Problems with my 1045a2

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2mas-

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Hi,

I have a couple problems with my M1045a2

First problem is that my transmission is in "limp mode" only does 1-2 gear. I have put the transmission in diagnostic mode with a "jumper" and the code is 7-3 that says problem with the Pressure Control Solenoid. I have cheked the wiring and cant find any shorts on the wiring for the transmission. So I am ready to change the PCS to see if that will fix the problem. The PCS is inside the transmission, I have to drop the pan to get to it. Can I just drain the transmission for oil and pull the pan and change it? Can I just fill back the oil I have drained from the transmission after? What is the procedure after the drain and fill up do I have to cycle it throug every gear to make the oil float around in the transmission?

After this is done i read that I have to reset the errorcodes with pushing the red button behind the passenger seat. Shall it pressed when the HMMWV is running, ignition on, ignition off or with the battery disconnected?

The second problem is when I disconnect the negative on the rear battery the lights still can operate on 12v. The +14 output on the regulator makes a negative. Is it supposed to be like that?
 

Retiredwarhorses

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Your ATF in the trans is how old now? Unless all fluids were changed after the auction, I would be replacing all fluids and filters.
No idea what your saying on the lights and such
 

Retiredwarhorses

Well-known member
Steel Soldiers Supporter
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Location
Brentwood, Calif
Hi,

I have a couple problems with my M1045a2

First problem is that my transmission is in "limp mode" only does 1-2 gear. I have put the transmission in diagnostic mode with a "jumper" and the code is 7-3 that says problem with the Pressure Control Solenoid. I have cheked the wiring and cant find any shorts on the wiring for the transmission. So I am ready to change the PCS to see if that will fix the problem. The PCS is inside the transmission, I have to drop the pan to get to it. Can I just drain the transmission for oil and pull the pan and change it? Can I just fill back the oil I have drained from the transmission after? What is the procedure after the drain and fill up do I have to cycle it throug every gear to make the oil float around in the transmission?

After this is done i read that I have to reset the errorcodes with pushing the red button behind the passenger seat. Shall it pressed when the HMMWV is running, ignition on, ignition off or with the battery disconnected?

The second problem is when I disconnect the negative on the rear battery the lights still can operate on 12v. The +14 output on the regulator makes a negative. Is it supposed to be like that?

And I suggest downloading the technical manuals
 

2mas-

New member
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Location
Norway, Kr.Sand
Your ATF in the trans is how old now? Unless all fluids were changed after the auction, I would be replacing all fluids and filters.
No idea what your saying on the lights and such
When I unhook the batterycable going to the negative (-) on the rear battery it wouldnt cut all the power to the Hmmwv. Lights still work and they glow like there is 12v getting to them. I see that it is the cable going from the Dual regulator +14 connector that makes ground between the batteries that are hooked up together. Is this normal? I have read some place that when the truck has the 200amp alternator with dual regulator the +14 should be grounded when not in use, but will it go to ground when the truck is not running? Sorry for the lanuage
 

Retiredwarhorses

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The 14v from the regulator is required for 4L80e trucks to prevent an imbalance in the battery’s because the TCM is wired to the rear battery, the TCM and trans are 12 volts. Remove the 14v tap from the regulator and try it, if it fixes the issue, your issue is the regulator is bad.
Your trans is in limp mode most likely can be no power to TCM, make sure you are getting the trans lamp on next to shifter when the key is in “run” and goes off when started, if no trans lamp on in run position check to make sure the TCM lead is on the positive terminal of the rear battery.
post a pic of the battery wiring,.,,
 
Last edited:

2mas-

New member
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Norway, Kr.Sand
Thank you for answer,

Yes I understand that the 14+ tap is to charge only the rear battery to balance it for the transmission and TCM. I tried to change the regulator for a new one i bought Niehoff N3135. When I started it with that regulator it started to come some smoke from the alternator and smelled burnt. The regulator that came with the HMMWV was a Niehoff N3117, I changed back to that one after the N3135 failed me. Both of the regulators make ground when the rear negative battery cable is hooked off, I can turn on lights and they will glow with 12v
3117.jpgIMG_0499.jpgIMG_0502.jpg

The voltage is different when I measure on the +14tap with the diffrent regulators (Truck not running)
 

AAVP7

Member
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Location
Dortmund, Germany
On vehicles with the dual-voltage alternator, you should NEVER switch on anything when you´ve unhooked just one battery ground. You´ve discovered the reason: With the ground connection of the rear battery removed, the alternator and every 12 volt accesory (at least your transmission, and any possible 12 volt accessories you might have added) will act as ground for the front battery.

The problem with this is that the current is flowing BACKWARDS through every 12 volt device, so that might well kill something.

The transmission are even "online" all the time, but they have a rather high resistance, so there´s not much current flowing there.

So for dual voltage systems, better remove both battery grounds before tinkering on the electrics.
 

2mas-

New member
39
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0
Location
Norway, Kr.Sand
On vehicles with the dual-voltage alternator, you should NEVER switch on anything when you´ve unhooked just one battery ground. You´ve discovered the reason: With the ground connection of the rear battery removed, the alternator and every 12 volt accesory (at least your transmission, and any possible 12 volt accessories you might have added) will act as ground for the front battery.

The problem with this is that the current is flowing BACKWARDS through every 12 volt device, so that might well kill something.

The transmission are even "online" all the time, but they have a rather high resistance, so there´s not much current flowing there.

So for dual voltage systems, better remove both battery grounds before tinkering on the electrics.
Ok didnt know that, thank you for the tip. I thought there were only going to be one ground when the batteries are series connected. So do you think my situation with alternator cable giving ground when the vehicle is not running is normal?
 

Retiredwarhorses

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Guys, killing the ground on the rear battery should and will render EVERYTHING dead....no switches will work, this is the safest way to perform ANY electrical work on the truck.
 

2mas-

New member
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Location
Norway, Kr.Sand
Location updated, sorry havent been on the forum for a while.
Did some mechanic work on the Hmmwv yesterday. Dropped the pan for the transmission and found the electric wire for the PCS was hanging unconnected. Hooked it back on and made sure that it was on right and tight now. Also measured the ohms on the PCS and it stays in the range of 3,5-4,5 (4,3). I also found the magnet strip hanging on the filter almost blocking the filter hole. I suppose it aint going to be like that?
Im going to change oil and filter, is there anything else I should check when the oilpan is bolted off?

Magnet on filter.JPGLoose PCS cable.jpgShiny pan.jpg
 
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