i have a svc. eng. light on and i belive the code is 1642 it says coolant relay 2 or 3 is bad but i replaced them and still can't clear the code and i can't get it inspected with the light on i just replaced the rad. and the therm. bled the system and everything is holding temp fine fan kicks on when i turn on the a/c what could be the problem any suggestions would be welcome. i am really starting to lose patience.

 

I pull up the code as being Vehicle Speed Circuit malfunction. Which is usually the speed sensor on the trans that is failing or its associated wiring. That is P1642. The letter in the front of the code is important, it determines the system the code references "P" is powertrain, "B" is Body, "U" is system bus... ya get the idea. Some systems have the same code numbers but he prefix letter will let us know the system. Hope this helps you out.

BTW does your speedometer jump around or not work? Also how close is your speedo to the actual speed?

Massey

 

no letter in front but when i looked up the code it said for f body the fan relay was the problem

 

http://www.njfboa.org/forums/showthread.php?p=529423

this guy was having the same problem turned out to be the opti

 

ok i am kinda new at this electronic crap what is opti and where is it located please be gentle i am new here if its a dumb question i am sorry just trying to figure this out befor i pull all my hair out

 

the opti is the distributor and it is behind the water pump. It is offically called the OptiSpark and the one from GM is troublesome at best. MSD makes a really nice replacement but it will cost you a few well earned $$$'s.

What scan tool did you use? If the MIL is still on then take it to an O'reilly or Advance Auto near you and they have advanced scan tools that will give a reading of the code as well as the description. Some of the simpler scan tools do not always have the ability to read the manufacturer specific data (p1xxx is manufacturer specific). Hope this helps

Massey

 

thanks very helpful as far as the code it was done at an autozone and the computer printed out the diagnosis according to my vin # i have an f body and the code said open or short circut or fan relay 2 or 3 i went as far as taking the relay box off and inspecting that birdnest of wires for connection or frayed wires. nothing looked bad even went under and traced wires back to relay box from fans car runs great holds temp and fans work when i turn on a/c replaced relay with 1 new one and the relay from fog lights on the other (2+3) as soon as i clear the light it comes right back on ahhhhhhhhhhh

 

i also want to say thank you all for you suggestions in a world where time is precious you take the time to answer my questions and you know how to make a newbie like me feel welcome thanks again

 

Trust me here the issue is not the relays. Your computer does not care if they are there or not. Check the speed sensor, it should be the one for the tranny and it is calling out the output side of the sensor. Simply means that the computer is not reading the sensor's output. This code has 2 definitions.

Massey

 

O.k. i will give that a shot and hope its the problem its only $55 so i will find it on my tranny and swap it out will let u know how it goes