2013 Energi P2796 code on auxiliary transmission pump

[GSMacLean]

So back in December while out driving, my 2013 Energi, despite having almost a full battery charge, abruptly started running on its engine. Both EV modes were disabled (greyed out with an "X" through them) and the only option it gave me was "EV Later". Shortly afterwards, I got a check engine light.

 

When I got home, I pulled the codes, and got a P2796:00 - here's what the service manual has to say about this:

 

P2796:00

Electric Transmission Fluid Pump Control Circuit

This DTC sets when the E-pump is not receiving a signal on it's PWM input signal from the SOBDMC / TCM .

 

So the Energi has an auxiliary transmission fluid pump bolted to the outside of the transmission. Because the internal transmission fluid pump is driven from the engine, the car needs a way of circulating transmission fluid when it is running in EV mode, and the engine is not running.

 

This pump is controlled by the SOBDMC, which is that big computer box on the driver's side in the engine bay that controls the entire electric side of the car. The SOBDMC controls the pump's speed by sending a PWM (pulse-width modulated) signal. The pump sends back a signal of some kind to the SOBDMC to let it know that it is working. If the SOBDMC doesn't see the expected "hey I'm running OK" signal from the pump, it shuts down the electric side of the house and forces the car to run on the engine only, to avoid damaging the transmission by running it without lubrication. When this occurs, it throws code P2796.

 

So the Ford service manual has you pull the cable from the SOBDMC end and from the pump end, and check the wires to make sure there are no opens or shorts. I did so, everything checked out fine. I cleaned all the contacts and reseated everything. I took the car out for a test drive, and within a mile or so, it threw the same code again.

 

According to Ford, the next "diagnostic step" is to replace the SOBDMC. Uh, yeah. Not only are those things crazy expensive, the labor to replace them is crazy (there's all kinds of coolant circuits and hoses), and they have to be programmed to the car. I'm thinking perhaps the pump is at fault. Why Ford skips that possibility in the service manual, I have no idea.

 

So I pulled the connector at the pump end. There are 5 wires - unswitched +12v, switched +12v (ISP-R), the PWM control signal (TAPR_CT) from the SOBDMC and the diagnostic signal (TAPR_DI) to the SOBDMC. I put my scope on the PWM control signal, and using ForScan, commanded the AUX_TLF_PMP to actuate the pump. 

 

Here's what I saw:

 

 

So clearly I am getting PWM at the pump. All the other lines (power, ground) were fine at the pump end. The pump was NOT running when it saw this signal, so I suspected the pump was bad.

 

I ordered a replacement pump. I won't bore you with the story, but suffice it to say Ford doesn't have any, there were only two of them in the entire country, and it took me over two months to get it, at almost double the Ford MSRP. 

 

Today I put the pump on, and changed the transmission fluid for good measure. I went into ForScan and commanded the pump to run. Success! I heard the pump start up, and I could control its speed by adjusting the AUX_TLF_PMP value in ForScan. When the pump was running, the AUX_TFLPMP_FB (pump feedback) was showing 48.24%:

 

 

When the pump was not running, this AUX_TFLPMP_FB number went very high, around 88%.

 

Just as a test, I tried plugging the harness onto the old pump and commanded it to run. It did not run, and the AUXTFLPMP_FB value stayed at around 88% (the same as when the good pump was shut off). Plugging the harness back onto the good pump, it ran as expected.

 

So that's it, happy ending, the pump was bad and everything is fixed, right?

 

Not so fast! I cleared all the codes, and as a test, with the car in the air, ran it in EV Only mode, letting the wheels rotate in the air. It ran like this just fine for about five minutes or so, but suddenly the engine started up, and the car went back to "EV Unavailable" mode, and the check engine light illuminated. I pulled the codes, and sure enough, P2796 was back again.

 

The strange thing is - the new pump is WORKING. I can command it. I can see in the AUX_TFLPMP_FB feedback that it can see the pump running or not.

 

I tried resetting codes again and repeating the test, but it's still happening.

 

So now I'm a bit stuck. I'm not sure what to check next. I don't know what type of signal the pump is supposed to be sending back to the SOBDMC, so I can't really check it to see if it is correct or not. The SOBDMC is seeing SOMETHING, because the value being reported for AUX_TFLPMP_FB is changing when the pump is running compared to when the pump is not.

 

Anyone have any suggestions? Anyone fluent with ForScan with an Energi who could try commanding their pump to run and see if the numbers being reported for AUX_TFLPMP_FB are the same as I am seeing when the pump is both operating and not operating?

 

I'm not entirely sure what to look at next. the P2796 code is for when the pump is "not receiving a signal on its PWM wire from the SOBDMC" - but it clearly is, because the pump is running as expected. The only way the SOBDMC would know if it is running as expected or not is through the feedback line, and it's obviously seeing SOMETHING there, because that AUX_TFLPMP_FB number is changing - but I don't know if it is changing to correct values.

 

Open to suggestions here. Thanks for reading this novel!

 

The very rare and hard to find pump installed:

 

[GSMacLean]

Interesting...I had someone send me a more detailed Ford diagnostic document. In it, I found this...posting it here in case anyone ever searches for this information:

 

Transmission Auxiliary Oil Pump check malfunction thresholds:
P175A: TAOP circuit board temperature > 130 deg C for 3 sec.
P0B0D: TAOP speed is > 105% or < 95% of commanded speed for 3 sec
P0C27: TAOP current is < 0.5 Amps at 1000rpm to <1.2 Amps at 4000rpm. For 3 sec
P0C28: TAOP current is > 12.5 Amps for 3 sec
P0C29: TAOP current and speed meet conditions for P0B0D and either P0C27 or P0C28 for 3 sec.
P0C2A: Pump speed =0 when commanded non-zero for 3 sec, OR circuit board temp > 135 deg C OR Overcurrent
> 12.5 Amps for > 20 sec. OR Pump supplied voltage < 6.0 Volts or > 18.0 Volts for 325 ms.
P0C2C: Duty cycle of PWM signal measured by TAOP outside the 10 defined zones of operation > 3.0 sec.
P0C2D: Duty cycle of PWM signal measured from TAOP is < 9 % duty cycle for 3 seconds.
P0C2E: Duty cycle of PWM signal measured from TAOP is > 91 % duty cycle for 3 seconds.
P2796: PWM speed command signal on the separate control circuit < 80 Hz or > 120 Hz for 3 sec.

 

The last one, which I bolded, is the one that interests me. I'm going to have to put my scope back on there while the pump is running and see just what the frequency is. 

[GSMacLean]

I just realized that I never came back here to update this thread.

 

So the new pump was fine, and it did fix the problem. What was causing the issue to still show up was that I was testing the pump by sending it test values all the way from 0 to 100%, which the TCM never does. Doing so makes the TCM think something is wrong, and it throws the code again.

 

In normal operation, the pump feedback is either 48% or 88% and that seems correct - at least the TCM is happy with those numbers.

 

I've driven probably 500 miles since the new pump went on, and no more codes or problems, so I'm calling this fixed.

[13max]

On 4/4/2022 at 9:36 AM, GSMacLean said:

I just realized that I never came back here to update this thread.

 

So the new pump was fine, and it did fix the problem. What was causing the issue to still show up was that I was testing the pump by sending it test values all the way from 0 to 100%, which the TCM never does. Doing so makes the TCM think something is wrong, and it throws the code again.

 

In normal operation, the pump feedback is either 48% or 88% and that seems correct - at least the TCM is happy with those numbers.

 

I've driven probably 500 miles since the new pump went on, and no more codes or problems, so I'm calling this fixed.

Have been reading your problem, problem solving and resolution to your problem......Great stuff!

 

I am having issues now with my 2013 Cmax Energi and think it may be the same problem. Codes that I get are:

 

Code: P0C2A - Electric/Auxiliary Transmission Fluid Pump A Motor Stalled

Code: P0C2C - Electric Transmission Fluid Pump Control Module Feedback Signal Range/Performance

Will first try and clean the connections to the Aux Trans Pump.

 

Thanks,

Corby

[GSMacLean]

On 6/2/2022 at 8:45 AM, 13max said:

Have been reading your problem, problem solving and resolution to your problem......Great stuff!

 

I am having issues now with my 2013 Cmax Energi and think it may be the same problem. Codes that I get are:

 

Code: P0C2A - Electric/Auxiliary Transmission Fluid Pump A Motor Stalled

Code: P0C2C - Electric Transmission Fluid Pump Control Module Feedback Signal Range/Performance

Will first try and clean the connections to the Aux Trans Pump.

 

Thanks,

Corby

I've had quite a few people contact me and tell me that their pump had failed as well, so apparently it's going to become a more and more common failure item on our Energi's. Good luck finding a replacement!

Incidentally, make sure you do get the correct pump - there are lots of sites on the Internet that list the pump but show a different pump, used on other Ford vehicles. The part numbers are very similar. The pump on the CMax Energi is unique to it - it is the only one that looks like the one in my picture. The exact part number is LX6Z-7P086-B

 

Also beware of Internet sites that claim to have the pump in stock (which is almost all of them), but don't actually have the parts on hand, and simply order it from Ford after you place your order - and then a couple of weeks later realize that it is back-ordered from Ford with no ETA, and they cancel your order. Make SURE they actually have it in stock before placing your order, because virtually all of them operate this way.

[13max]

On 6/2/2022 at 8:01 AM, GSMacLean said:

I've had quite a few people contact me and tell me that their pump had failed as well, so apparently it's going to become a more and more common failure item on our Energi's. Good luck finding a replacement!

Incidentally, make sure you do get the correct pump - there are lots of sites on the Internet that list the pump but show a different pump, used on other Ford vehicles. The part numbers are very similar. The pump on the CMax Energi is unique to it - it is the only one that looks like the one in my picture. The exact part number is LX6Z-7P086-B

 

Also beware of Internet sites that claim to have the pump in stock (which is almost all of them), but don't actually have the parts on hand, and simply order it from Ford after you place your order - and then a couple of weeks later realize that it is back-ordered from Ford with no ETA, and they cancel your order. Make SURE they actually have it in stock before placing your order, because virtually all of them operate this way.

Thanks for the tip and I did confirm via Vin # but at this point not sure if I will get the part. 

 

My question is, is the car still drive able short distance? The only option is Auto (EV and EV later are disabled.

 

I will let you know if I am successful in getting the part.

 

Thanks,

Corby

[cr08]

On 6/2/2022 at 1:51 PM, 13max said:

Thanks for the tip and I did confirm via Vin # but at this point not sure if I will get the part. 

 

My question is, is the car still drive able short distance? The only option is Auto (EV and EV later are disabled.

 

I will let you know if I am successful in getting the part.

 

Thanks,

Corby

 

It -SHOULD- be drivable as long as it is operating in hybrid mode (I'm assuming it is with the ICE operating as such with it locked in Auto mode?). Basically, it is now operating the same as a Hybrid model C-Max as they do not have the auxiliary pump. There's a mechanical fluid pump spun by the ICE that is the same between both the Energi and Hybrid models.

[13max]

On 6/2/2022 at 10:51 AM, 13max said:

Thanks for the tip and I did confirm via Vin # but at this point not sure if I will get the part. 

 

My question is, is the car still drive able short distance? The only option is Auto (EV and EV later are disabled.

 

I will let you know if I am successful in getting the part.

 

Thanks,

Corby

Yep, Part availability is horrible.....May I ask where you purchased the 2 you managed to find?

 

Thanks,

Corby

[13max]

On 6/2/2022 at 1:49 PM, cr08 said:

 

It -SHOULD- be drivable as long as it is operating in hybrid mode (I'm assuming it is with the ICE operating as such with it locked in Auto mode?). Basically, it is now operating the same as a Hybrid model C-Max as they do not have the auxiliary pump. There's a mechanical fluid pump spun by the ICE that is the same between both the Energi and Hybrid models.

Yes, It is locked in Auto mode. it drives fine so I will just have to get use to the check engine light on...I will check the codes daily just in case something else pops up...Again thanks for your help, Very Much appreciated

[GSMacLean]

On 6/2/2022 at 5:30 PM, 13max said:

Yep, Part availability is horrible.....May I ask where you purchased the 2 you managed to find?

 

Thanks,

Corby

 

I had Ford search dealer stock nationwide. There were two dealers in the country that had one each, one of them was in Columbus, Ohio. I called that dealer up and bought it from them. They charged me almost double Ford's MSRP.

[cr08]

On 6/2/2022 at 8:05 PM, GSMacLean said:

 

I had Ford search dealer stock nationwide. There were two dealers in the country that had one each, one of them was in Columbus, Ohio. I called that dealer up and bought it from them. They charged me almost double Ford's MSRP.

 

Interesting. Do you happen to know which dealer in Columbus it was?

[13max]

Ok, so after I was unsuccessful in finding one I found out through multiple dealers that this part is shipped out of Sacramento. I asked my local ford Dealer and they have placed the order.....In the meantime I reviewed the code P0C28 - Electric/Aux Trans Fluid Pump A Motor Current High....I used a mirror to look at the contacts in side the male end of the connection attached to the pump and noticed green corrosion on on male end pin 1 and 4.....I cleaned these off, taking care not to bend any pins( and without taking  the pump off the vehicle, man was this awkward ), added a little Di electric grease and reassembled. I purposely did not clear the codes and left the Check engine light on I checked all 3 settings....E/V auto, EV and EV later were all available. I drove it around last night about 30 miles in total periodically checking the 3 settings (E/V auto, EV and EV later) and they were still available. After I stopped to get gas I started the car and the Check engine light was off as it must not have seen the same error code after so many miles. Drove it this morning and no check engine light and all 3 settings still available. Hoping the build up of corrosion was causing the intermittent connection and this has solved it for now.?

 

I would like to thank GSMacLean for offering your diagnostics from your experience, which greatly helped me with Part # and a starting point as to where to look for the issue.

 

I will update over the next couple days, weeks.

 

 

[WindyWags]

On 6/2/2022 at 10:01 AM, GSMacLean said:

Incidentally, make sure you do get the correct pump - there are lots of sites on the Internet that list the pump but show a different pump, used on other Ford vehicles. The part numbers are very similar. The pump on the CMax Energi is unique to it - it is the only one that looks like the one in my picture. The exact part number is LX6Z-7P086-B

You are stating neither of these are correct replacements?

FL3Z-7P086-B

DM5Z-7P086-C