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My 2014 Promaster 148k miles 1500 all of a sudden, only shifts into park, neutral, 1st and reverse
almost seems like in a limp mode
any ideas?
 

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That is the definition of limp mode. It’s actually in second and reverse. About 35mph is to speed.
Many things can cause this, not just transmission related things. You’re going to need to read the codes. Autozone can do this for free if you dont have a reader.
 

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That is the definition of limp mode. It’s actually in second and reverse. About 35mph is to speed.
Many things can cause this, not just transmission related things. You’re going to need to read the codes. Autozone can do this for free if you dont have a reader.
 

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Weird. 2 codes are coolant related, thevrest are transmission.
There’s an amount of guesswork here because those tranny codes will mean a lot to a guy who works on transmissions all day, and less to me since I dont. But I can make the following suggestions in order of easiness

1. Inspect the big 20 pin plug the goes right into the upper transmission pan. It’s right in the path of road debris. Loose plug or damaged wiring here would cause those codes.
2. Check the fluid. Search this forum for transmission checking and you’ll find threads on how. The level is probably ok since the computer can throw a fluid level code. But the fluid could look dark, or smell burnt. That would indicate physical internal problems in the trans.
3. Take it to a trans shop and ask him to read the codes and diagnose it, but be preparred for him to say “you need a transmission rebuild” because that’s what ALL trans shop say about everything. But it would be helpful if be physically read the actual line pressure.
The last bits of advice are hail marys. Pull the lower cover and put in a new filter. A clogged filter could cause those codes. If it turns out to be the filter then you are still in trouble, because something made the filter clog. But changing it is cheap.
The last step would be a hail mary on the solenoid pack. It’s a $200 part, but it’s 75% of everything the trans does. It’s something you can install yourself if you have a few skills. I’d consider doing that as the last step before a rebuild/replace. I also mention it because replacing the solenoid pack saved me once, after having the same random limp problem you did. That story of driving 60 miles home on the highway at 25mph is on this board somewhere.

A question i’d be looking for an answer to is are the coolant codes related to the trans codes or indepent of them. Could running at low temperature induce transmission codes. Is it actually underheating and if so why. It the fan relay code is accurate, and the fan is stuck on,could running cold generate trans codes? I dont know, but I want to know.
 

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2014 Ram Promaster 2500 159" diesel
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The p1745 code is informational for the tech Your transmission is operating in open loop line pressure for 2000 miles or 1000 2-3 upshifts. Tranny not designed to operate in open-loop for extended period.
To erase the DTC you need to reset the VLP shift counter and the output tooth counter. You need a Micro pod II clone. Look under misc. functions for "Clear Variable Line Pressure (VLP) counters". Doing this should allow you to drive home but is not a fix it only resets the counters until they hit the limits again. Not good long term.
 

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Fix in this order. The flow charts have to many variables to list for a sure fire fix.
B0201 could be system voltage low

P0482 P0482-COOLING FAN 3 CONTROL CIRCUIT

P0128 P0128-THERMOSTAT RATIONALITY

P0420 CATALYST EFFICIENCY (BANK 1)

P1745 LIMP MODE "Clear Variable Line Pressure (VLP) counters".
 

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The P0420 is a cat code and wont affect anything other than lighting the light. I know this be because it’s been on for years in all my vans.
 

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Though you may be correct about the system voltage, I have found that the battery light is pretty accurate. If it’s below 13v or so when running, the light will be lit.
Then again, it’s B (body) code. I suppose it’s possible to have low voltage in the body control module, but normal voltage elsewhere. Dunno.
 

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The P0420 is a cat code and wont affect anything other than lighting the light. I know this be because it’s been on for years in all my vans.
Unless your in a state that does emission tests.
Some things that could cause it to light.
O2 SENSOR 1/1 RETURN CIRCUIT SHORTED TO GROUND
O2 SENSOR 1/2 RETURN CIRCUIT SHORTED TO GROUND
O2 SENSOR 1/1 RETURN CIRCUIT OPEN
O2 SENSOR 1/2 RETURN CIRCUIT OPEN
EXHAUST LEAK
ENGINE MECHANICAL CONDITION
AGING O2 SENSOR
CATALYTIC CONVERTER
 

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Though you may be correct about the system voltage, I have found that the battery light is pretty accurate. If it’s below 13v or so when running, the light will be lit.
Then again, it’s B (body) code. I suppose it’s possible to have low voltage in the body control module, but normal voltage elsewhere. Dunno.
I found one( b 0201a ) code in a promaster list and that is what it said. But early procedures and fixes are some times wrong in the books. Some B codes for Rams include A/C and A/C could be a fan problem.
 
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