shajaan6

I have tried everything i can think of on this damn car, i need to fix it by tomorrow because im way late in paying my tags, lovely california i gotta smog it before i can do tags. Here is my delima with my 97' SOHC neon

I am recieving error code 1491, which is map sensor voltage too high or too low...

Metered voltage into map sensor, read 4.99, haynes says should be 4.5-5.5

output in accessory reads 4.14, haynes says should be 4.5-5.5

Output in idle read 1.25 haynes says should be 1.5-2.5


I have replaced map sensor 2 times, thought maybe new sensor was bad out of the box, checked all vacume hoses, 45PSI in fuel pressure, I have absolutly no other ideas for this car.... any information that would help me get the answer would be greatly appreciated, thanks in advance from the new member.

-James

das2123

Did you reset the PCM after you installed the new sensor?

shajaan6

Ofcourse I did, but one wierd thing is when i have worked on my car before, i reset the code and start the car and the SES light is off and turns on after a few seconds, when it did not work, but when i reset this error, the second i turn the car over the light is back. If it matters I have an OBDII device. THanks again in advance,

James

das2123

How did you reset the PCM? Pulling the fuel pump fuse or disconnecting the negative terminal on the battery? Sometimes pulling the fuel pump fuse doesn't always work for me. Are you sure it was your MAP sensor, it could be the IAT sensor as well. At any rate, make sure the sensor in seated correctly, and free of any debris. Thats all I can think of right now.

shajaan6

I cleared the PCM pressing the "ERASE" button on my OBD2 Tester. But like i said, test reading is 1491, according to the book 14** is map sensor voltage too high or too low.

das2123

OK then, you may have to look at any wiring that goes to it. Make sure no wiring is exposed. Other than that, I am stumped just like you.

das2123

Hey shajaan6, when I check code P1491 on my DTC Lookup software it says Radiator Fan Relay Circuit. P0107 & P0108 are the voltage codes. What kind do you have? I have the Actron P9135.

shajaan6

I have the actron 9035 i believe, the book that came with it has no listing for p1491, my hayens book says 14** is map sensor voltage too high or too low.... I think your looking at the 00+ codes, if you are yes 1491 is fan relay. I am first gen neon 95-99, I really appreciate all the help you have given me though.

das2123

Nope, I have a fisrt gen neon. I even put your car into my software and it says fan relay. The Haynes book is wrong in some areas, that may be one!

shajaan6

Well... If thats the case it changes everything, I will check that tomorrow first thing.... Hopefully thats my problem.

palindromelol

shajaan6,
Is the MAP Sensor voltage the only signal out of wack? I have discovered 0.25 V elevated grounds due to cracked insulation on a A/C circuit. The elevated ground was disturbing an array of signal (O2, RPM, etc) My O2 circuit corrected when I pulled the A/C relay. Were you doing maintenence elsewhere?

palindromelol

Shajaan6,
Did you try the key on/off/on/off/on count the flashes trick. That takes the decoding out of the loop. I have a 96. I turn the key on (not to start), off, on, off, on then wait. The computer flashes your engine service light to create digits of the error codes. 55 is the sequence to identify end of code transmission. I don't know if this sequence is valid on your model.

shajaan6

when you say on do you mean accessory mode or the first click before the fan/radio turns on? Thanks

das2123

Yep, that's what he would be referring to. Some call it the key dance!

das2123

It is valid on all first gen neons, don't know about second gens. It also works on alot of dodge vehicles. Don't know which ones for sure though.