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

General Description
Without CAN gateway

With CAN gateway

The controller area network (CAN) transmits/receives pulsing signals to/from the control modules simultaneously by using two signal lines (F-CAN_H and F-CAN_L). When the powertrain control module (PCM) does not receive the signals from the VSA modulator-control unit via the CAN lines for a certain period of time or receives incorrect message frames, the PCM detects a malfunction and stores a DTC.

Monitor Execution, Sequence, Duration, DTC Type
Execution
Continuous
Sequence
None
Duration
0.5 second or more
DTC Type
Two drive cycles, MIL on

Enable Conditions
Condition
Minimum
Maximum
Elapsed time since the 12 volt battery voltage reaches to a specified value
5.0 seconds
–
12 volt battery voltage [Battery]
10.04 V
–
Vehicle
ON mode
[ ]: HDS Parameter

Malfunction Threshold
Any of the conditions is met for at least 0.5 second:
Checksum error
The value of checksum for the received message is different from the calculated checksum.
Message counter error
?
The two consecutive values of the message counter are equal at least once.
?
The difference between two consecutive values of the message counter is greater than 255.
Timeout error
The CAN message frame is not received.

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_H*1, F-CAN A_H*2 line open
F-CAN circuit F-CAN_L*1, F-CAN A_L*2 line open
F-CAN circuit F-CAN_H*1, F-CAN A_H*2 line short to ground
F-CAN circuit F-CAN_L*1, F-CAN A_L*2 line short to ground
F-CAN circuit F-CAN B_H*2 line open
F-CAN circuit F-CAN B_L*2 line open
F-CAN circuit F-CAN B_H*2 line short to ground
F-CAN circuit F-CAN B_L*2 line short to ground
VSA modulator-control unit failure (include fuse fall-outs)
PCM internal circuit failure

*1: Without CAN gateway
*2: With CAN gateway

Diagnosis Details
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.