U0287: Lost Communication With Transmission Fluid Pump Module A

What it means

The vehicle bus reports loss of communication with transmission fluid pump module A. Auxiliary ATF pumping during start/stop or hybrid coast cannot be commanded, which may delay shifts or impair cooling.

At a glance

• Usually lights the warning light of the system that lost communication
• The engine or gearbox may go into limp mode

How it works

Transmission fluid pump module A controls an auxiliary pump that can circulate transmission fluid when the main pump is not providing flow, such as during some stop/start or hybrid operating conditions. The transmission controller expects network messages from module A; this code sets when those messages are lost, preventing the pump from being commanded normally.

Common causes

Most likely first.

1. Bus wiring open or shorted
2. Module without power or ground
3. Module failed

Symptoms

• Multiple warning lights may illuminate
• Affected modules may go into limp mode or shut down
• Specific functions inoperative depending on module
• Diagnostic tools may show communication faults

How to diagnose it

1. Scan the transmission and other modules for related communication, voltage, and transmission faults, and save freeze-frame data before clearing anything.
2. Check whether transmission fluid pump module A responds to the scan tool and whether pump status or command data is available.
3. Inspect module A's connector and harness for fluid intrusion, corrosion, chafing, or impact damage.
4. Test module A's power and ground under the manufacturer's specified conditions, since a supply fault can interrupt communication.
5. With the vehicle powered down according to the manufacturer's procedure, test the network branch to module A for opens, shorts, or poor connections.
6. If the module has correct supplies and network wiring but remains offline, follow the manufacturer's diagnosis before replacing it; do not command the pump unless the procedure allows it.

Common fixes

• Secure a loose transmission fluid pump module A connector.
• Repair damaged or corroded wiring or network connections at module A.
• Restore module A's power or ground supply.
• Replace module A if its circuits test correctly but it does not communicate.

Can I keep driving?

Avoid continued driving if shifts are delayed, harsh, or accompanied by a transmission warning; loss of auxiliary pumping can affect fluid circulation and cooling in some operating conditions. If the vehicle enters limp mode or shifting changes, stop in a safe place and arrange diagnosis before driving farther.