repair complete?

Go to Powertrain Control Module Diagnosis for Verify Repair

Repair short to ground in the Cooling Fan Low Speed Control circuit.

Is the repair complete?

Go to Powertrain Control Module Diagnosis for Verify Repair

Repair short to voltage in the Cooling Fan Low Speed Control circuit.

Is the repair complete?

Go to Powertrain Control Module Diagnosis for Verify Repair

Repair short to voltage in the Cooling Fan High Speed Control circuit.

Is the repair complete?

Go to Powertrain Control Module Diagnosis for Verify Repair

Record the fluid life indexes, turn the key to OFF and wait 30 seconds.
Disconnect PCM connector C2 and the Passkey module connector.
Turn the key to ON.
Using J 39200 measure the voltage to ground at PCM connector C2 terminal 31.

Is the voltage more than the value specified?

0.5 volts

Go to Step 24

Go to Step 27

Record the fluid life indexes, turn the key to OFF and wait 30 seconds.
Disconnect PCM connector C2.
With the key ON, measure the voltage to ground at PCM connector C2 terminal 31.

Is the voltage the same or more than the value specified?

10.5 volts

Go to Step 27

Go to Step 22

Turn the key OFF.
Disconnect the Passkey module.
Measure the resistance to ground at PCM connector C2 terminal 31.
Is the resistance the same or more than the value specified?

10K ohms

Go to Step 23

Go to Step 25

Measure the resistance between PCM connector C2 terminal 31 and the Passkey module terminal A7.

Is the resistance less then the value specified?

5 ohms

Fault is in Passkey system. Go to Section 9, Theft Deterrent Systems.

Go to Step 26

Repair short to voltage on the Starter Inhibit Output circuit.

Is the repair complete?

Go to Powertrain Control Module Diagnosis for Verify Repair

Repair the short to ground on the Starter Inhibit Output circuit.

Is the repair complete?

Go to Powertrain Control Module Diagnosis for Verify Repair

Repair the open in the Starter Inhibit Output circuit.

Is the repair complete?

Go to Powertrain Control Module Diagnosis for Verify Repair

Check terminal contact at the PCM.
Repair terminal contact if needed.

Was terminal contact repaired?

Go to Powertrain Control Module Diagnosis for Verify Repair

Go to Step 28

Replace the PCM. Refer to PCM Replacement/Programming .

Is the replacement complete?

Go to Powertrain Control Module Diagnosis for Verify Repair

Coolant Fans/Relays

Circuit Description

Conditions for Setting the DTC

Test Conditions

Failure Condition

Action Taken When the DTC Sets

Conditions for Clearing the MIL/DTC