The controller area network (CAN) is a high speed system for sharing data. The
circuit consists of a two wire twisted pair connecting the engine control module (ECM)
to the transmission control module (TCM), and a second twisted pair connecting the
body control module (BCM) to the ECM.
The CAN circuits are monitored continuously by the modules on the circuit. The
only requirement is that the modules are in an ON power mode.
The MIL light is cleared, turned OFF, and the DTC cleared by a different strategy
for each module.
| • | If the fault is not detected 3 consecutive drive cycles, the current
DTC is cleared and the MIL is turned OFF. |
| • | The history DTC is cleared if the malfunction does not reoccur for 40 consecutive
drive cycles. |
| • | The history DTC is cleared if there is a battery disconnect. |
| • | If the fault is not detected 3 consecutive drive cycles, the current
DTC is cleared and the MIL is turned OFF. |
| • | The history DTC is cleared if the malfunction does not reoccur for 40
consecutive drive cycles. |
| • | The history DTC is cleared if there is a battery disconnect. |
The module setting the DTC has attempted to establish communications on the
CAN circuits more than 7 times. After the seventh attempt, the module sets
this DTC.
Besides storing the DTC as both current and history, the modules on the CAN
network each take separate actions as listed:
| • | Turn ON the malfunction indicator lamp (MIL) during the second consecutive
drive cycle with the error detected. |
| • | Record the operating conditions at the time of turning ON the MIL and
store the data as Freeze Frame information. |
| • | Turn ON the MIL during the second consecutive drive cycle with the error
detected. |
| • | Record the operating conditions at the time of turning ON the MIL and
store the data as Freeze Frame information. |
DTC U2104
