My daughters 1999 Neon (automatic with 2.0 SOHC) is displaying a P1491 code. Originally it was showing both a EGR problem and the 1491; I replaced the EGR valve and cleaned the EGR tube which seems to have taken care of the EGR issue, but the 1491 keeps coming back even after I turn off the "check engine light". I know the P1491 has something to do with her fan circuit. I found that her fans operate all the time and don't turn off with the key on, even when the engine is cold. I'm figuring that either the relay or the computer is at fault. Would this cause the 1491 code? I'm figuring if the relay was open or shorted it would show a code, but continuously on? Any ideas?????

Thanks a bunch!

Dave Young

 

Relay would be my first guess.

 

But would it cause a 1491 fault code, ya think?

 

I've got more info since I first wrote. Jumping deeper into the car I found the reason the fans are always running is that someone in the past has hotwired the fans to a switched power source inside the fusebox under the hood (the fans run only when the ignition is on). I replaced the fan relay with a used one bought from EBay, but the "check engine" light still came on. I took another look at the relay and wiring and found one wire was actually broken in two at the fan relay connector and was severely corroded (it looks like the battery had been leaking at one time). The fun part was taking the connector apart to fix it. But I got it apart, and was able to get enough wire loose from the wire loom to solder it back together and I sealed it with some heatshrink. Good thing is that I now don't have the "check engine" light on anymore. Before, it was always on, and would come back immediately after clearing it. I need to go deeper into the wiring to see if whoever hotwired the fans may have disconnected the fans from the cars wiring (I'm hoping that I can get the pcm to turn the fans on/off), but at least I'm getting somewhere.

I also understand the coolant sensor sends the signal to the pcm to turn the fans on/off and that both the gauges and pcm read from this sensor. Does anyone know which of the connectors go to the pcm, or how to test the sensor? The gauges in the car are operating normally.

The car, in the past, had been in an accident and damaged the front end. I'm not sure if this condition came from the wreck or not, but I've found other damage that was jury-rigged, probably so they could sell the car.

Thanks!

Dave Young