2 MAP sensor codes and engine idles high after new IAC

[1997c1500]

I bought a new duralast idle air control valve for my 1990 c1500 with the 5.7. It now idles high. Put the old one back in. It’s a little better but now I have a code for Map sensor voltage is high and the map sensor voltage is low. I am stumped on why my truck runs like garbage.

 

[GoToGuy]

Did you measure pintle extension and follow reset procedure in service manual? What codes? High , low, or both ?

 

[1997c1500]

Did you measure pintle extension and follow reset procedure in service manual? What codes? High , low, or both ?

Both. I have also found like 4 different reset procedures. I do not know which one to follow. I also don’t have the ALDR thing I’ve heard about.

 

[GoToGuy]

The ALDL is GM nomenclature for Assembly Line Diagnostic Link. Also known as, depending on year and shape, ObD 1, or Obd 2 connector port. Generally identified by whether your an obd1 or obd 2 vehicle.

 

[1998_K1500_Sub]

I have a code for Map sensor voltage is high and the map sensor voltage is low.

What is/are the code(s)?

@1997c1500, do you have a copy of the factory service manual for your year? There available for download on GMT400, if not. They can be found here:

88-98 Service Manuals

Over the years I have collected a bunch of GM service literature. Links to PDF Scans of service and STG manuals and a links to the Parts manuals. You'll need the FREE Adobe Acrobat reader to open these files. Get it directly from Adobe here {http://get.adobe.com/reader/} If you're not...

www.gmt400.com

For that matter, the factory service manual should have troubleshooting flowcharts for those MAP error codes; those will likely provide some insight.

@GoToGuy mentions a good point, the IAC may not be performing as expected for the reasons he stated. IIRC, the IAC will eventually find its "desired" operating condition after some period of time / some number of engine on/off cycles, w/o a "reset procedure".