I have a new to me 99 2500. I took it on an eight hour round trip drive and on the way back check engine light came on. I didn't notice any drivability issues at all and light went out after 40 miles. When I got home I pulled the codes and found po122 apps voltage low and po237 map sensor voltage low. Do you guys think it could just be a one time glitch or should I investigate asap? Thanks.

Delete codes and see if they come back. Unhook both negatives. When you have them both unhooked, hold one to the positive terminal for roughly 10 seconds. This will completly drain all memory. Then hook everything back up. And, calibrate apps by turn key on and slowly press go pedal to the floor and slowly relase. Do the pedal twice and it will be calibrated

Thank you very much.

That is incorrect. The ONLY thing that disconnecting the batteries is delete the APPS high & low limit. You need to use a scanner to delete codes. It's not like your 88 Camaro....

Look in the "Articles" for our generation for the test procedures for codes. Also look up "Alternator AC noise" for how to test the alternator for AC voltage leakage.

Clean ALL connections, slather with silicone Di-electric grease. ALL CONNECTIONS !!!!!

You could be lucky enugh to just have a corroded or loose ground, or you could need a new VP44 injection pump. It also could be anything in the middle.

 

Also, after having everything unhooked, you need to reset your APPS (Throttle Position Sensor). There should be an article on that, too

 

Ed

Edited April 14, 201411 yr by Yankneck696

Hope you didnt take pulling cables will delete codes. I was directing that towardd reseting the apps and clearns all the tables/memory in the ecm. Only way to clear codes is with a scan tool with the key on, engine off.

Sorry, didn't read it all the way through..... I can be soooo blonde, sometimes....

Ed

Thanks guys. I knew what you meant. I can clear the codes with our shop scanner. I will be checking the alternator output, cleaning grounds, load testing batteries, etc. this evening. Read quite a bit about the electrical noise issues and I am going to try the foil and ground to see if that helps.Thanks for help. Anything else is greatly appreciated.

Foil is just a bandaid. Check the alternator properly & if the AC output is too high, have it properly rebuilt at an alternator shop. Many of the people that used the band-aids (Filters, foil, etc...) have had further issues like frying the ECM/PCM/FPCU (Computer on the VP44).

 

Now, when I said ro check, clean & grease ALL connections, that meant EVERYTHING under the hood. A small amount of corrosion in 1 connector can cause many electrical gremlins.

Ed

Got it. Is it usually the alternator or is it just a toss up?

I would say toss up between alternator, bad sensors, and bad connections. You should fill out your sig so we know what you have!

With the age of our trucks, poor electrical system when new & the funky stuff they put on the roads in Colorado, it would behoove you to go through all connections thoroughly.

 

Ed

Immediate problem solved. Found a bad ground which was my own stupidity. I cleaned and checked all other grounds. Also I went ahead and had the alternator rebuilt by a shop familiar with the problems on these trucks. Like everything else I've replaced it was the original alternator. Now its time to check all the electrical connections. Thanks for all the help. This is an awesome forum.

With the age of our trucks, poor electrical system when new & the funky stuff they put on the roads in Colorado, it would behoove you to go through all connections thoroughly.

 

Ed

When I had my VP out I pulled every plug I could find on my truck and filled it with dielectric grease. They wouldn't have to put all the crap on the road if people would just slow down and drive with some sense!