Detroit DD13 EPA07 (2007-09) Fault Code: SPN 904 FMI 13 (CPC) – Front Axle Speed Signal is Missing

Detroit DD13 EPA07 (2007–09) – SPN 904 FMI 13 (CPC): Front Axle Speed Signal is Missing

Fault Code Overview

Fault Code Description

SPN 904 FMI 13 is set by the Common Powertrain Controller (CPC) when the front axle speed signal expected over the J1939 datalink is not received. The CPC uses this signal — typically broadcast by the ABS module — for engine brake coordination and vehicle speed management. A missing signal indicates a complete J1939 communication failure from the ABS module, a CPC programming mismatch, or a datalink conflict caused by another module on the network.

Note: Front axle speed signal is missing.

Note: If fault codes 168-0, 168-14, or 168-18 are active, repair those first before diagnosing this code.

Probable Causes

1. CPC has improper programming (incorrect configuration for the vehicle’s ABS or speed sensor system).
2. Another module on the vehicle (ABS, Transmission, Cab controller, etc.) is causing J1939 datalink conflicts or preventing the front axle speed message from being transmitted.

Symptoms

• Amber warning lamp illuminated on the dash
• SPN 904 FMI 13 logged in the CPC fault memory
• Front axle speed reading absent or zero in DDDL live data
• Engine brake or vehicle speed-related functions may be affected

Diagnostic Steps

1. Connect diagnostic software (Detroit Diesel DiagnosticLink / DDDL) and confirm the active fault code SPN 904 FMI 13 in the CPC. Note all other active fault codes.
2. Check for voltage-related codes first — if fault codes 168-0, 168-14, or 168-18 (battery voltage faults) are active, diagnose and repair those before proceeding. Voltage instability can cause multiple J1939 communication faults.
3. Verify CPC programming — using DDDL or DiagnosticLink, confirm the CPC is programmed correctly for the vehicle’s ABS system and front axle speed sensor configuration. If the CPC is configured to expect a front axle speed message that the installed ABS system does not transmit, reprogram with the correct configuration.
4. Check the J1939 datalink — inspect the J1939 backbone wiring and terminating resistors. Measure resistance across the J1939 datalink (should read approximately 60 ohms with both terminators in place). An open or shorted datalink will prevent the ABS module from communicating with the CPC.
5. Inspect ABS module communication — connect to the ABS module with the appropriate diagnostic tool and verify it is active on the J1939 network and transmitting the front axle speed message. Check for ABS module fault codes related to wheel speed sensors or J1939 communication errors.
6. Check for datalink conflicts — if multiple modules (transmission, cab controller, etc.) are present, check for any module that may be disrupting J1939 communication. Disconnect suspect modules one at a time while monitoring for fault resolution.
7. Inspect J1939 wiring and connectors — check for damaged, corroded, or loose connectors at the CPC, ABS module, and J1939 datalink junction points. Repair as needed.
8. Clear the fault code and perform a key cycle. Monitor the front axle speed signal in DDDL live data to confirm it is present and stable. Verify the fault does not return.

Related Fault Codes

• SPN 904 FMI 19 – Front Axle Speed Signal is Erratic
• SPN 904 FMI 9 – EBC2 Message from ABS is Missing
• SPN 168 FMI 0 – Battery Voltage High
• SPN 168 FMI 14 – Battery Voltage Special Instruction
• SPN 168 FMI 18 – Battery Voltage Low

Recommended Tools

• Detroit Diesel DiagnosticLink (DDDL) software
• ABS diagnostic tool (Bendix ACom, Meritor TOOLBOX, or equivalent)
• Digital multimeter
• Wiring diagram for Detroit DD13 EPA07
• RP1210-compliant diagnostic adapter (Nexiq USB Link, Noregon DLA+, etc.)

Always refer to the official Detroit Diesel service documentation and wiring diagrams for your specific vehicle configuration before performing repairs.