Hello,
I'm experiencing the same issue with a 2009 FEH. P0A7C triggers at 70+MPH REV 3k+. Did anyone figured out a solution? I will be checking the transmission pump, and may replace along the dc to dc converter.
Any tests or PIDs that i should be running/monitoring in forscan to help troubleshoot?

Looking a bit further, I also found Code: B12B8 - Driver Blend Door Actuator, Slow or Door Obstructed which also brings in the wrench light and few people experience the same symptoms, light coming in after 1 hour, 70+ MPG, RPM 3k+. I will change the blend door actuator and will report here.

Thanks im advance

 

Aaaaallright, hello everyone. I am jumping back into my own P0A7C odyssey (2012 AWD limited) and got bounced over here from Escape City forums. Seems like an increasing number of higher mileage 1st/2nd gen FEHs are having this issue and I’ve yet to see a real solution. I may try to start a definitive thread but for now I’ll pick up here with what I know so far:

• My issue started a few years ago, something like 90k miles (currently 110k)
• started on the Grapevine here in CA (eater of cooling systems) on a hot day

• seems only to arise on sustained climbs in warm weather (temp-dependent)
• 90ºF or hotter outside temps have triggered this issue on level freeway (70mph +) …happened maybe twice
• Only illuminates wrench light in my case (no SSN, no electric powertrain behavioral differences)
• Light is cleared with restart (forscan still shows for a while but “DTC not present…”)
• Both Coil, phase, TFT, MECS coolant, and battery temps are within reason and vary when DTC trips (there doesn’t seem to be a threshold for any of these)
  • last few times the MECS coolant temp was, if anything, low (40ish C)
• GenCoil temps stay within 10-15ºC of TFT unless climbing, then around 20ºC
• TFT temp tends to climb gradually @ freeway speeds….suggests cooling issues
• DTC trips with or without A/C on
• DC-DC converter housing warm but not hot to the touch at time of DTC
• sensor tripping the DTC seems to be a threshold-type, cannot find which it is, where it is, or if it can produce discrete (temp) readout

Things I’ve tried:

• MECS pump replacement - no effect (my 2012 already had the remedied pump and it was functioning upon removal)
• MECS coolant vacuum fill (after pump replacement, performed @ Ford service by request) - no effect
• A/C recharge (refrigerant was low suggesting slow leak, but my 2012 uses cabin air for battery cooling without refrigerant lines that I am aware of) …no effect
• 12v battery replacement (sort of incidentally as I’ve had 2 die on me…no apparent affect on hill-climbing wrench light)

After reading through this and a variety of other threads on several forums, I am left with the following questions:

Q: Has anyone seen any single indication of a solution or remedy for P0A7C errors in any thread anywhere?

Q: Did PCM replacement have any effect (hadn’t thought of the reference voltage thing)

Q: Did DC-DC converter replacement have any effect? Were there any other symptoms to suggest that module was problematic?

Q: Did the trans-cooler retrofit have any effect on either the error codes or TFT - I would be interested if this even just established a reliable thermal equilibrium as my TFT seems to have no clear top end at highway speeds

Theories: mostly centered on things that might gradually change over the life of the vehicle, to explain the late onset:

1. MECS issues: though it might be the infamous MECS pump despite having the last model year, but sorta ruled that out after shotgun replacing it and having a vacuum fill to theoretically eliminate air pockets…..in retrospect I don’t have much faith that Ford service did that procedure correctly and am again suspicious that there’s an air trap in the inverter housing, given the bleeder there.
2. Tired traction battery: I had thought perhaps an aging pack might be demanding more current to stay above min charge levels, putting more load on MG1 while it’s already working to keep MG2 running at highway speeds, but I’ve had no other battery symptoms, temps all seem mostly ok, and i’d kinda expect this to have gotten worse over a few years of continued driving.
3. Inadequate transaxle cooling: Given my observations of transmission fluid temps rising without a clear top end on the highway, I wondered if there’s just enough heat build-up int here to soak into the inverter electronics and trip a sensor somewhere in there, but I cannot explain why this wasn’t an issue from the start (definitely USED to be able to climb mountain passes without error lights
4. Bad sensor: this would be easy to confirm if I had any idea what is actually tripping the DTC and where it is….no idea if this is a replaceable part. The clear exterior temp trends (only a problem in hot weather) and late onset of the problem don’t support this very well…but I’d still like to know where exactly the problem is originating if anyone has ideas

Next Steps: I bought a vacuum fill kit (much cheaper than ford’s service charge; if you have a compressor already, take note) and over the long weekend I have a few things planned...

1. Open the bleeder on the inverter. I am curious to see if I get air or coolant (was afraid to do this before changing fluid anyway for fear of introducing MORE air)
2. Vacuum fill MECS coolant
3. Vacuum fill Engine coolant (these two systems are connect, btw….ford tech mentioned that and I didn’t believe it until I saw the clearly different coolant (orange no longer made) mix between the two bottles over time)
4. Change transaxle fluid - leaning toward Valvoline’s Hybrid-specific full synthetic (recs welome)
5. change PTU fluid

If I still get errors after all that, I will look into changing the DC-DC inverter (stabbing in the dark) and possibly doing an external trans cooler retrofit since there seems to be a mounting location for the oil cooler the V6 is equipped with?

I have some other maintenance and upgrade work waiting on this now; I’d planned to get this vehicle to 200k or so but don’t really want to throw money at anything else until I get some indication this temp issue is either solvable or not a real concern. I have hills to climb.

If you are or were having this issue, please chime in whether or not if you’ve solved it yet.

(PS- this forum is really good at throwing away drafts

 

Thanks for hauling this topic back up, Escape from LA (great handle!)
Q: What vacuum fill kit are you using? I need to get one.
I'm bringing my recently acquired FEH up to daily use standards and am next going to be working of the cooling system (no issues currently)
Changed the engine oil to SuperTech High mileage Synthetic right after I got it running.
I just changed the Transaxle oil to the Valvoline Hybrid syn ATF product.
Considering that the eCVT system is virtually identical among several manufacturers that factory fill them with multi-use ATF of their own (WS, LV, etc) I decided that the full synthetic Valvoline would be a fine replacement. The temp range of synthetic ATF is a big plus to me.
Mine is now over 215k miles and drives nicely with no faults other than the dang Tire pressure sensors and the rear glass ajar fault.
Brought this back from a "brick" that has sat for months and would not start.
Original HVB as far as I can tell. Recharged over a few hours, now seems to be fully operational.
My Sync readout shows 35+ mpg now.
Here is a link to my Intro here a few weeks ago
Danny near Mt. Rainier

 

Cool...grew up in WA. Using ....looks alright (haven't gotten to the fill yet)

I wound up working on everyone's projects but my own over the long weekend but today I did finally go after that bleeder bolt in the top of the inverter housing...which they did NOT make easy to get to (just barely 2 clicks worth of movement allowed after snaking my socket wrench in past the wiring and vacuum line). Learned a few things, but nothing hopeful:

• It's a short bolt (yes I dropped it) and it doesn't seem to allow any seepage before coming completely out.
• If there was any air, I didn't see or hear it
• It's a good bit lower than the catch bottle so it will drain the bottle if you let it go....quickly (pretty unrestricted flow)

...And that was without the pump running. I closed it, topped the bottle back up, ran the pump for a bit (key on), then bled a little more (you're gonna want latex type gloves for this..kinda have to do it by Braille). I may take it for a drive tomorrow but I doubt there is any major change; I'd be more optimistic if there'd been signs of air/sputtering/anything other than the clear laminar flow I saw streaming out of that bleeder port.

I have everything ready for full drain/flush/vacuum fill and hope to get through that in the next few days...after which I will do some mountain testing, and will be satisfied that if the issue persists, it's not the actual MECS loop itself.

That would leave me at Tired Traction Battery (in which case I'd kinda expect to see the MG1 coil and phase temps climb on direct readout) or maybe this PCM theory and/or faulty sensor(s)....

I do see one grey harness with 2 leads on the DC-DC converter (just below the 12V output) that I wonder if might be a replaceable temp sensor, but I have read a few reports of people shotgunning new DC-DC converters in with none of them solving the issue. There is one other replaceable temp sensor on the transaxle that I looked into before and deemed ok, but it might be worth replacing that just to confidently eliminate the problem source. No sure if/where there are other replaceable sensors...all ears if you know

 

Hi everyone. Chiming in as another FEH (2009) owner experiencing the same P0A7C issue w/ the yellow wrench light. Like many of you, this happens after about 45 minutes or so of driving on the highway. Today I tried driving with AC on and the light appeared at 45 minutes. On the way back, I drove without AC and the light appeared at 1 hour and 20 minutes, although a good part of the first 50 minutes was a lot of traffic on the highway and when I started driving a consistent 70 MPH, the light finally appeared at the 1 hour 20 minute mark.

When I first brought my FEH to the mechanic, the mechanic noted that the MECS pump wasn't functioning properly and replaced that, and mentioned I might need an ECU reprogram (which I didn't get). The problem didn't go away. He then mentioned the DC-DC inverter/converter, which I didn't change yet as I didn't want to keep replacing things on a hunch.

I notice when I the P0A7C code showed up, I also got a P0562-FF (System Voltage Low) so wondering if anyone else got that.

Reading through this thread, it sounds like we haven't found a definitive root cause. However, it's comforting to be in a community of folks experiencing the same problem. Doesn't seem like Ford's diagnosed this themselves and issued a TSB for this problem.

One question I'd like to ask others is that my FEV has 100k miles. It sounds like others with the problem have driven for many miles after first experiencing the problem. Could you tell me how many miles you've driven so far with this issue and have you noticed no negative impact on the health or performance of your FEV?

 

I've got 115k on mine and this problem started just shy of 100k if I recall correctly.... have yet to find any lasting effects or really any material issue at all. It has gotten progressively easier to set off the wrench light over that time; what first popped up in 90 degree weather climbing the grapevine will now occur in the 70s and occasionally on level ground....so it seems to getting more sensitive.

Since making sure the MECS system was fully bled, I've gotten one closely-monitored climb in....wrench lit up as usual (now) but also some new behavior: traction control error. After pulling to an offramp for cooldown (stopped, ignition on for running MECS pump)...I cycled the ignition to clear the wrench light and started to pull away slowly, only to have ABS activate (BRRRRR) and traction control light briefly, then light up both lamps (swerve-looking engagement light and TC-off) and stay lit. This was level ground and there was no wheel slippage. Reset the module, and had no more problems until exactly the same thing occurred maybe a 30 minutes later after another steep section lit up the wrench again. Same sequence...cooldown stop, ignition cycle, slow accel activates traction control interference; ABS and power limiting, then lamps stay lit until reset. No issues since.

...this may put PCM at the top of my suspect list. I am under the impression that is what is reading wheel speed sensors (tone rings) but, not being a mechanic, am not clear on what falls under PCM vs another module. I have spark plugs and the inexplicably-hard-to-reach cabin air filter to replace one of these evenings, so I think i might pull that module, open it up to look for anything obvious (corrosion, signs of heat), clean contacts, and reseat all the connectors.

Other observations from this round

• warmest reading was Generator Coil Temps but varied 87-92ºF 87ºC)
- Trans fluid (TFT) in the mid 70s, Motor Electronics Coolant Temp (MECT) in the mid 30s,
• Traction battery voltage 315-330V (not as low as I had feared might demand excess charger current from MG1)
• Both outer housings for the DC-DC convertor and motor inverter(s) were cool enough to hold a hand on this last time the wrench lit up....the DC-DC especially so (I would call it warm rather than hot) so that unit remains low on my suspect list.
• Still no indication of the specific source for this code....ForScan-monitored temps differed some for several of these last occurrences


So...PCM seems to need investigation and I need to do homework on which modules were involved in that traction control issue.

If I get nowhere there, it'll be back to the MECS loop, since the higher cruising speed and indicated TFT in the 70s suggest marginal cooling efficacy in that inverter housing atop the transaxle.
• Decided its worth replacing the coolant sensor in the inverter housing; waiting on that for a full coolant change (since its removal opens the loop)
• thinking a more thorough flush is probably in order, since a low MECS flow rate would explain a lot (particularly given low reported MECT at time of DTC)

Then I guess it's battery time...a degraded traction battery would fit the number of people experiencing this at higher mileages, but unless I can figure a better way to monitor the charging demand it's placing on the system, it might end up being a "needed to happen eventually anyway" refurb/replacement.

 

Thanks for the break down of items to check. My 2009 FEH started having the same issue on a trip from Cincinnati to Pittsburg and back. It seems that the safest, easiest, low cost next step is to verify that the MECS pumps is working and change the eCVT fluid and flush/replace the MECS coolant. Should I run coolant cleaner / flush a bit before changing the coolant?

 

@EscapeFromLA You ever figure out the root cause of your P0A7C?

 

Still working on it....between work and getting rear-ended last week , I haven't had time to get back into it.

 

Sorry to hear about the rear-end! I'm wondering if anyone on this thread has looked into whether the cooling system from the outside air (leading from the rear window intake on the driver side) has gotten clogged or if there's a fan that's used to cool the hybrid batter.
I chatted with a mechanic and he asked if I had a dog, speculating that perhaps dog fur could get trapped into the air ducts. He also mentioned something about a fan for the battery.