Content .. 1902 1903 1904 1905 ..
Chrysler 300/300 Touring/300C, Dodge Magnum. Manual - part 1904
Theory of Operation
The Transmission Control Module (TCM) receives information from the Engine, Anti-lock Brake System, and the
Electronic Gear Shift control modules over the CAN C bus. The CAN C bus is a high speed communication bus that
allows real time control capability between various controllers. Most messages are sent every 20 mSec, this means
critical information can be shared between multiple controllers almost instantaneously. The CAN C bus is a two wire
bus with a CAN (+) and a CAN (-) circuit. To reduce the potential of radio and other electrical noise interference, the
CAN Bus circuit wiring is manufactured using a twisted pair configuration within the electrical wiring harness.
•
When Monitored:
Continuously with the ignition on.
•
Set Condition:
The DTC will set if a valid CAN ID was not received in the required time from the ABS.
Possible Causes
TRANSMISSION CONTROL MODULE
Always perform the NAG1 Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 21 -
TRANSMISSION/TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)
Diagnostic Test
1.
CHECK THE FCM FOR CAN C BUS COMMUNICATION DTCS
With the scan tool, check for FCM DTCs.
Does the FCM report the DTC U0001-CAN C BUS DTC or U0121-LOST COMMUNICATION WITH ANTI-
LOCK BRAKE MODULE?
Yes
>> Refer to 8-ELECTRICAL - ELECTRONIC CONTROL MODULES - ELECTRICAL DIAGNOSTICS cate-
gory and perform the appropriate symptom. Perform the diagnostic procedure for U0001-CAN C BUS
first if it is present.
Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21 - TRANSMISSION/
TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)
No
>> Go To 2
2.
CHECK IF THE DTC IS CURRENT
NOTE: When the Transmission Control Module (TCM) detects and stores a DTC, the TCM also stores the
vehicles operating conditions under which the DTC originally set. This information is located in the scan
tool under Environmental Data. Before erasing any stored DTCs, record any available data to assist in dupli-
cating the conditions in which the DTC originally set.
Ignition on, engine not running.
With the scan tool, erase Transmission DTC’s.
Using the Environmental Data recorded earlier, try to duplicate the conditions in which the DTC originally set. It may
be necessary to test drive the vehicle.
With the scan tool, read Transmission DTC’s.
Did the DTC U0121-LOST COMMUNICATION WITH ANTILOCK BRAKE MODULE reset?
Yes
>> Using the schematics as a guide, check the Transmission Control Module (TCM) terminals for corrosion,
damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems
are found, replace the TCM per the Service Information. (Refer to 8 - ELECTRICAL/ELECTRONIC
CONTROL MODULES/TRANSMISSION CONTROL MODULE - DESCRIPTION)
Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21 - TRANSMISSION/
TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)
No
>> Go To 3
21 - 150
AUTOMATIC TRANSMISSION NAG1 - ELECTRICAL DIAGNOSTICS
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