HMMWV in Limp Mode DTC 53 4L80E Transmission

[Mariner]

Has anyone dealt with a DTC 53 code? The transmission warning light comes on when vehicle is on run to warm up glow plugs. Goes away when it is running (Still stuck in 2nd gear) and comes back on when the ignition is switched to engine off. I was not sure if there was something that is a typical offender for causing this code I should look at.

Thank you in advance and any help is welcomed. I went through the troubleshooting manual and a little lost. The transmission relay was swapped out as it looked to be in terrible condition.

-Giuseppe-
1993 HMMWV M1025 A2 GMV Variant

 

[NDT]

Are you saying the transmission warning light is ON while the ignition is OFF? The transmission controller should be unpowered when the ignition is off. Suggest you still have issues in the relay area.

 

[Mariner]

Are you saying the transmission warning light is ON while the ignition is OFF? The transmission controller should be unpowered when the ignition is off. Suggest you still have issues in the relay area.

Yeh its strange that it comes on when the ignition is off.

So comes on when it goes to run, when I'm waiting for the glow plugs to warm up, turns off when running, and turns back on when I switch the ignition off. It will only stay off when I turn the batteries to off (installed a battery disconnect switch instead of a keyed ignition.)

 

[NDT]

Suggest you carefully verify all the connections associated with the transmission power relay. Maybe the controller is powered off with the ignition on and on with the ignition off. Also, the STE/ICE will not help you with this issue, it only provides very basic engine diagnostics such as fuel pressure and starter amp draw.

 

[Retiredwarhorses]

These codes are all standard GM codes, just Google DTC 53 on 4L80e…

 

[Mogman]

Are you saying the transmission warning light is ON while the ignition is OFF? The transmission controller should be unpowered when the ignition is off. Suggest you still have issues in the relay area.

Actually the TCM is powered all the time on pin Z, it has a run power feed also.

But the light should only have power in the run position.

 

[Milcommoguy]

Actually the TCM is powered all the time on pin Z, it has a run power feed also.
View attachment 882597
But the light should only have power in the run position.

That pictorial of the transmission power feed ... is or could be a bit confusing to a newbie to the lamp circuit. The ground on pin U to controller is a logic control "pull to ground or low" from the CPU.

This link below is a very good trouble guide with detail., wire numbers too. IMO a MUST have for 4l80e rig owners.

https://gear-report.com/wp-content/uploads/2017/03/Supplement_7_4L80E-Transmission_Troubleshooting.pdf

The more you know... the more you GO , CAMO

 

[Mariner]

Found the wire for the 12v side on the rear battery was connected to the forward battery. Swapped and the over voltage code cleared. Now I have codes 63 and 83. Has anyone seen this code 63? I cannot find it in the manual, and I triple checked it flashed code 63 as well. The lamp indicator dims but stays on when in off. Not a big issue as I have a battery disconnect in the meantime.

 

[AAVP7]

If the "trans" light stays on when the "run" switch is off (even dim), then something electrically is very wrong. I would go over the whole wiring, and check if everything is connected as it belongs, before I switch that TCM on again. Just relying on the battery disconnect doesn´t solve the apparent electrical problem.

Code 63 isn´t in the manual indeed. Google gave me " DTC 63 – Accelerator Pedal Position 3 Circuit High", but that´s from a civilian manual. Depending on which pole of the forward battery the 12 V wire was fixed, it could well be that the TCM was fed 24 volts.

 

[TOBASH]

Your protective control box PCB may be leaking green smoke. Might be time to replace if current continues to flow to tranny when you’re off. (I’ve heard of this before.) Either that or your ignition switch is defective (especially if you have an aftermarket keyed ignition). Or it could be both.

PM me if you need an EESS / PCB rebuild.

I sell a “Genius Box” because “smart boxes ain’t smart and don’t always start”. I also posted DIY instructions if you feel so inclined.

How to bypass PCB? I am aware some HMMWV owners have done it. TOBASH

I'm not trying to speak sacrilege here, and I don't want to precipitate a war of words. :shock: How might I build a manual control box? My 24Volt Landcruiser just uses a glow wire to show glow plugs are ready, and then she just starts right up with the twist of a key. Civilian 6.2 Diesel...

www.steelsoldiers.com

 

[Mogman]

Does the trans shift correctly? sending 24V to the TCM is never a good thing, I would suspect the smoke has been let out of the TCM

 

[Mariner]

I’m going to take it for a test drive tomorrow. To see if it now shifts correctly. Only code I have is a Code 63 from the transmission flashing light. Other than the normal start 12 and end 12 flash. I’ll check the connections on the ignition switch. Still using the factory ones.

 

[Mariner]

All codes are clear, code 63 was triggered by a little bit of transmission fluid in the Transmission Connector. Cleaned out and shifting with no issues. Still working on the transmission light being on. Funny thing is, when its off and you hit the breaks... the transmission light gets brighter and goes dim again when you release the break.