Low Voltage, High Headache: Diagnosing a LiquidSpring Suspension Failure

Because when your rig rides like a dump truck, nobody's having a good day—especially not the crew in the back.

Had a call for a rig with a LiquidSpring suspension that just wouldn’t wake up. One of those “it used to work fine” kind of problems. Sure. Heard that one before. Here's how the troubleshooting unfolded—and what you should keep in mind if you're chasing electrical ghosts in a smart suspension system.

Step 1: Start With What the System Tells You

Plugged in, pulled codes. Got a low voltage DTC from the system—not a great sign, but also not the end of the world. First step in chasing a low-voltage gremlin? Go to the source.

Main 80A fuse? Checked.
Voltage across it? 13.6V—right where it should be.
Frame ground? Looked like it spent a week in a salt mine. I disassembled the ground connection, hit it with a wire brush until it shined like a new penny, and reinstalled with a fresh bolt and dielectric grease. Still no go.

So voltage is good upstream, but the system’s still acting like it’s on life support.

Step 2: Follow the Current Downstream

Next stop: the ECU. I checked voltage at the harness where power enters the ECU.

Only 6 volts.
Yeah, that’ll do it.

Now, I know LiquidSpring systems are sensitive to voltage drops. Anything under spec and the current draw spikes. That spike leads to heat. And heat? That leads to bad days and fried components.

So I opened up the split loom running between the battery and the ECU—and bingo.

Step 3: The Hidden Corrosion Trap

Found a main power splice in the loom. One of those inline crimp jobs wrapped in old electrical tape from the factory. Cut it open and it was packed with corrosion. Looked like it had been pulling juice through a sponge.

I cut out the splice entirely and soldered in a new section of wire. Heat shrink, adhesive lined, the whole nine. Voltage back at the ECU? Clean 13.6V.

Hit the switch again—and this time, the pump motor came to life.

But... no ride height change. Truck just sat there like a stubborn mule.

Step 4: Swapping the Brain

This is where experience kicks in. Low voltage doesn’t just make the system underperform—it can kill the ECU. Long-term undervoltage leads to heat buildup, especially in solid-state components, and that can silently cook the board from the inside out.

Luckily, I carry a spare LiquidSpring ECU for moments like this. Swapped it in.

And just like that—bam. System fully online. Suspension responded. Ride height adjusted. Done and done.

Takeaways From the Field

Here’s what this job reminded me (again):

• Voltage drop isn’t just a nuisance—it’s a silent killer.
  If you're getting anything less than battery voltage at the ECU, you've got resistance somewhere in the harness. And that resistance is stealing performance—and possibly frying components.

• Don't trust splices. Ever.
  Especially the buried factory ones in older rigs. Corrosion loves hidden places, and LiquidSpring systems draw real power. Every splice is a potential bottleneck.

• Carry known-good test parts.
  If you’re working in the field and have a spare ECU, save yourself time. Swapping in a known-good module can make or break your diagnosis—especially when you're losing daylight or the customer’s losing their patience.

• Grounds are king.
  Dirty or loose grounds = unreliable systems. Period. Always clean, always check, always grease.

Final Word

Suspension systems like LiquidSpring are smart. But they’re only as smart as the power they get. Don’t let your diagnostics stop at “fuse is good”—you’ve got to chase the electrons all the way to the module. Bad connections cost more than time—they cost components.

And if you’re a fleet tech or shop owner reading this, do yourself a favor: add checking power and grounds to your standard PM checklist. Catch this stuff early and you won’t need a spare ECU in the first place.