DTC U0122 (CVT)

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DTC U0122: Lost Communication With Vehicle Dynamics Control Module

General Description

Without ACC

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

With ACC

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

The controller area network (CAN) transmits/receives pulsing signals to/from the control modules simultaneously by using two signal lines (H line and L line). When the information is not sent from the VSA modulator-control unit via the F-CAN lines and this condition continues for a specified time or when the information sent from the VSA modulator-control unit is abnormal and this condition continues for a specified cycle, the transmission control module (TCM) detects a malfunction and stores a DTC.

Monitor Execution, Sequence, Duration, DTC Type

Execution	Continuous
Sequence	None
Duration	1.5 seconds or more
DTC Type	One drive cycle, MIL off, Shift position indicator blinks

Enable Conditions

Condition	Minimum	Maximum
12 volt battery voltage [Battery Voltage]	10.0 V	-

[ ]: HDS Parameter

Malfunction Threshold

One of these conditions is met:

The TCM does not receive any signals from the VSA modulator-control unit via F-CAN lines for at least 1.5 seconds.
The information sent from the VSA modulator-control unit is abnormal at least 20 times.

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.

F-CAN circuit F-CAN A_H line open
F-CAN circuit F-CAN A_L line open
F-CAN circuit F-CAN A_H line short to ground
F-CAN circuit F-CAN A_L line short to ground
F-CAN circuit F-CAN B_H line open* 1
F-CAN circuit F-CAN B_L line open* 1
F-CAN circuit F-CAN B_H line short to ground* 1
F-CAN circuit F-CAN B_L line short to ground* 1
VSA modulator-control unit failure (include fuse blown)
TCM internal circuit failure

*1: With ACC

Confirmation Procedure

Operating Condition

Turn the vehicle to the ON mode.
Turn the vehicle to the OFF (LOCK) mode.

With the HDS

None.

Diagnosis Details

Conditions for setting the DTC

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