What does the diagnostic test code P1491 means?

Definition of Diagnostic Trouble Code P1491 Acura: Exhaust Gas Recirculation (EGR) Valve Insufficient Lift EGR Honda: Exhaust Gas Recirculation (EGR) Valve Insufficient Lift EGR

Check sensor that sends the message to the fan.Should be in radiator.

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.

Code P1491 in Honda/Acura vehicles means insufficient EGR valve lift. Note - this is not the same as 0401 for EGR low flow when you have to clean EGR passage in the intake manifold. If code 1491 is not accompanied with 0401 - that could be faulty EGR valve itself. Try to reset the code, and if it will return soon - replace EGR valve. If, however you see both codes together - cleane the manifold passage before you replacing the valve.

If the EVAP canister is OK, and there are no other visual damage to the EVAP system (e.g. loose or broken hoses), replacing the vacuum cut valve bypass valve takes care of the problem.

I have a code p1491, what does this mean?

Diagnostic Test Code (DTC) P1941 is NOT a VALID code for a 2003 Jeep Liberty. Are you sure you are reading (and posting) the code correctly?

Also, when asking about DTCs it is really helpful to also mention which engine your vehicle is equipped with.

Trouble code P1491 means: Radiator fan relay control circuit

Trouble Code: P1491 You PCM does not sense current to radiator fan when it turns it on. Is the fan coming on or not? Usually not when you have this code. Problem can be with the fuse, relay, wiring or fan itself. First check the fuse. If good, next try swapping the relay with another one in the engine compartment relay box, such as the horn relay.
Let the car warm up and see if the fan will come on. If yes, get a new relay. If not, either use a test light to see if there is voltage at the fan connector when the engine is on and hot, or else test the fan motor by hotwiring it to the battery. If none of this works, please get back to me for how to troubleshoot the wiring.


Radiator Fan Control Relay Circuit Malfunction
Possible Causes:


Radiator fan control relay circuit is open or shorted to ground Radiator fan control relay circuit is open (test power to IGN) Radiator fan control relay is damaged or has failed PCM has failed

Trouble code P1491 means: Radiator fan relay control circuit problem.