All the other lines (power, ground) were fine at the pump end. I put my scope on the PWM control signal, and using ForScan, commanded the AUX_TLF_PMP to actuate the pump. 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. So I pulled the connector at the pump end. Why Ford skips that possibility in the service manual, I have no idea. I'm thinking perhaps the pump is at fault. 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 took the car out for a test drive, and within a mile or so, it threw the same code again.Īccording to Ford, the next "diagnostic step" is to replace the SOBDMC. I cleaned all the contacts and reseated everything. 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. 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. The pump sends back a signal of some kind to the SOBDMC to let it know that it is working. The SOBDMC controls the pump's speed by sending a PWM (pulse-width modulated) signal. 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. 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. So the Energi has an auxiliary transmission fluid pump bolted to the outside of the transmission. This DTC sets when the E-pump is not receiving a signal on it's PWM input signal from the SOBDMC / TCM . When I got home, I pulled the codes, and got a P2796:00 - here's what the service manual has to say about this:Įlectric Transmission Fluid Pump Control Circuit Shortly afterwards, I got a check engine light. Both EV modes were disabled (greyed out with an "X" through them) and the only option it gave me was "EV Later". So back in December while out driving, my 2013 Energi, despite having almost a full battery charge, abruptly started running on its engine.
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