@002 Dodge Ram. Check engine light on. Code 1491 at autozone yielded 001 open or shorted radiator fan relay 002 open or shorted circuit condition, 003 ECM defective, Does this vehicle have an electric radiator fan? what is ECM? and how can I further determine what the problem is?

Here's a link to the P0340 code,and P1491.Powertrain Diagnostics Manual P-1491 Radiator Fan control relay circuit
Set condition: An open or shorted condition is detected in the radiator fan relay control circuit.

Possibilities:
Fan relay ground circuit open
Fused B+ circuit open
Rad fan control relay defective
RF relay output circuit volt cycles over to batt voltage
RF relay control circuit open
RF relay ctrl rly ckt wir harness observable or intermittant defect
RF relay ctrl ckt short to ground
Defective PCM

Get out your Multimeter.

Hello jhonney21,

The P1491 is Radiator fan control relay circuit code. It is set if an open or short circuit is detected in the radiator fan relay control circuit.

Regards,
netvan

Radiator cooling fan relay or circuit.

you have an open or shorted condition detected in the low speed radiator fan relay control circuit. hope this will help!!!!

ok ,generally on this car the fan relay is located in fuse box near the battery car

Don't rush to replace the fan itself until you have tested it. Check the fan relay and relay fuse inside the vehicle. Hopefully it will be just a failed relay and replacement ($12 at dealer) or/and an inexpensive 10amp or 30amp fuse. There can be multiple issues causing this code.

In my case, the fan relay failed (burnt). 2000 Dodge Durango. The PCM was also damaged and requires replacement, awaiting delivery. A remanufactured PCM can be purchased online for substantial less than at the dealer. We tested the fan by supplying power directly to the fan and it runs fine. We had to remove a cover (easy to remove) under the vehicle near the fan to gain access to the connector Use a fused link for testitng to prevent damage during the test. Using a multimeter, I found power 12.5volts from the 30amp fuse circuit which supplies the power for the fan, 12.5 volts from the PCM circuit with the key on, but only 5.16volts from the 10amp fuse circuit with the key on. A continuity test showed the 10amp fuse inside the fuse box inside the vehicle was good. The 30amp fuse in the power distribution box was good when tested for continuity. Checked resistance on all curcuits and they were well within limits. I also checked the wiring to the fan for continuity and resistance. After my tests were completed, a Dodge technican concluded the PCM is bad and is not grounding the circuit as it should. If you want to troubleshoot this yourself, see if your local library has access to ALLDATA which will have diagnostic information and the diagrams of the circuit involved. A Haynes manual for the vehicle, I purchased one at Autozone, can be helpful also.

you will need to replace the relay for the fan because it is stuck on. You can look on autozone.com for free online repair guide. It will have the relay location unless you have a repair manual of your own. But it is the relay.

34 = Speed Control Solenoid Circuits: An Open or Shorted Condition has been detected in the Speed Control Vacuum or Vent Solenoid Circuits.
35 = Radiator Fan Relay Circuit: An Open or Shorted Condition has been detected in the Radiator Fan Relay Circuit.
That 5 at the end should have had another 5 after. Did it? 5-blinks and 5-blinks means the system has finished sending the Codes.

P-1491 RADIATOR FAN CONTROL RELAY CIRCUIT.

1491-radiator fan relay control circut
1492-ambient/battery temp sensor volts to high
check and make sure your radiator fan is coming on
samboiv