P0A7C criteria PCM parameter / wrench light?

[wr400f250]

The TSB was performed along with a warranty repair a few years ago. It was done at no extra charge if I remember right, since they were going to be plugged into the computer anyway.

[Jrpavv]

I just called my dealer to see how much it would be for the TSB, which calls for 0.3 hours. Told me $150

[calihybrid]

Has anyone made any progress on this issue? I'm having the same problem with my 2011 Escape Hybrid Limited - wrench comes on after approx 1.5 hours of driving at 70mph+ in ambient temps above 80 degrees. So far I've had the MECS pump replaced (this seems to have stopped the SSN events, but I still get POA7C), the system bled 3 times, and the transmission temp sensor replaced, none of which alleviated the problem. I've also been monitoring temp levels of MECS coolant, transmission, generator, and inverter, and nothing is going over spec.

A hybrid garage nearby has suggested cleaning the battery cooling fan, although I think that's generic advice related to the Gen 1 Escapes. Ford dealership suggests replacing the MECS radiator, but they are just as befuddled as we all are at this problem.

[wr400f250]

The Escape has a somewhat different (and in my opinion, better designed) cooling system than the Fusion, as well as a slightly different transaxle/inverter setup. Our 2009 Escape Hybrid doesn't have this issue, so when I get a chance I'll look at the numbers and see what temperatures are "normal" for the system. The major difference is ours has a mechanical A/C compressor, 2010-2012 Escapes have an electric compressor like the Fusion.

This issue seems to be much more common on the Fusion, but has me curious which parts are shared between the two as that might narrow down the search somewhat.

I probably won't be able to check anything until summer. As far as I can tell, the only procedure that hasn't been done yet here is to vacuum-fill the cooling system. This would eliminate the possibility of air being the issue, and is still #1 on my to-do list.

[Jasonisawesome]

So I'm having an identical issue with my 09 ford escape hybrid that I picked up at auction with 116k on it.

I replaced the MCES pump, the transmission fluid, the transmission temperature sensor, the transmission temperature sensor harness, and bled the system.

It's like clockwork the wrench light comes in and gives me an overtemp error code even though there are no drive ability issues, and all the temperatures are within spec


I'm going to call the dealership and see if they can update my PCM to see if that helps, it's been a struggle trying to decipher why the wrench keeps coming on.

[wr400f250]

Jasonisawesome, which code exactly are you getting with your Escape?

[tim0574]

Can anyone give me the temp specs because I can't find them. I've seen references in a fusion forum that put 140° to 150° in the concerning range for the electronics and the reason why there's a separate cooling system.

I have a 2011 with the same code coming up more often even when it was 25° out the other day. I had forscan light on a tablet with a USB adapter to monitor everything.

Previous runs had me concerned about the generator inverter because it had spiked high near the wrench light trigger. But mecs coolant temp is very low and those inverter temperatures drop quickly after spikes. The temperature control from the orange coolant seems to be fine across those temp sensors.

During my sustained highway driving the other day the things that concerned me are the generator coil, motor coil and transmission fluid temps. They kept steadily building the longer I maintained the drive. Both the generator and motor coil temps got into the 160s. Transmission fluid got into the 130s and all of them move down very slowly when speed was decreased. During the drive the main motor coolant temp got to 180 which isn't abnormal.

But other than engine coolant I'm not sure what these other temps should be. In one of the Weber Auto videos he mentions if the transmission fluid gets too hot that it could melt the coating off the electric motor windings.

What I'm thinking about now as a theory is if the transmission electric fluid pump is not working correctly or at all to move the fluid through the radiator for proper air cooling.

[tim0574]

Alright, I think I'm definitely off on the last idea as I understand it, the trans oil is pumped mechanically off the generator shaft.

[wr400f250]

Tim, the symptoms you describe exactly match those I saw going from CA to AZ and back. Zero issues until the transmission fluid (not MECS coolant) warmed up as evidenced by coil temperatures. You are correct that the trans fluid is pumped mechanically, a system which is not likely to fail.

I did notice that the 2013-up Fusion Hybrid added a transmission fluid cooler. On our 2012-down hybrids, trans fluid is cooled exclusively through some small fins on the bottom of the transmission housing itself. MECS coolant probably helps somewhat via heat conduction through the housing, but is primarily intended to cool the inverters.

My theory at this point is that the higher transmission fluid temperatures on sustained drives cause increased resistance in the generator coils. This works the generator inverter much harder as it tries to maintain battery level as well as engine RPM.

The generator inverter also sits at the very top of the MECS cooling system, with the bleed screw all the way on the other side of the engine bay at the DCDC converter. This means any air in the system will eventually collect at the inverter if it can't escape through the reservoir. The presence of air at the inverter, combined with the increased resistance from the coils overpowers the inverter's ability to shed heat at high speeds. Either that, or the inverters are fried (not likely IMO).

How to fix it? Two options in my opinion.
- Option #1, Vacuum fill the MECS system. Make sure air can not enter the system by any means. Do this every 50-100K miles
- Option #2, Somehow figure out a way to add a transmission fluid cooler. Best idea I can think of is to use the fill and drain plugs, find a small electric pump, and send the fluid through a small heat exchanger by the radiator.

[Jasonisawesome]

Jasonisawesome, which code exactly are you getting with your Escape?

P0A7C:00-2B