Auxiliary Transmission Fluid Pump (ATFP, Also Known As EPUMP)
For Stop / Start purposes 10R80 comes equipped with an Auxiliary Transmission Fluid Pump (ATFP, also known as ePump), an electronic pump that can be turned on before an engine stop event, allowing the transmission to stay engaged during the stop event. This allows quick response on the engine restart because the transmission is already in gear. The ATFP does not have sufficient flow to apply clutches, but can keep clutches on when the engine stops and the main hydraulic pump stops providing pressure.
- ATFPC - TCM or PCM commanded pump speed
- ATFPD - Diagnostics status for the ATFP
The AFTP is a smart actuator that communicates with the TCM (or PCM) via PWM hardwires:
The TCM or PCM performs circuit diagnostics on the diagnostics hardwire (ATFPD):
| Fault | DTC |
| Frequency out of range (expected frequency is 150 +/- 20 Hz) | P0C2C |
| Duty cycle out of range low (< 10%) | P0C2D |
| Duty cycle out of range high (> 90%) | P0C2E |
The remainder of the diagnostics are performed by the AFTP, the TCM or PCM simply stores the DTC's because the device is not on CAN so it is unable to store its own DTC's or communicate with a service tool.
ATFP detected faults are mapped to DTCs as follows:
| Fault | DTC |
| ATFP reporting incorrect speed | P0B0D |
| ATFP reporting under current | P0C27 |
| ATFP reporting over current | P0C28 |
| ATFP reporting current and speed both out of range | P0C29 |
| ATFP reporting pump stalled (may have lost prime) | P0C2A |
| ATFP reports an over temperature condition | P175A |
| ATFP reports it is not receiving the command PW M signal (ATFPC) | P2796 |
If an ATFP fault is present the stop / start system will be taken out of operation with the engine running (no more stop events while the fault is present). Failures of the diagnostics PWM can recover during a drive cycle, but most of the faults detected by the AFTP can only be detected when the pump is turned on - those faults will require a key cycle to recover.