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

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

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

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.

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.

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.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.

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.

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.

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.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!

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

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?

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.

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

when you say on do you mean accessory mode or the first click before the fan/radio turns on? ThanksYep, that's what he would be referring to. Some call it the key dance!

I don't know if this sequence is valid on your model.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.

shajaan6

The "on" position is the key natural position just before the springloaded position that activates the starter relay.

shajaan6,
I thought I posted, but I must have put the response elsewhere. The "on" position is the natural key position immediately before the starter spring loaded position.

If you have an active imagination, the excruciatingly boring activity of counting the flashes leads to miscounts and redos. The whole process should not take more then a couple of minutes.

great thanks, im going to work on my car now.

Well the radiator fan relay was bad, 60 bucks for the stupid thing. It wont be in untill saturday, ill post saturday evening after i put it in, let you all know if it worked. Thanks alot!

Well the radiator fan relay was bad, 60 bucks for the stupid thing. It wont be in untill saturday, ill post saturday evening after i put it in, let you all know if it worked. Thanks alot!Hope everything works out for you. Keep me posted.

Thread Summary....

Aggrivation caused by actron 9035 erroneously reporting 1491 error code as MAP Sensor Fault when Fault was Fan relay Fault.

Question: did engine every overheat?

No but on further inspection the guy i got the car from hard wired the fan to the power center. Thus explaining why the car would overheat when AC was on and no other time, THe coil must have still been good in the relay sending singnal to the computer alls well. When really it wasnt, coil finally went bad and put it in trouble mode. Again, ill post tomorow evening about this bastard. BTW I am in need of a new shift cable, linkage from shifter from knob to transmission, If you guys know where i could get one cheap id appreciate it, I am unemployeed and need to get car working so i can start working again. Thanks
James

BTW I am in need of a new shift cable, linkage from shifter from knob to transmission, If you guys know where i could get one cheap id appreciate itAre you sure you need a new one? You may just need to replace your bushings. THESE (http://www.boogerracing.com/) are good replacements. Modern Perfomance sells them also w/free shipping! If you do need the cable, try your local junkyard or a parts place like Autozone, NAPA, etc.

Thread Summary....
Aggrivation caused by actron 9035 erroneously reporting 1491 error code as MAP Sensor Fault when Fault was Fan relay Fault.
Actually he used the Haynes manual to interpret the code. The Actron reported the correct code 1491, which was the Fan Relay.

I am corrected. This entire affaier is the result of the PCM correctly reporting the error code and incorrect meaning being printed in the Haynes Manual. Is this correct?

Also..There is a TSB on the 96 Neon whereby a slave solid state relay was installed to alleviate headlight dimming dimming when the fans came on. I recalled seeing the errant red wire installed after I bought the neon. It tapped into the PDC and the relay was mounted behind the front bumper. I was done in the Dodge service shop in Ypsylanni. I always considered it a messy fix. I wonder if this fix is the root of the fault. My initial fan relay is there, but so is the SSR. I never traced the original wires.

No but on further inspection the guy i got the car from hard wired the fan to the power center. Thus explaining why the car would overheat when AC was on and no other time, THe coil must have still been good in the relay sending singnal to the computer alls well. When really it wasnt, coil finally went bad and put it in trouble mode. Again, ill post tomorow evening about this bastard. BTW I am in need of a new shift cable, linkage from shifter from knob to transmission, If you guys know where i could get one cheap id appreciate it, I am unemployeed and need to get car working so i can start working again. Thanks
JamesAny updates, how's she running?

Update... A little upset here.

There is no update on the car. But dont shop at autozone....

Ordered for 3 days, on saturday called in at 1:30, 3:00, 5:00, 6:00, finally at 6:00 they told me the order was canceled because their warehouse didnt have the product. I was infuriated because if they did their damn job and checked the order like they said at 1, 3, and 5, i could have got my money back and drove over to the dealership that closes at 4pm on saturdays, but since they waited till 6 the dealership is now closed and i cant get my part on saturday, nor sunday becuse parts is closed on sundays. SO now its monday and im waiting for my mom to get home from work so i can get her car to get it from the dealer, I will have an update today. Sorry :(

Stupid autozone....

Yay, thanks to everyones help I was able to find the problem.

I picked up a new relay today, set me back 90 bucks. Oh well, put that bad boy in and everything worked out great, no more check engine, and car is running great, Thanks again everyone. Oh yes, and i am the proud new owner of an Actron 9135. Hehe... Thanks, was great help from everyone.


THANKS!!

James

Yay, thanks to everyones help I was able to find the problem.
I picked up a new relay today, set me back 90 bucks. Oh well, put that bad boy in and everything worked out great, no more check engine, and car is running great, Thanks again everyone. Oh yes, and i am the proud new owner of an Actron 9135. Hehe... Thanks, was great help from everyone.
THANKS!!
JamesGlad to hear everything worked out for you. I see you got a new toy also, I got mine off eBay a few months ago! Glad I could help out also.