Hi, my 2002 dodge grand caravan sport 3.3 v6 is showing check engine light.
Code from key dance is 1491 which indicates rad fan relay circuit
problem, FANS DO NOT RUN. According to manual it could be relay,
wiring or PCM.
I am attaching an image with all wires going to relay circuit and with
all the voltage on them. fans do run but draw 16 amp when I jump
the circuit to them.
I changed the relay and disconnected the battery at same time.
when i started the van again, code 1491 disappeared . when i turned
switch off in 5 seconds and restarted van, code 1491 came back again.

there are four wires as in image,
Orange wire has 12 volts, Fuse is ok, when in Disconnect fuse, no voltage
on red wire. when i short this wire to light blue wire, fans run, resistance
between orange wire and battery positive terminal is less than 1 ohm.


light Blue wire goes to fans,

Black -green wire goes to lower connector of PCM, has ground all the
time, with resistance between this wire and PCM connector is less than
5 ohm. FAN do not run when i short this wire to ground.

Blue violet wire, has 12 volt all the time, even when switch is off, fan
run when i short this wire to ground, i could trace it to IPM where
resistance is less than 5 ohms. IF SWITCH IS OFF, AND I SHORT THIS
WIRE TO GROUND, FAN STILL RUN.

I WAS EXPECTING PCM WIRE, BLACK GREEN TO HAVE 12 VOLT ALL THE
TIME, AND GROUND WITH AC RUNNING,
AM I TRACING BLUE VIOLET WIRE WRONG, ANY CIRCUIT DIAGRAM MIGHT
HELP.

 

WELL, NO BODY SUGGESTED ANYTHING BUT I FOUND MY SOLUTION. IT WAS AN OPEN CIRCUIT BETWEEN IPM C3 CONNECTOR (18) AND PCM (73).
WHAT WAS HELPFUL, WAS AN ANSWER FROM ALLEXPERTS.COM BY ROLAND.

SO THAT BLUE-VIOLET WIRE IS THE SIGNAL FROM PCM. WHEN I SHORTED IT TO GROUND AT PCM, FAN DID NOT RUN BUT THEY DO RUN WHEN I SHORT THAT WIRE TO GROUND JUST BEFORE ENTERING RELAY. THE RESISTANCE BETWEEN RELAY BLUE VIOLET WIRE AND PCM CONNECTOR 73, BROWN-VIOLET WIRE IS INFINITE. FINALLY I LOCATED INFINITE RESISTANCE BETWEEN PCM-73 AND IPM-C3-18 . SO I CUT THOSE WIRES AND CONNECTED THEM WITH AN EXTERNAL WIRE, AND THEN
PEACE ! EVERYTHING IS WORKING, EVEN THE OLD RELAY, NO ENGINE LIGHT, JUST p1684, WHICH IS DUE TO LOSS OF POWER IN PREVIOUS 50 CYCLES.
I AM ATTACHING SOME MANUAL IMAGES WHICH WILL BE HELPFUL FOR SOMEONE WHO ENCOUNTERS THIS IN FUTURE .
THANKS.

 

here are attached files

 

Thats great. Can you copy and paste that into the tizzy and other DIY sticky?

 

Symptom:
P1491-RAD FAN CONTROL RELAY CIRCUIT
When Monitored and Set Condition:
P1491-RAD FAN CONTROL RELAY CIRCUIT
When Monitored: With the ignition on. Battery voltage greater than 10 volts.
Set Condition: An open or shorted circuit is detected in the radiator fan relay control
circuit.
POSSIBLE CAUSES
RADIATOR FAN RELAY INTERMITTENT OPERATION
INTERMITTENT CONDITION
GROUND CIRCUIT
FUSED B+ OUTPUT CIRCUIT
POWERTRAIN CONTROL MODULE
RADIATOR FAN RELAY CONTROL CIRCUIT SHORT TO GROUND
RADIATOR FAN RELAY CONTROL CIRCUIT OPEN (IPM)
RADIATOR FAN RELAY CONTROL CIRCUIT OPEN (PCM)
RADIATOR FAN RELAY CONTROL CIRCUIT SHORTED TO GROUND (IPM)
RADIATOR FAN RELAY CONTROL CIRCUIT SHORT TO GROUND (PCM)
INTELLIGENT POWER MODULE (OPEN)
INTELLIGENT POWER MODULE (SHORTED)
TEST ACTION APPLICABILITY
1 Turn the ignition on.
With the DRBIIIt, actuate the Radiator Fan Relay.
Are both Radiator Fan operating?

Yes ! Go To 2
No ! Go To 4
2 Turn the ignition on.
With the DRBIIIt, actuate the Radiator Fan Relay.
Wiggle the wiring harness from the Radiator Fan Relay to the PCM while the relay
is actuating.
Did the Radiator Fan Relay stop when wiggling the wiring harness?

Yes ! Repair as necessary.
.
No ! Go To 3
TEST ACTION APPLICABILITY
3 WARNING: WHEN THE ENGINE IS OPERATING, DO NOT STAND IN A
DIRECT LINE WITH THE FAN. DO NOT PUT YOUR HANDS NEAR THE
PULLEYS, BELTS OR FAN. DO NOT WEAR LOOSE CLOTHING.
NOTE: The conditions that set the DTC are not present at this time. The
following list may help in identifying the intermittent condition.
With the engine running at normal operating temperature, monitor the DRBIIIt
parameters related to the DTC while wiggling the wiring harness. Look for parameter
values to change and/or a DTC to set.
Review the DRBIIIt Freeze Frame information. If possible, try to duplicate the
conditions under which the DTC was set.
Refer to any Technical Service Bulletins (TSB) that may apply.
Visu y inspect the related wiring harness. Look for any chafed, pierced, pinched, or
parti y broken wires.
Visu y inspect the related wiring harness connectors. Look for broken, bent, pushed
out, or corroded terminals.
Were any of the above conditions present?

Yes ! Repair as necessary
.
No ! Test Complete.
4 Turn the ignition off.
Disconnect the Radiator Fan Relay harness connector.
Using a 12-volt test light connected to 12-volts, probe the Ground circuit in the
Radiator Fan Relay harness connector.
Does the test light illuminate?

Yes ! Go To 5
No ! Repair the Ground circuit for an open.
.
5 NOTE: Inspect the Radiator Fan fuse located in the IPM.
Turn the ignition off.
Disconnect the Radiator Fan Relay harness connector.
Measure the voltage of the Fused B+ Output circuit in the Radiator Fan harness
connector.
Is the voltage above 11.0 volts?

Yes ! Go To 6
No ! Repair the Fused B+ circuit. Check and replace any open fuses.
.
6 NOTE: Ensure the Radiator Fan Relay harness connector is connected.
Turn the ignition off.
Disconnect the PCM harness connector.
Turn the ignition on.
Using a jumper wire, momentarily jumper the Radiator Fan Relay Control circuit to
ground.
Did the Radiator Fans operate?

Yes ! Replace and program the Powertrain Control Module in accordance
with the Service Information.
.
No ! Go To 7
TEST ACTION APPLICABILITY
7 Turn the ignition off.
Disconnect the Radiator Fan Relay harness connector.
Disconnect the PCM harness connector.
Measure the resistance of the Radiator Fan Relay Control circuit between the
Radiator Fan Relay harness connector and the PCM harness connector.
Is the resistance below 5.0 ohms?

Yes ! Go To 8
No ! Go To 11
8 Turn the ignition off.
Disconnect the Radiator Fan Relay harness connector.
Disconnect the PCM harness connector.
Measure the resistance of the Radiator Fan Relay Control circuit in the Radiator Fan
Relay harness connector to ground.
Is the resistance below 5.0 ohms?

Yes ! Go To 9
No ! Replace Radiator Fan Relay.
.
9 Turn the ignition off.
Disconnect the Radiator Fan Relay harness connector.
Disconnect the IPM C2 harness connector.
Measure the resistance of the Radiator Fan Relay Control circuit in the Radiator Fan
Relay harness connector to ground.
Is the resistance below 5.0 ohms?

Yes ! Repair the Radiator Fan Relay Control circuit for a short to
ground between the Radiator Fan Relay harness connector and
the IPM harness connector.
.
No ! Go To 10
10 Turn the ignition off.
Disconnect the PCM harness connector.
Disconnect the IPM C3 harness connector.
Measure the resistance of the Radiator Fan Relay Control circuit in the PCM harness
connector to ground.
Is the resistance below 5.0 ohms?

Yes ! Repair the Radiator Fan Relay Control circuit for a short to
ground between PCM harness connector and the IPM harness
connector.
.
No ! Replace the IPM Fuse & Relay Center.
.
TEST ACTION APPLICABILITY
11 Turn the ignition off.
Disconnect the Radiator Fan Relay harness connector.
Disconnect the IPM C2 harness connector.
Measure the resistance of the Radiator Fan Relay Control circuit between the IPM
harness connector and the Radiator Fan Relay harness connector.
Is the resistance below 5.0 ohms.

Yes ! Go To 12
No ! Repair the Radiator Fan Relay Control circuit for an open
between the Radiator Fan Relay harness connector and the IPM
harness connector.
.
12 Turn the ignition off.
Disconnect the PCM harness connector.
Disconnect the IPM C3 harness connector.
Measure the resistance of the Radiator Fan Relay Control circuit between the IPM
harness connector and the PCM harness connector.
Is the resistance below 5.0 ohms.

Yes ! Replace the IPM Fuse & Relay Center.
.
No ! Repair the Radiator Fan Relay Control circuit for an open
between PCM harness connector and the IPM harness connector.
.

 

Thank you so much, *******.

I had the same problem and was geting the "just make another appointment and we will have a look at it" run-around from the dealer.

This solved my problem and the step-by-step was most helpful

Muchas gracias, thank you, Danke'...

JessG

 

you are welcome, I am glad that it helped someone !