DTC U12A4

DTC U12A4: F-CAN Malfunction (Powertrain Control Module (PCM)-Electric Coolant Heater)

General Description

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 powertrain control module (PCM) does not receive the signals from the electric coolant heater via the F-CAN lines for a set time, the PCM 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

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

The PCM does not receive any signals via the F-CAN lines for at least 1.5 seconds.
The information sent from the electric coolant heater 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
Electric coolant heater failure (include fuse fall-outs)
PCM internal circuit failure

Diagnosis Details

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.