Jeep Grand Cherokee WK. Manual — part 1457
U0424-IMPLAUSIBLE DATA RECEIVED FROM HVAC CONTROL MODULE
21 - 638
AUTOMATIC TRANSMISSION NAG1 - ELECTRICAL DIAGNOSTICS
WK
U0424-IMPLAUSIBLE DATA RECEIVED FROM HVAC CONTROL MODULE (CONTINUED)
For the Transmission circuit diagram (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - NAG1 - SCHE-
MATICS AND DIAGRAMS)
For a complete wiring diagram Refer to Section 8W
Theory of Operation
The messages sent on the CAN bus are distinguished by an identifier (ID). Each CAN ID is defined to contain a
certain number of bytes. The Transmission Control Module (TCM) verifies that it has received the proper number of
bytes for each ID.
•
When Monitored:
Continuously with the ignition on, one valid CAN ID received at least once, and no U0002-CAN Bus Off Per-
formance DTC present.
•
Set Condition:
When the TCM detects an incorrect CAN ID from the HVAC control module.
Possible Causes
CAN BUS DTC’S PRESENT
HVAC DTC’S PRESENT
TRANSMISSION CONTROL MODULE
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 21 - TRANSMIS-
SION/TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)
Diagnostic Test
1.
CHECK FOR FCM CAN BUS DTCS
With the scan tool, read FCM DTCs.
Are there any FCM CAN BUS DTC’s present?
Yes
>> Refer to 8-ELECTRICAL - ELECTRONIC CONTROL MODULES - ELECTRICAL DIAGNOSTICS cate-
gory and perform the appropriate symptom.
No
>> Go To 2
2.
CHECK IF HVAC DTC’S ARE PRESENT
With the scan tool, read HVAC DTCs.
Are there any HVAC DTC’s present?
Yes
>> Refer to Section 24 - HVAC - ELECTRICAL DIAGNOSTICS category and perform the appropriate symp-
tom.
Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1.
No
>> Using the schematics as a guide, check the Transmission Control Module (TCM) pins, terminals, and
connectors 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 - ELECTRI-
CAL/ELECTRONIC CONTROL MODULES/TRANSMISSION CONTROL MODULE for the appropriate
service procedure.
Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1.
WK
AUTOMATIC TRANSMISSION NAG1 - ELECTRICAL DIAGNOSTICS
21 - 639
U0431-IMPLAUSIBLE DATA FROM FCM
21 - 640
AUTOMATIC TRANSMISSION NAG1 - ELECTRICAL DIAGNOSTICS
WK
U0431-IMPLAUSIBLE DATA FROM FCM (CONTINUED)
For the Transmission circuit diagram (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - NAG1 - SCHE-
MATICS AND DIAGRAMS)
For a complete wiring diagram Refer to Section 8W
Theory of Operation
The messages sent on the CAN bus are distinguished by an identifier (ID). Each CAN ID is defined to contain a
certain number of bytes. The Transmission Control Module (TCM) verifies that it has received the proper number of
bytes for each ID.
•
When Monitored:
Continuously with the ignition on, one valid CAN ID received at least once, and no U0002-CAN Bus Off Per-
formance DTC present.
•
Set Condition:
When the TCM detects an incorrect CAN ID from the FCM.
Possible Causes
FCM CAN BUS DTC’S PRESENT
TRANSMISSION CONTROL MODULE
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 21 - TRANSMIS-
SION/TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)
Diagnostic Test
1.
CHECK FOR FCM CAN BUS DTCS
With the scan tool, read FCM DTCs.
Are there any FCM CAN BUS DTC’s present?
Yes
>> Refer to 8-ELECTRICAL - ELECTRONIC CONTROL MODULES - ELECTRICAL DIAGNOSTICS cate-
gory and perform the appropriate symptom.
No
>> Using the schematics as a guide, check the Transmission Control Module (TCM) pins, terminals, and
connectors 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 - ELECTRI-
CAL/ELECTRONIC CONTROL MODULES/TRANSMISSION CONTROL MODULE for the appropriate
service procedure.
Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1.
WK
AUTOMATIC TRANSMISSION NAG1 - ELECTRICAL DIAGNOSTICS
21 - 641
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