To get my HMMWV (M1097A2) in good running order... need help.

[DEA AK]

You caught me at the right time. Normally I don't even crawl out of bed for at least another 15 minutes.

Well I am glad I did, I have been up since 2:45 yesterday and today...

I was planning on driving her to work but now I will need to figure out this wiring thing. I thought it was all good, no random wires hanging anyplace in the engine bay.

I do need to figure out the absolute basic wires for the proper operation of the HMMWV though, I do have some random comms wiring or whatnot in the truck but am uncertain about yanking it.

 

[Mogman]

Your truck has a 4 speed so there should be a wire from the 14V stud on the regulator to the 12V connection between the batteries, without it the batteries will be unbalanced and die an early death.
I doubt very seriously the gen not having a ground wire will start a fire, the gen will ground through its mounting bolts but AMG did install one

 

[DEA AK]

Question.

When I first got the truck, it was stuck in limp mode, no trans light. Fixed the limp mode by connecting the 12v wire in the battery box that was cut off. Now it appears to drive well, and seems like its shifting with no problems. It drives on the hwy and of course is loud but I guess that's the military thing.

However, I still don't have a trans light. I pulled it out, tested it and it lights up so at least I know the trans light works.

How can I test to see what is WRONG with WHATEVER if it won't give me blinking codes (when jumping the tcm box)?

The tcm must be getting 12v because its no longer in limp mode. also, the tcm seems to be working since it seems to be shifting gears.

I am sure you all know, I am just trying to figure this out.

Thank you

 

[DEA AK]

Your truck has a 4 speed so there should be a wire from the 14V stud on the regulator to the 12V connection between the batteries, without it the batteries will be unbalanced and die an early death.
I doubt very seriously the gen not having a ground wire will start a fire, the gen will ground through its mounting bolts but AMG did install one

Copy, I just got finished installing a wire - just in case. Thank you

 

[CapePrep]

Question...

Not to jinx myself but my truck runs, seems to shift into all gears fine and the generator gauge works, dips down when I crank and shortly after starting it gets into the green zone, normally right on the mark in that green zone.

BUT... I saw a video that the guy stated that a wiring short / fire could happen if a ground wire wasn't connected to my alternator.

In the picture, I have two wires where B is indicated, however, I do not have a wire where A is indicated.

Is this wrong? I don't see any wires any place in the engine bay that were cut or broken.

The TM that I see is less than helpful as it doesn't show anything connected to the yellow stud.

The final pic is of my truck (with no arrows)

Thank you

I saw that video with the guy saying to ground that connection! He is an idiot! I commented that the video should be removed since it will be a dead short and definitely melt some wires if not worse!

 

[DEA AK]

I saw that video with the guy saying to ground that connection! He is an idiot! I commented that the video should be removed since it will be a dead short and definitely melt some wires if not worse!

I was hoping running the wire would magically fix my trans light issue but, no luck.

 

[Mogman]

I was hoping running the wire would magically fix my trans light issue but, no luck.

That would not have anything to do with the trans light, if the lamp is good then ether the wires have an issue (there should be +12V on one side in the run position) or the TCM is bad.
Actually if you do not have a TCM as in retrofitting earlier vehicles with the 100/200A alternator grounding the 14V terminal is often done, it does not hurt the alt or reg.
The regulator will not "activate" the 14V terminal unless it sees a positive voltage there.

 

[DEA AK]

That would not have anything to do with the trans light, if the lamp is good then ether the wires have an issue (there should be +12V on one side in the run position) or the TCM is bad.
Actually if you do not have a TCM as in retrofitting earlier vehicles with the 100/200A alternator grounding the 14V terminal is often done, it does not hurt the alt or reg.
The regulator will not "activate" the 14V terminal unless it sees a positive voltage there.

I unplugged the light and used the meter to test the plug connected to the truck - it reads 5.96v

In addition to the trans light not coming on, I have also never seen the transfer case light come on the few times I have had it locked in HL or L.

If it its a bad tcm, does the tcm number have to match exactly? Mine is a 2100BB and I see a 2100AA.

It is from 4/15 so do these things fail like the smart boxes?

thanks!

 

[DEA AK]

Can anyone confirm that I am reading this 4l80 troubleshooting manual right...

I think it says...

FOUR wires to the shunt (599A, 599B, 57T, 57C)

ONE wire to rear battery (290/291/537)

 

[Mogman]

I do not see a 57C but other than that you are correct, you need to figure out why you do not have 12V on 657B when the ign. is on (DO NOT forget to unplug the glow plug temp sending unit while troubleshooting the trans)
657B is the female (protected) terminal in the plug that connects to the trans light plug.
If you trans is shifting the other wires you talk about should be good.

 

[DEA AK]

I do not see a 57C but other than that you are correct, you need to figure out why you do not have 12V on 657B when the ign. is on (DO NOT forget to unplug the glow plug temp sending unit while troubleshooting the trans)
657B is the female (protected) terminal in the plug that connects to the trans light plug.
If you trans is shifting the other wires you talk about should be good.

I was just tracing wires off the shunt and it appears as if 57T runs up to the trans relay.

I don't even think I have all those wires on my truck... one small wire to the shunt for sure and then one small wire to the positive terminal.

Thank you for the reply.

 

[Mogman]

It is easy enough to see if you have ground on 57T and 599A-B you just need a test light or meter, it ether has ground or not. the trans will not shift if 57T or 599A-B does not have ground.

 

[DEA AK]

It is easy enough to see if you have ground on 57T and 599A-B you just need a test light or meter, it ether has ground or not. the trans will not shift if 57T or 599A-B does not have ground.

Copy that, thank you.

 

[Mogman]

You have already identified you do not have 12V at wire 657B so that is where you need to concentrate your investigation, make sure you have a good ground on your meter when checking voltage on 657B

 

[DEA AK]

You have already identified you do not have 12V at wire 657B so that is where you need to concentrate your investigation, make sure you have a good ground on your meter when checking voltage on 657B

Copy, thank you.

 

[DEA AK]

So... I have made some progress but have a question about what this TM shows (see pic).

Item 1: testing the trans lamp as outlined, the lamp turns on, nice and bright.

Item 2: tested 657A and it showed 12.5v.

Item 3: tested for continuity jumping as shown and it showed fine.

But, the question is, the next steps talk about the TRANSFER case, not the transmission. Is that right?

My transfer case has never worked but as shown above, my transmission light actually works as mentioned above.

Thank you

 

[Mogman]

That is a typo, there is no such thing as a transfer case check light.

 

[Mogman]

So your trans light now works?

 

[DEA AK]

That is a typo, there is no such thing as a transfer case check light.

Copy, I was just looking to see if some how they were tied together, thank you for the reply.

 

[DEA AK]

So your trans light now works?

I unplugged the trans light itself and it lights up.

On the truck side, I connected the positive lead on the female side of 657, and then connected the negative lead and the light did not turn on.

I then touched the negative lead of the light to the block and the light turned on.

Looking at the diagram (below), I connected the negative side to B9 at the back of the B plug and the light did not turn on.

I am assuming that the MIL CONTROL circuit is bad???

Knock on wood... the transmission shifts but the trans light has never worked for me.

I am assuming that both leads out of the trans relay are positive since 291D goes tot he ignition feed and then 290B / 291A go to 12v battery.

with that assumption the power from 290C / 291C would be sent to the light but wouldn't 'turn on' until the B9 / MIL CONTROL circuit told it to.

If none of that makes any sense, please let me know. I could be completely wrong. I am not a tech but it could be possible the TCM is still running the transmission without the trans light actually blinking codes??? maybe??? who knows???

Thanks,
David