SPN 602 FMI 13 – J1939 Cruise Control Accelerate Switch Signal from Source #1, #2, or #3 is missing or not available Fault Code (Symptoms, Causes & Fix)
The SPN 602 FMI 13 fault code indicates a missing or unavailable signal from the J1939 Cruise Control Accelerate Switch, sourced from #1, #2, or #3. This diesel engine fault code suggests that the Engine Control Module (ECM) is not receiving the expected signal from the cruise control system, which can affect the vehicle's ability to maintain or adjust speed using cruise control.
What SPN 602 FMI 13 Means
When the SPN 602 FMI 13 fault code is active, it signifies that the ECM is not detecting the necessary signal from the cruise control accelerate switch via the J1939 data link. This can occur due to issues with the switch itself, the wiring, or the data link communication. The ECM interprets this as a failure to receive the expected input, which can disrupt cruise control functionality.
Common Causes of This Fault Code
- Faulty cruise control switch
- Damaged or corroded wiring harness
- Defective J1939 data link
- Faulty ECM/PCM
- Loose or corroded connectors
Symptoms Drivers May Notice
When this fault code is active, drivers may notice that the cruise control system is unresponsive or fails to maintain the set speed. The cruise control may not engage at all, or it may disengage unexpectedly. Additionally, there might be a warning light on the dashboard indicating a cruise control issue.
How Technicians Diagnose This Fault
Technicians begin by performing a visual inspection of the cruise control switch for any physical damage or wear. Next, they check the wiring harness for any signs of damage, corrosion, or loose connections. Using a multimeter, they perform a continuity test on the wiring from the cruise control switch to the ECM. They also verify the integrity of the J1939 data link communication using diagnostic software. Finally, they test the ECM/PCM to ensure it responds correctly to cruise control inputs.
Common Misdiagnosis
One common mistake is replacing the cruise control switch without first verifying the integrity of the wiring. Another is assuming ECM/PCM failure without checking for issues in the data link communication. Technicians may also overlook corrosion or loose connections in the connectors, leading to misdiagnosis.
Can You Keep Driving?
While the vehicle can generally continue to operate with this fault code active, the cruise control system will likely be non-functional. This may not pose an immediate safety risk, but it can affect driving comfort and efficiency on long trips. It's advisable to address the issue to restore full functionality of the cruise control system.
Mechanic's Diagnostic Tip
Always ensure that the battery voltage and overall system voltage are within specifications before diving into more complex diagnostics. Low voltage can lead to erroneous fault codes and misdiagnosis. This simple check can save time and prevent unnecessary part replacements.
Frequently Asked Questions
Q: Can a faulty cruise control switch cause SPN 602 FMI 13?
A: Yes, a faulty switch is one of the common causes of this fault code.
Q: Is it necessary to replace the ECM if this code is active?
A: Not necessarily. Always verify the integrity of the wiring and data link before considering ECM replacement.
Q: How can I prevent this fault from occurring?
A: Regular maintenance checks on the wiring harness and connectors can help prevent issues leading to this fault code.
