Jump to content

Unable to connect to PCM module

jnich74

Recommended Posts

jnich74 New Member

jnich74

Posted
Posted

Hi everyone,

 

Truck: 2000 Chevy Silverado 2500

 

I am having trouble locating a pin out for the PCM module that the computer hooks up to.

The mechanic I went to, to do the inspection tried to hook up the computer and couldn't get power. He did this with me.

He mentioned the float gnd having a short as a possibility.

 

Questions:

1.) Why would there be no power to the module?

2.) Anyone have a pinout?

3.) What are the possible causes?

4.) Can the PCM be bad and how can I diagnose that?

 

Recent repairs:

- Replaced Alternator (Alt was draining battery)

- AC work (jumpered low pressure switch to test compressor operation (worked))

- AC re-pressurized R134

- Found directional lighting issue (forgot how i fixed think it was just the connection)

 

Needed to be done:

- Full exhaust system all the way to eng block manafold

- Engine manafold bolts are broken off in block (possible need to pull engine to get at)

If anyone has ideas on how to do the above I am all ears

- Transmission diags (slipping)

 

Thanks all

 

 

davester Senior Enthusiast

davester

Posted
Posted

You can get at the front three exhaust bolts through the wheel well, and the rear one, if it's broken off in the head so nothing is sticking out, I would suggest instead to buy an aftermarket kit that bolts into other, unused bolt holes in the head, and then has a bolt that clamps down the exhaust manifold. It's a different kit for each side.

 

The ones I bought are by Dorman, seem pretty sturdy, and did the job. Getting the exhaust manifold fully bolted down made a huge difference for me [as air was getting into the exhaust stream throwning off the O2 sensors badly]. Course, now I'm pretty sure I need new cats :-(

 

Just realized, I don't know what motor you have. I've got the 6.0L gas engine, and this stuff worked for me. For other motors, your mileage may vary.

txab Senior Enthusiast

txab

Posted
Posted

When you're speaking of "power", do you mean when he hooks into the OBDII port he gets nothing? If so try checking the fuse, the cig lighter is on the same circuit as the port, iirc

jnich74 New Member

jnich74

Posted
  • Author
Posted

Thanks guys

 

TXAB: I was able to find that fuse and I remembered last year i removed it trying to find a short. That was a big help I just replaced it and plan to check this afternoon if I can hook up OBD and see if I can get a read out. If I can I can this thing inspected now.

 

Davester: I'll have to look into that the rear bolts are broken off in the head so Ill have to check out the kit (both sides too) but I don't have any pics to show. It is the V8 6 liter engine. A friend and I will check this out tonight and ill report back. I may just pull it and machine it to make sure everything is good before winter and before plow season starts.

 

I'll let you guys know. Thanks again

  • 2 weeks later...
jnich74 New Member

jnich74

Posted
  • Author
Posted

Just an update the fuse took care of connecting to the OBD reader.

 

About to pull heads next week and re machine them.

-- Losing too much power now a friend is going to help me navigate this and I am paying him too.

1300total

600$ parts

400 machine shop

300 labor

 

So much going on with this truck..Need to replace exhaust piping and muffler and then tires and I hope thats it for awhile.

Thanks for your help

davester Senior Enthusiast

davester

Posted
Posted

well, if you have the heads off, that generally makes it a lot easier to get the broken bolts out of the head, like welding a nut to it if it's close to flush, or using an easy-out or drilling it out and putting in a heli-coil type thread.

 

I would do that [and then only use new bolts for the exhaust manifolds] rather than using the third-party clamping solution, as it's easier to work on later.

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Latest Articles

  • Posts

    • needafix
      Brake Bleed Procedure

      By needafix · Posted

      I'm not sure if this should be a reply on this thread or a new topic, let me know if it's out of place. This my first post. Thanks 85077522 - ACDelco GM Genuine Parts Brake Master Cylinders. Anyone else had to replace this brake master cylinder yet. I didn't do any brake work, it looks like new parts and I've had the truck for about 4k miles. When it started to throw codes I did the calibrations with a bidirectional scanner and got the codes to clear but they came back so i did the routine; base bleed, automated bleed and final base bleed. All that with Bosch ES16-32N fluid (please look it up). That seemed to fix it but 100ish miles later it failed again so I ran the same process but with a pressure bleeder this time and got the same results, fixed for 100ish miles. The original fluid looked bad and I thought I got most of it out. The codes; P25A2, C05B0-00, C2A1B. I can get them to clear but not for long. The C05B0 indicates a leak in the front circuit (which is bone dry) so I'm thinking of doing the bleed process on that front again today and I don't know if that's taboo to just do the front but at this point it seems like it's worth the try anyway. The new master cylinder/module unit is supposed to get here today. But now I'm pretty much convinced this install is over my head. I've called several shops and some mobile guys that I know but this thing is like radio active material scary wise. I did get 2 local shops say they should be able to do it, one says he has the SPS2 programing capability. And with the battery disconnected is there supposed to be pedal resistance, mine is to the floor, then if I pump it I can get some resistance.
    • KARNUT
      Slate Electric Truck

      By KARNUT · Posted

      I wasn’t commenting on your post. Certainly wasn’t arguing. I was making an observation on my long term experience with supposedly proper length of driving for proper heat cycles. Works for me. Although I have seen water or vapor come out of exhaust when vehicles weren’t run very long and shut off. It’s very humid in the morning. Then hot and humid. 
    • Grumpy Bear
      Slate Electric Truck

      By Grumpy Bear · Posted

      Not what I said but I can work with it anyway. Complete combustion produces CO2 and H20. When it's cold enough you can 'see' it as water vapor but it is always there and more so the better the tune up. It's physics, not an argument. In a cold motor when the cylinder jacket is below the condensation temperature the water goes to the pan and not the PCV system. Heating the oil moves it from liquid to vapor where it is removed by the PCV system. When and how much depends on temperatures. Of the air, the water and so on. It has little to with the humidity. Water is a combustion product.  
    • Chuck FB
      2 speed transfer case optional now?

      By Chuck FB · Posted

      I can only guess as well that something was clicked on that brought you to the half ton choices by accident. By all means try again and chose the 3500 and sort out that its the cab and box configuration you want and choose four wheel drive ( rather obvious to have a transfer case ) and to make sure the dually isn't chosen. I find or at least did a couple of years ago when I was sifting through the options that it would sometimes jump ahead after choosing the series of truck and in this case 3500 and skip some of the other initial configuration choices and have to watch the heading bar and sometimes back up by choosing the first in the series of option break downs. I think sometimes the computer will remember items that were last chosen and skip over the first part. Anyway go through it all and depending on the trim level chosen and I think the LT is one that may fall into that where the option of having the 4 high auto transfer case can be chosen, where as a High Country doesn't show that option as it just comes with the fancier ( not necessarily better though in terms of potential problems ) transfer case but for sure both transfer case choices are equipped with high and low range in the HD truck segment. Like Newdude said who works at a dealership, its the half tons that are the ones that will come with the single speed unless certain options or trim levels are chosen that add the two speed transfer case but as your looking at an HD, you don't have to worry about that hot mess.    One item that at least didn't show up and not sure if it does yet or not in the HD options on the manufactures pubic website is the upfitter in cab switch option if one is desiring that. Unfortunately its not wired in at the factory but the panel with the switches is on the dash but the wiring harness to be installed gets tossed under the rear seat to be installed by whomever after the fact to complete the installation. 
    • Donstar
      Navigating senior years.

      By Donstar · Posted

      Yesterday we brought home a 6yr  old Havanese dog from a nearby SPCA.  We've had her for 24 hours and we are delighted with how well she is adjusting to her new home.  It  was a huge decision to adopt a dog at this stage in our lives but we believe we made the right choice!   it was reported that her first 6 years were ones of neglect.  I think she's already realizing her life is going to get a whole lot better...  so is ours!    

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...