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code 46

9

94Jake

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Location
Kansas City
I'm getting a code 46, Mill Fault, I'm guessing this is just a ground issue, has anyone ever traced this harness? Or dealt with this code?

94 chevy 1 ton dually, 133k miles, 4 door, 2 wheel drive, automatic, with a turbo master and towing prom
 
Does your check engine light work? It may be a failing bulb or a loose connection somewhere between the ECM and guage cluster. Code 46 sets if the ECM detects a problem with the MIL(check engine light) circuit. If the light is working, but your still getting this code then it is either a loose or bad connection, a bulb going bad, or a failed ECM.
 
The light works, but it seldom goes out. I took the gauge cluster out and checked that connection, but didnt know where to go from there without completely tearing the dash out on a recon.
 
Hi Jake good to talk with you on the phone sorry I could not be much more assistance here is what the 94 GM manual has to say on the issue, if electrical conns are clean per manual looks like a rare occurrence of faulty PCM which I guess can happen it is rare.

Guys in KS Bill Heath called me other day asking if I knew anybody near Jake, off top of my head GM Guy is in KS profile says NW KS; Jake is NE KS the member locator http://www.thetruckstop.us/forum/showthread.php?4714-6-5-member-locator may also have somebody close in it as well anybody near Jake that can recommend someone to assist hands on, he like Ferm new father and has full plate and could use a helping hand, farming is his other lament other than having a 6.5 that currently is not playing well.

View attachment Code 46 troubleshooting 94 year 6-5 trucks.pdf
 
I would check the ground for this. On a 95, it is the one on the back near the fuel filter but not sure on a 94.
May be the same.
 
As you can see from the schematic circuit 419 which faults the code 46 does not have a lot to it, sort of an on/off situation, folks what are your thoughts, if wiring connections are good, we have a suspect PCM here ? Anybody have a loaner PCM he could try out or know where in KS would be a good junkyard he could try to find another, his GM prom and his Heath Prom both have the code 46 with the PCM installed now.


View attachment Code 46 circuit 419 PCM schematic.pdf
 
Just on the off chance it might be gnd related, have you checked the PCM gns, pass side rear head intake stud couple of gnd wires there those go to the PCM, those have to be spotless clean use your meter on ohm scale to gnd you want to see as close to 0 ohm resistance to gnd as possible.

Have a read through here http://www.thetruckstop.us/forum/showthread.php?14596-6-5-grounds to see more about importance of gnds from our technical reference library http://www.thetruckstop.us/forum/showthread.php?13960-Sticky-6-2-and-6-5-Technical-Library
 
I've got my 95 ECM that had less than 500 miles on it. I think it was a new one, not a reman, but I know it was a genuine GM. I spent $125 for it just before my head gaskets blew out, and another $40 for the updated PROM in it. I was hoping to get $100 out of it if anybody wants it.
 
The 95 wont work on the 94 will it?

And I did read the tech article on grounds, I have cleaned the PCM's on the back of the engine, but have not got to all of them yet.
 
need to find out what IP he has possibly a 5068 if so I have a pcm that will fit but the gear ratio might be off, but I guess the prom should take care of that.
 
94Jake said:
The 95 wont work on the 94 will it?

And I did read the tech article on grounds, I have cleaned the PCM's on the back of the engine, but have not got to all of them yet.
Click to expand...


My failing 95 ECM ended up in a 94 1500, and ran fine(except for the intermittent fishbite issue that I replaced the ECM for). Others have also swapped 94 for 95 ECM's and vice versa without problem.
 
THEFERMANATOR said:
My failing 95 ECM ended up in a 94 1500, and ran fine(except for the intermittent fishbite issue that I replaced the ECM for). Others have also swapped 94 for 95 ECM's and vice versa without problem.
Click to expand...

I got a different ECM from yard today, any special directions to hook up?
 
94Jake said:
I got a different ECM from yard today, any special directions to hook up?
Click to expand...

Plug it in and see if it codes. It may throw a code for tdc offset error, but most likely it won't. Also unless teh new ECM came from a 2500/3500 truck, I would swap PROM chips from your old one to it just to make sure the new ECM doesn't have an S engine chip in it that will look for an EGR valve.
 
The other issue I'm having is after an hour on the road the truck will die then start back up and run. It might run again for awhile, it might not. I have changed to heath's remote pmd and it passes the lift pump test the ip is not that old (one year). This is why I was trying to get codes. How do I tell which ip model I have? What sensors could be affecting this? Ops? Tps?

I really appreciate all the help.
 
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