Interesting PHEV Behavior Post-FORM/CCOH Repair

[ntravaglino]

Hey guys, thought I'd share an interesting behavior of the hybrid system after getting it back up-and-running properly. I'd be interested if anyone else has experienced this.

For starters, I encountered the FORM and CCOH errors that so many others have run into. I took delivery in April 2021, and the problem started in February 2022 at about 6000 miles. Service identified "7275 hightemp coolant pump failure" with code P0c74-00. After waiting for the part to arrive it was installed and the hyrbid system has been generally working well. The car starts up in electric mode and uses up the battery in hybrid mode until around 50% battery life is left or unless I mash the pedal. Then the ICE and electric motors alternate. This is consistent with operation prior to the first FORM/CCOH errors.

I drive the 4xe to/from work 26/33 miles each way most days. In the mornings the trip is shorter and slower (this is important). On the way home I take the highway and speeds are more like 70-75 MPH. This is where the interesting behavior comes in: On the way home, at highway speeds the electric motor operates from 100% to 30%. Then once I dip below 30% battery life, while under steady throttle, car speed declines to sub-60 MPH. and will maintain there until I mash the throttle or manually switch to e-Save from Hybrid mode. I can best describe the throttle response as being like a speed limiter/governer kicking in. I can usually get back into hybrid mode after a few minutes so it is no big deal, but it is different from prior behavior. Anyone else experiencing this?

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[mllcb42]

Have you checked your battery and electronics coolant levels? If I had to make a wild guess, I'd say that what you're experiencing is related to something in the system overheating due to the higher load from the high speed.

 

[DewHawk]

On the way home I take the highway and speeds are more like 70-75 MPH. This is where the interesting behavior comes in: On the way home, at highway speeds the electric motor operates from 100% to 30%. Then once I dip below 30% battery life, while under steady throttle, car speed declines to sub-60 MPH. and will maintain there until I mash the throttle or manually switch to e-Save from Hybrid mode. I can best describe the throttle response as being like a speed limiter/governer kicking in.

Just for the sake of clarity, are you rolling on bigger wheels/tires? Might help narrow down if yours is an isolated issue or if it’s more indicative of a load related problem.

 

[lindaspins]

I have experienced this twice in 10,000 miles. No obvious cause, it just bogged down then finally figured itself out.

 

[ntravaglino]

Just for the sake of clarity, are you rolling on bigger wheels/tires? Might help narrow down if yours is an isolated issue or if it’s more indicative of a load related problem.

Nope, stock JLUR 4xe

 

[ntravaglino]

Have you checked your battery and electronics coolant levels? If I had to make a wild guess, I'd say that what you're experiencing is related to something in the system overheating due to the higher load from the high speed.

Great thought. I’ll check that when I get a chance. *Should* have been checked/topped off according to the repair invoice but stranger things have happened and/or maybe there’s a leak that made the first pump go bad?

 

[ntravaglino]

I checked both coolant tanks and they are filled up to but not exceeding the Max Line. So it does not appear that a lack of coolant is the issue.

My understanding is that coolant temperature is regulated via the A/C unit, which is also battery powered, so even with 30% battery life the system should be OK. If it is indeed overheating at speed/higher power output then maybe the system just can't cool and circulate enough coolant to handle the load? Or the hybrid system should be switching to the ICE earlier/more frequently? Or maybe it isn't about temp at all? Who knows!

I'll come back here and post if I find anything else out.

 

[Echo4papa]

This happened to me twice... both times before the updates/RRTs. Once on the stock Sahara wheels and tires, and again on the 392 take offs. Both times within a week or two of each other. Both times I was driving at sustained higher speeds (70-75 mph), the ICE was not on, and I lost power slowly until me speed dropped down a bit and the ICE kicked on.

It's never happened again so my assumption was that I exceeded the parameters for running on electric only and whatever reason caused the ICE to not come on immediately was corrected with the RRTs but... that might not be the case.

The only way you may ever know for sure is to monitor the data points involved. There is some information on this floating around (here or on the 4xe forum, or might have been the 4xe FB group, I don't recall). If you familiarize yourself with what gets monitored by the system, track it yourself and compare those values when you experience the issue versus normal operation you might be able to see exactly what's happening.

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