DTC P2685, P2686

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DTC P2685: Actuator Supply Voltage C Circuit Low DTC P2686: Actuator Supply Voltage C Circuit High

General Description

Courtesy of HONDA, U.S.A., INC.

The actuator supply voltage is for the power to drive the CPU in the transmission control module (TCM). From the perspective of a fail-safe, three systems (VB1, VB2, and VB3) of the power supply lines are secured. They also have a role to supply power to the clutch pressure control solenoid valves and the shift solenoid valves. The TCM monitors whether the VB3 voltage is in a normal range by the CPU. If the VB3 voltage is a specified value for a set time, the TCM detects a malfunction and stores a DTC.

Monitor Execution, Sequence, Duration, DTC Type

Execution	Continuous
Sequence	None
Duration*	500 milliseconds or more
Duration**	600 milliseconds or more
DTC Type	One drive cycle, MIL on, Shift position indicator blinks

*: DTC P2685

**: DTC P2686

Enable Conditions

Condition	Minimum	Maximum
Elapsed time after the vehicle condition is turned to the OFF (LOCK) mode**	30 seconds	-
12 volt battery voltage [Battery Voltage]	10 V	-
Vehicle	ON mode
Other*	Fail-safe switch is on

[ ]: HDS Parameter

Malfunction Threshold

DTC: P2685

The VB3 voltage is 5.6 V or less for at least 500 milliseconds

DTC: P2686

The VB3 voltage is 7.2 V or more for at least 600 milliseconds.

Possible Cause

NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.

DTC: P2685

TCM VB3 line short to ground
TCM VB3 line open (include fuse blown)

DTC: P2686

Fail-safe switch stuck on

Common

TCM internal circuit failure

Confirmation Procedure

Operating Condition

DTC: P2685

Turn the vehicle to the ON mode, and wait for at least 5 seconds.

DTC: P2686

Turn the vehicle to the ON mode.
Turn the vehicle to the OFF (LOCK) mode, and wait for at least 30 seconds.
Turn the vehicle to the ON mode, and wait for several seconds.

With the HDS

None.

Diagnosis Details

Conditions for setting the DTC

When a malfunction is detected, the MIL comes on, the shift position indicator blinks, and a Pending DTC, a Confirmed DTC, and the freeze data are stored in the TCM memory.

Conditions for clearing the DTC

The shift position indicator comes off by turning the vehicle to the OFF (LOCK) mode. The MIL is cleared if the malfunction does not return in three consecutive trips in which the diagnostic runs. The MIL, the Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool Clear command.