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Engine Light coming on

Sardis333

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Hello there,

I just bought a brand new 2022 Ram back in December. So far the truck has been amazing! However I am getting an intermittent engine code during very specific conditions:

I am towing a trailer and have it set in "tow/haul" mode.

I have a load in the bed and I have it set in "tow/haul" mode.

When I decelerate from driving, the engine light pops on, I get a beep, the auto start/stop symbol lights up. When reading the code, it is U0402, the engine failed to communicate with the transmission.

It has been to the dealer once and they could not explain it. Has anyone experienced this or have any ideas what might be going on?

TIA
 

Fatherof3

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Sorry I don’t know anything about that code . Now what do you mean the dealer can’t explain it ? A check engine light is not normal operation . I would suggest taking it to another dealer and see if they’ll help .
 

petersen0550

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Mine did this yersterday, towing a trailer for the first time. 2200 miles on the truck. Only happens while in tow haul mode, first dealership couldn’t explain it. Sent me home, on the way I put it in tow haul mode and it went into limp mode, drove to new dealership and dropped it off. Can’t get it looked at until tuesday.
 

c3k

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Hello there,

I just bought a brand new 2022 Ram back in December. So far the truck has been amazing! However I am getting an intermittent engine code during very specific conditions:

I am towing a trailer and have it set in "tow/haul" mode.

I have a load in the bed and I have it set in "tow/haul" mode.

When I decelerate from driving, the engine light pops on, I get a beep, the auto start/stop symbol lights up. When reading the code, it is U0402, the engine failed to communicate with the transmission.

It has been to the dealer once and they could not explain it. Has anyone experienced this or have any ideas what might be going on?

TIA

That's not normal. Get it fixed. Is it going to be tough for the service department to troubleshoot? Yep, but that's their job.

I don't want to alarm you, but do not accept this. Each time it happens, bring it in. (In fact, I would repeat the conditions that cause it, as needed.) Each time they say "we can't figure it out", get it in writing on the service form. Then, use your state's lemon law.

While you're doing that (to protect your ~$50k investment), open up a case with Ramchat (or is it Ramcare?). There are links on this forum.
 

petersen0550

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Hello there,

I just bought a brand new 2022 Ram back in December. So far the truck has been amazing! However I am getting an intermittent engine code during very specific conditions:

I am towing a trailer and have it set in "tow/haul" mode.

I have a load in the bed and I have it set in "tow/haul" mode.

When I decelerate from driving, the engine light pops on, I get a beep, the auto start/stop symbol lights up. When reading the code, it is U0402, the engine failed to communicate with the transmission.

It has been to the dealer once and they could not explain it. Has anyone experienced this or have any ideas what might be going on?

TIA
Any word? I just got a call to pick mine up, they said it was a bad ground wire. I drove 1 mile, put it in tow/haul mode. Again, engine light and limp mode. This is now 3x for me in the shop for the same issue, one more time and I’m going to look into AZ lemon Law, sucks!
 

jmt8706

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Any word? I just got a call to pick mine up, they said it was a bad ground wire. I drove 1 mile, put it in tow/haul mode. Again, engine light and limp mode. This is now 3x for me in the shop for the same issue, one more time and I’m going to look into AZ lemon Law, sucks!
See if you can get a mechanic, or service writer to go for a ride with you , then you can duplicate the situation.
 

Sardis333

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I have mine scheduled for tomorrow to go in. Going to tak to the service advisor directly. I will let you know.

BTW, what part of AZ are you in? Curious as I am also in AZ
 

Sardis333

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Just finished up at the dealer. They went over it head to toe a couple of times and can't find anything. They are reaching out to their engineers. If I had to venture a guess at this point, it is a software glitch and the ecu needs a patch. Mechanically everything checks out.
 

gkostera

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Had same issue with my 2022. Apparently a TSB just came out on this a couple days ago. Dealer ship changed my PCM and still happens. It's apparently a software issue they are working on. Hopefully someone can find the TSB and post. It usually happens when you are in tow mode and I think auto stop is turned off.
 

Camel_City

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Exact same issue here. In T/H mode and seems to only happen when decelerating/braking. Check engine light comes on and truck goes into limp mode. Service department is just scratching their heads at this point. Other than an occasional black screen on the 12" radio, it's the only issue I've had, but for what I paid for this truck, the T/H issue is not acceptable. More to come ...
 

waveband1

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Exact same issue - 3rd time, pulling 22' travel trailer, exact same from our dealer as well- can't find anything wrong.. usually engine light disappears after we drop the trailer and restart engine, so no codes. -except- for this last time, yesterday 6/12/22. Engine light stayed on, so were making an appt with dealer and hopefully light reamins on, we will see. Video on Youtube suggested same problem, truck throwing error Code PO755 (Solenoid Circuit) - which they replaced but didn't fix the issue. Wife just text, looks like we have an appt to drop today 6/13.. will post findings.
 

Camel_City

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Exact same issue - 3rd time, pulling 22' travel trailer, exact same from our dealer as well- can't find anything wrong.. usually engine light disappears after we drop the trailer and restart engine, so no codes. -except- for this last time, yesterday 6/12/22. Engine light stayed on, so were making an appt with dealer and hopefully light reamins on, we will see. Video on Youtube suggested same problem, truck throwing error Code PO755 (Solenoid Circuit) - which they replaced but didn't fix the issue. Wife just text, looks like we have an appt to drop today 6/13.. will post findings.
Code U0402 (invalid data received from the transmission control module) is the one mine keeps throwing.
 

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