SPN 639 - FMI 9 (Fault Code 427)

SPN639 FMI9 (J1939 Datalink - Abnormal Update Rate)
Fault Code 427

ISB, ISC, and ISL with CM2150 - SAE J1939 Data Link Circuit

Fault Code: 427
PID(P), SID(S): S231
SPN: 639
FMI: 9/9
Lamp: None

REASON: J1939 Datalink - Abnormal Update Rate. Communication between the electronic control module (ECM) and another device on the SAE J1939 data link has been lost.

EFFECT: Engine speed will ramp down and remain at idle.

Circuit Description:
Devices such as ABS controllers, autoshift transmissions, ASR systems, electronic displays, electronic information systems, electronic service tools, and vehicle electronic control unit(s) (VECUs) can communicate with the ECM over the SAE J1939 data link. Messages sent from the devices are received by the ECM and used for controlling the engine. The ECM also transmits information to these devices over the SAE J1939 data link.

Component Location:
The ECM is located on the intake side of the engine, near the front. The SAE J1939 data link wiring and the SAE J1939 devices vary by OEM options.

Conditions for Running the Diagnostics:
This diagnostic runs continuously when the keyswitch is in the ON position.

Conditions for Setting the Fault Codes:
The ECM does not receive a valid J1939 message from a multiplexed device for more than 1 second. The ECM detects an open or short circuit condition in the J1939 datalink harness.

Action Taken When the Fault Code is Active:
• The ECM will log the fault code immediately when the diagnostic runs and fails.
• The ECM will use a default state as an input for the multiplexed device.

Conditions for Clearing the Fault Code:
The ECM will set the fault code inactive immediately after the diagnostic runs and passes.

Shop Talk:
Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe® Online for applicable fixes to the calibration stored in the ECM. If necessary, recalibrate the ECM.

This fault occurs whenever the ECM has been receiving SAE J1939 datalink commands from an external OEM device and is no longer receiving the datalink commands. Possible causes of this fault include:
• Electrical problems with the SAE J1939 data link wiring such as grounded, shorted, or open circuits
• The ECM (or another SAE J1939 device) tying up communications by sending too many consecutive messages
• The external OEM controlling device has failed or can no longer transmit on the datalink.

Read More:
SPN 97 - FMI 3 (Fault Code 428)
SPN 639 - FMI 9 (Fault Code 285)


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