DTC P1900

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DTC P1900: EOP-RELAY High Input

General Description

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

The auxiliary transmission fluid pump provides hydraulic pressure to control the CVT instead of the transmission fluid pump that would stop at auto idle stop. The auxiliary transmission fluid pump system consists of the three-phase brushless motor (to drive the fluid pump), the driver, and the auxiliary transmission fluid pump relay. The power source that drives the auxiliary transmission fluid pump is provided from the DC-DC converter via the auxiliary transmission fluid pump relay that is controlled by the transmission control module (TCM). The TCM and the auxiliary transmission fluid pump are connected by two communication lines (EOPSIG, EOPSTS). The TCM sends a start command (90 % duty ratio) or a stop command (5 % duty ratio) to the auxiliary transmission fluid pump by pulse width modulation (PWM) (100 Hz). In accordance to the start (or stop) command from the TCM, the auxiliary transmission fluid pump starts (or stops) the auxiliary transmission fluid pump motor. The auxiliary transmission fluid pump sends its motor speed data to the TCM using the pulse. The auxiliary transmission fluid pump motor rotates at a motor speed of 1, 000 - 5, 000 rpm which varies depending on transmission fluid temperature. The motor speed could be obtained from the product of 30 times pulse frequency (Hz) (ex. 3, 000 rpm when 100 Hz). Just after the vehicle is turned to the ON mode, the auxiliary transmission fluid pump relay is OFF and the output line EOPSTS is HIGH. And then, the auxiliary transmission fluid pump relay turns to ON and the output line EOPSTS turns to LOW. If the auxiliary transmission fluid pump motor speed is at normal speed range for certain period of time when the auxiliary transmission fluid pump relay is ON (EOPSTS: LOW) just after the vehicle is turned to the ON mode, the TCM detects a malfunction and stores a DTC.

Monitor Execution, Sequence, Duration, DTC Type

Execution	Continuous
Sequence	None
Duration	5 seconds or more
DTC Type	Two drive cycles, MIL off, Shift position indicator blinks

Enable Conditions

Condition	Minimum	Maximum
12 volt battery voltage [Battery Voltage]	10 V	-
State of the engine	During auto idle stop operation

[ ]: HDS Parameter

Malfunction Threshold

The auxiliary transmission fluid pump motor speed is 301 - 8, 737 rpm for at least 5 seconds when the auxiliary transmission fluid pump relay is ON (EOPSTS: LOW) just after the vehicle is turned to the ON mode.

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.

TCM EOPRLY line short to ground
Auxiliary transmission fluid pump EOPVB line short to power
Auxiliary transmission fluid pump relay stuck on
TCM internal failure

Confirmation Procedure

Operating Condition

Turn the vehicle to the ON mode, and wait for at least 5 seconds.
Start the engine and wait for at least 5 seconds in auto idle stop condition.

With the HDS

Turn the vehicle to the ON mode, and wait for at least 5 seconds.
Select the Auxiliary Transmission Fluid Pump Test in the Miscellaneous Test Menu, and drive the auxiliary transmission fluid pump for at least 5 seconds with the HDS.

Diagnosis Details

Conditions for setting the DTC

When a malfunction is detected during the first drive cycle, a Pending DTC is stored in the TCM memory. If the malfunction returns in the next (second) drive cycle, the shift position indicator blinks and a Confirmed DTC and the freeze data are stored. The MIL does not come on.

Conditions for clearing the DTC

The shift position indicator comes off by turning the vehicle to the OFF (LOCK) mode. The Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool Clear command.