So I've come to the almighty moparman forums seeking help on an unusual issue I'm having. My truck is heavily modified by the previous owner and I'm constantly having to fix one thing or another and chase things.

So I have 2 issues now 1 of which I believe I know the issue but don't know a good fix.

First issue is I get trans limp mode and a P1689 with no buss on the CCD when turning on the HVAC blower at any speed. Once turned off it goes back to normal. I have taken the ground off for the HVAC controls and the no buss issue also happens without the blower motor running only in face vents or floor vents position.

Looking at wiring diagrams I can't tell where any of the HVAC would cross with CCD modules.

Second issue I'm having is TCC lockup. I have increased line pressures and a DTT box to decrease the voltage to 4.5v all the time. It engages sometimes but not others and the only way I can tell is just by RPM at 60mph. It's 1 tick below 2000rpm with 4.10 ratio rear. I believe maybe the DTT box is bad or the line pressures are too high? What is the TCC lock up algorithm? Sometimes if I left off the pedal and slowly accelerate it will be locked. It's easier to tell if it's locked when I'm towing which is what I use the truck for.

Thank you for any help! I'll provide any info y'all need and hopefully I can get this all figured out!

Edit* forgot to mention I have done the following things to try to fix both issues.

PCM grounded to pass side battery negative

W-T mod

New batteries and alternator

Disconnected a/c relay and compressor( didn't fix so I guess it's not in the a/c circuit)

Edited Friday at 05:25 PM3 days by ducktape11
Added info

UPDATE

Did the APPS reset and didn't change anything. It reads 0-100%. It is not very fluid though it jumps but like 7% at a time going up and down. Is is supposed to do that? Also is the INJ pump voltage supposed to be 12v or bat voltage?

Driving around I couldn't get the TCC lockup unless I left off the accelerator to the RPM where it should be with TC locked then push back into it. After that it stays locked at all speeds even if I have to slow down and speed up as long as I stay in 4th. If I slow down enough for 3rd then I have to do it all over again in 4th. This leads me to believe it's a line pressure issue of not being enough?? I have messed with the pressures before but until today I haven't actually tested what they are. Once my gauge setup gets here today I'll get the hard data and drop the pan.

Might actually do pressure gauge testing to see where your transmission pressures are at. All the pressure test ports and pressures are in the Dodge FSM.

On 4/18/2025 at 9:52 AM, ducktape11 said:

First issue is I get trans limp mode and a P1689 with no buss on the CCD when turning on the HVAC blower at any speed. Once turned off it goes back to normal. I have taken the ground off for the HVAC controls and the no buss issue also happens without the blower motor running only in face vents or floor vents position.

I suspect that you may have a poor body to frame ground, or poor body to battery ground. Since the blower motor switch grounding and the data link grounding are in the body ground circuit, a poor body to frame or body / frame to battery ground connection could influence the CCD circuit. Body ground # 200 (located on the driver side inside the cabin) and engine ground # 107 are part of the CCD circuit.

You could temporarily run a jumper cable from the body directly to the battery ground post and then operate the HVAC blower fan to see if the symptoms go away.

• John