Power train warning and loss of power / acceleration

[tradwich]

I have a 2017 Navigator L. The other day while driving, I lost the ability to accelerate while the vehicle was in motion. The power train warning light (a wrench symbol) came on. The car shifted down and it slowed pretty quickly on a busy street. I pulled over, turned the car off, restarted it, and I've been able to drive it. Spoke with the dealership today, they have no idea where to start diagnostics. Anyone else have this happen to them?

 

[Action]

The place to start is pulling the DT codes. There may not be an active code and the event will be in the history, unless the history was cleared, the battery was disconnected for 20 minutes or more or enough start stop cycles have occurred. (This varies on vehicles form 20 to 89 cycles)

The event you described is the vehicle going into limp mode because the PCM was reacting to input that engine damage was possible by continued operation. The typical issues are over engine heating (not necessarily coolant over heating and/or loss of oil pressure)

When the engine is off, do check fluid levels.

How many miles on the vehicle?

Action

 

[CruiseGuy24]

Interesting you post this now. I have a 2019 and on Monday I was on the highway and got a similar message about a powertrain failure and that it was operating at reduced power. Had the wrench light on and trans was shifting hard and erratically. After I pulled over and turned off/on again the error was gone. I have not had a problem since. Called dealer to setup appointment and while on the phone she saw the error and a bunch more that I could not see. She said some related to Turbo and battery. Mine goes in late next week so will see what they find.

 

[tradwich]

The place to start is pulling the DT codes. There may not be an active code and the event will be in the history, unless the history was cleared, the battery was disconnected for 20 minutes or more or enough start stop cycles have occurred. (This varies on vehicles form 20 to 89 cycles)

The event you described is the vehicle going into limp mode because the PCM was reacting to input that engine damage was possible by continued operation. The typical issues are over engine heating (not necessarily coolant over heating and/or loss of oil pressure)

When the engine is off, do check fluid levels.

How many miles on the vehicle?

Action

Thank you for the reply.

About 65K miles.

The coolant level was low, that was about it.

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[Action]

If it were my Navigator, I would have the DT codes pulled. Don;t have a reader? No problem (assuming you are in the US) Go to a fast moving parts store (Auto Zone, O'Reillys or ???) and they will pull codes for free. Post back with the result.

If the PCM moved the engine controls into the LIMP Mode, it would have done this as a precaution. Think about this a little bit. The previous engine in Navigator displaced 5.4l and put out 310 HP. Your engine is 3.5l and puts out 380HP.
That is 70 more HP with 1.9l less engine displacement!
This means every bit of the smaller engine is working harder all of the time to do a bigger job.
And leaves little room for errors or issues.
So the PCM is going to be sensitive to sensed threats to engine health.

Because of that my opinion on coolant changes,
For your 2017 the maintenance schedule for the coolant is
Initial replacement at six years or 100000 mi, then every three years or 50000 mi
In my opinion draining and refilling coolant every 30,000 to 50,000 miles would be what I am doing.

Low coolant generally means it is leaking somewhere. The system is sealed when the cap is properly closed.
Before I changed coolant I would have it pressure tested. And tested to a PSI several higher than the cap is rated. Do have the cap tested too.
And if you are driving it now make sure the coolant level is topped off at least with water.
And water is all I would use if you are going to do a drain and refill soon.

I have a similar issue going on. However, I know I have a pinhole leak in a heater hose. For now, I am waiting for the outside temperatures to drop below 80 to do the job. Phoenix is still flirting with triple digit highs

Action

 

[tradwich]

The place to start is pulling the DT codes. There may not be an active code and the event will be in the history, unless the history was cleared, the battery was disconnected for 20 minutes or more or enough start stop cycles have occurred. (This varies on vehicles form 20 to 89 cycles)

The event you described is the vehicle going into limp mode because the PCM was reacting to input that engine damage was possible by continued operation. The typical issues are over engine heating (not necessarily coolant over heating and/or loss of oil pressure)

When the engine is off, do check fluid levels.

How many miles on the vehicle?

Action

Update: Resolved — It ended up being the throttle body assembly. I had it replaced and it’s running again fine.

 

[tradwich]

Interesting you post this now. I have a 2019 and on Monday I was on the highway and got a similar message about a powertrain failure and that it was operating at reduced power. Had the wrench light on and trans was shifting hard and erratically. After I pulled over and turned off/on again the error was gone. I have not had a problem since. Called dealer to setup appointment and while on the phone she saw the error and a bunch more that I could not see. She said some related to Turbo and battery. Mine goes in late next week so will see what they find.

Hey just a quick update — It ended up being the throttle body assembly. I had it replaced and it’s running again fine.

 

[CruiseGuy24]

Thanks for the update. My similar issue ended up being a bad mass airflow sensor.

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[Psykostevo]

I have had this same issue happen twice in the past month, once when towing and once when not towing, both when driving at a steady speed around 55-60mph or so. Took it to the dealer yesterday and they noted that I still have the original battery, and that they may need to replace it when I bring it back in for service to have the front star replaced on the grille.
Got me wondering now if it could be a bad or even dirty throttle body. Maybe I will pull the intake tube off and check the blade to see if it is just dirty or something in the meantime.

 

[Action]

Got me wondering now if it could be a bad or even dirty throttle body. Maybe I will pull the intake tube off and check the blade to see if it is just dirty or something in the meantime.

That is an issue for electronic throttle bodies. If enough debris gets into the throttle plate area the assembly can stick, causing the electric motor to strain. That and poor electrical connections.

More frequent changing of oil/filter and air filter can help. Along with any crankcase vent system servicing.

Action

 

[Psykostevo]

That is an issue for electronic throttle bodies. If enough debris gets into the throttle plate area the assembly can stick, causing the electric motor to strain. That and poor electrical connections.

More frequent changing of oil/filter and air filter can help. Along with any crankcase vent system servicing.

Action

It also can be caused from excessive oil residue getting recirculated through the intake from the PCV system, and cause the Throttle Body to get glazed, and then possibly also dirty from debris sticking to the oil residue. Once you have enough dirt on the blade, it can cause issues with the rate of opening and closing compared to the computer's expected values, and when there is a mismatch it can throw a code due to a correlation issue.
That's why I was thinking it might be worth my time to pop the TB off and clean it.
I watched some YouTube videos on replacing the TB, and it seems that the 4 bolts holding it in are tight as heck from the factory, and I can confirm after half heartedly putting a socket wrench on them that they are in fact tight as can be. Also saw some people have issues with vacuum leaks after trying to replace their TB so that had me take a pause for now at looking further into it, as I would hate to make my issue worse through good intentions.

 

[vrice41]

My 2017 nav did it yesterday, leed frame senior in transmission?? Started back up drove home . Not driving anymore. Taking to dealer.

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[vrice41]

My 2017 nav did it yesterday, leed frame senior in transmission?? Started back up drove home . Not driving anymore. Taking to dealer.

Oil life 43%

 

[G-42817]

Oil life 43%

Throttle Body

 

[dlcorbett]

Man this thread was made about 3 months before I bought my navigator. My navigator starting doing this in April of 2023, and it would only do this on long road trips in really moist conditions. I took it to the dealer multiple times, had turbos replaced, transmission reflashed, some sensor replaced, and even replaced coolant hoses and thermostat, and no fix. If I knew about this thread, I wouldve brought the throttle body up to their attention. Eventually, I just stopped putting it in eco mode, and stopped having the issue until I lost the car. Still hurts btw, i miss her dearly.