DTC U0122 (PGM-FI System (1.5 L Engine))

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DTC U0122: F-CAN Malfunction (Powertrain Control Module (PCM)-VSA Modulator-Control Unit)

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 powertrain control module (PCM) detects a malfunction and stores a DTC.

Monitor Execution, Sequence, Duration, DTC Type

Execution	Continuous
Sequence	None
Duration	1.5 seconds or more

*1:'18-21CVT model,'18-19M/T model

*2:'20-21M/T model

DTC Type* 1	One drive cycle, MIL off
DTC Type* 2	Two drive cycles, MIL on

*1:'18-21CVT model,'18-19M/T model

*2:'20-21M/T model

Enable Conditions

Condition	Minimum	Maximum
Elapsed time after the vehicle condition is turned to the ON mode	3 seconds	-
12 volt battery voltage [BATTERY]	10.0 V	-

[ ]: HDS Parameter

Malfunction Threshold

One of these conditions is met:

The PCM does not receive any signals via the 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
F-CAN circuit F-CAN B L line open
F-CAN circuit F-CAN B H line short to ground
F-CAN circuit F-CAN B L line short to ground
VSA modulator-control unit failure (include fuse blown)
PCM internal circuit failure

Diagnosis Details* 1

Conditions for setting the DTC

When a malfunction is detected, a Pending DTC, a Confirmed DTC, and the freeze data are stored in the PCM memory. The MIL does not come on.

Conditions for clearing the DTC

The Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool clear command or by disconnecting the 12 volt battery.

Diagnosis Details* 2

Conditions for setting the DTC

When a malfunction is detected during the first drive cycle, a Pending DTC is stored in the PCM memory. If the malfunction returns in the next (second) drive cycle, the MIL comes on and a Confirmed DTC and the freeze data are stored.

Conditions for clearing the DTC

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 or by disconnecting the 12 volt battery.