How To: Troubleshooting Intermittent Electrical Faults in Emissions Systems

How To: Troubleshooting Intermittent Electrical Faults in Emissions Systems

🔧 How to Troubleshoot Intermittent Electrical Faults in Emissions Systems

Intermittent electrical faults are some of the most frustrating problems to deal with, especially when working on complex emissions systems in heavy equipment and trucks. These faults come and go, making it tough to track down the root cause. But with the right approach, you can systematically identify and fix them — saving time, money, and a lot of headaches.

Here’s a step-by-step guide to help you diagnose intermittent electrical issues like a pro:

✅ Understand the System First

Before grabbing your multimeter, take time to:

  • 📚 Understand how the emissions system works — know which components talk to each other.
  • 🔄 Review wiring diagrams and fault codes.
  • ❓ List possible components that could cause the issue (ex. sensors, actuators, wiring, ECM).
  • 🎯 Prioritize your list by likelihood and ease of access. Always start with the most likely and easiest checks first!

Tip: If you haven't fixed the issue after the easy checks, you'll have already ruled out a good chunk of possibilities — and saved time!

🔴 Active vs. Inactive Fault Codes

One key to troubleshooting intermittent faults is knowing if the fault is:

  • Active (Current) Faults 🔥 — These are happening right now. These are goldmines for testing, since the problem is present!
  • Inactive (History) Faults 🕑 — These happened in the past. They tell you something went wrong, but it may not be happening now.

Active faults are the best chance to catch a problem "in the act."

🧰 Step-by-Step Troubleshooting Approach

1. Start with Visual Inspections 👀

  • Check all connectors and wiring related to the fault code.
  • Look for loose, corroded, or dirty connections.
  • Check pigtails and connectors — these are common failure points.

Fun fact: Many wiring issues happen right under a zip tie or close to connectors where wires are bent or stressed.

2. Wiggle Test the Harness 🪢

  • Gently wiggle the harness at various points — especially near fasteners, clamps, and tight bends.
  • Watch for faults to come and go as you move the wiring.
  • Pay special attention to:
    • Near the pigtail/connector ends.
    • Under or near zip ties.
    • Any place where the harness is rubbing or tightly bent.

3. Look for Chafed, Worn, or Cut Wires ✂️

  • Inspect for rubbing damage where the harness contacts metal or other parts.
  • Check spots where the harness is secured to the frame — these are notorious wear points.
  • Don't forget to peel back loom or tape if you suspect hidden damage!

4. Tap Test Components 🔨

  • Some sensors, modules, and connectors will fault when tapped if there's a poor internal connection.
  • Lightly tap the component while monitoring fault codes or live data.
  • If a tap triggers a fault — you’ve found a suspect part!

5. Understand the Fault's Behavior 💡

  • Is the fault temperature-related (e.g., only when hot or cold)?
  • Does it happen during vibration (like driving on rough roads)?
  • Does it happen at startup or shutdown?

Knowing when the fault happens gives you clues on what to check first.

⚙️ Plan Your Diagnosis Efficiently

  • 🧠 Think before acting — plan your steps based on the system's operation.
  • ✅ Test the easy and likely things first.
  • 🛠️ Move to harder-to-access parts last, but keep them on your radar.
  • 🔁 If you’ve reached the end of your checklist and still haven’t found the problem, you’ve now ruled out a lot of causes — and that's progress!

🚛 Real-World Examples in Emissions Systems

  • DEF Pump wiring faults — often intermittent and related to loose pigtail connections.
  • NOx sensor failures — chafed wires near the mounting point.
  • DPF pressure sensor issues — fault when the connector is wiggled or when the harness is tapped.

🛡️ Final Advice: Be Methodical, Not Lucky

Intermittent faults are solved by methodical troubleshooting — not by guessing. Take your time, make notes, and approach it step by step.

And if you’re ever stuck, contact us for expert help with your emissions system troubleshooting!

✅ Final Thoughts 💡

Intermittent electrical faults in emissions systems can be a major headache, but with a structured, logical approach, they become much easier to diagnose. Focus on wiring issues, inspect fastening points, perform wiggle and tap tests, and always understand how the system works before diving in. This method will save time, reduce frustration, and get the equipment back up and running faster! 🏆🚜

For more expert tips and high-quality emissions system components, visit www.aftertreatmentparts.com! 🛒⚙️

 

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