What This Modulator Actually Does
This isn't just a solenoid block – it's the ECU and the pneumatic modulator built into one housing, which is how Wabco set up the TCS II generation. It reads the wheel speed sensors, decides when a wheel's about to lock, and cracks the modulator valves to hold or release air at the brake chambers. On 2S/2M trailers you're running two sensors and two modulator channels; 4S/2M adds two more sensors but keeps two channels. This part covers both configs depending on how it's wired at install.
It bolts to the frame rail, usually near the front axle, with the harness running back to the sensors and forward to the trailer's power/ABS connector. If you're pulling a reefer, dry van, or flatbed built in the 12V TCS II era, this ECU is a common failure point once it's a decade or more old – connectors corrode, internal relays stick, or the unit just stops talking to the sensors.
Reading the Cross-Reference Numbers
The Wabco 4005001030 and S4005001030 are the same part – Wabco just prefixes some of their reman or service-stock units with an 'S.' Rockwell International's S4005001037 is a licensed cross from back when Rockwell and Wabco shared trailer ABS architecture; the last digit change (30 vs 37) reflects a running production update, not a different function. Dorman's 599-7002 and Torque's TR4005001030 are aftermarket-built units designed to bolt in and wire the same way. Newstar's S-25213 is another aftermarket cross carrying the same fitment.
None of these swap in blind. Before you order, pull the tag off your existing ECU – it'll have a Wabco part number or an 'S' prefix number stamped right on the housing. Match that number, not just the trailer make or year, because trailer builders mixed ABS suppliers and generations depending on when the trailer came off the line. If the number's worn off, check your trailer's ABS placard or wiring diagram sticker, usually near the ECU or on the frame rail.
Also confirm sensor count and channel config (2S/2M vs 4S/2M) matches what's currently wired in. Wrong config means the ECU won't read all your sensors correctly even if it physically bolts up.
Ordering From PartStop
We stock this one in Tacoma and can usually get it across the counter same day if you're local – handy when a trailer's sitting at a dock waiting on an ABS fault to clear. Ship nationwide runs 1-3 days depending on where you're at.
Every unit comes with our standard 6+ month warranty. Confirm your VIN or pull the old part's stamped number before you order – trailer ABS ECUs are not a part you want to guess on, and returns on electrical components get complicated once they've been wired in.
4005001030 Cross-Reference & Interchange Numbers
These manufacturer and aftermarket numbers commonly cross-reference to 4005001030. Use them to identify the part — then confirm the exact fit by VIN or the number stamped on your old unit before you order. An interchange is a starting point, not a fitment guarantee.
| Brand / Line | Cross-Reference Numbers |
|---|---|
| Wabco | S4005001030 |
| Rockwell International | S4005001037 |
| Dorman | 599-7002 |
| Torque | TR4005001030 |
| Genuine Newstar | S-25213 |
Frequently asked questions
Does 4005001030 fit my trailer?
Probably, if your old ECU is stamped 4005001030 or S4005001030. Trailer builders used different ABS suppliers and generations even within the same model year, so match the number off your old unit or check the ABS placard/wiring sticker on the trailer rather than going by year alone.
Is this the same as the Rockwell S4005001037?
Close, not identical. They're cross-licensed same-generation parts, but the number difference reflects a production running change. Physically and electrically they interchange in most applications, but confirm against your original tag before ordering.
Can I use the Dorman 599-7002 instead of the Wabco number?
Dorman builds it as a direct replacement for the same application, wired the same way. Aftermarket units like this typically run less than the Wabco-branded part and carry our 6+ month warranty, but always match sensor config (2S/2M or 4S/2M) to what's currently on your trailer.
Not sure it fits? We check before you pay.
Run your VIN and we’ll match parts to your exact truck, or call the counter — a person who knows trucks verifies fitment by OEM number before the order ships. No wrong-box returns.
More cross-reference guides
Need the part, not just the reading?
Every part below is a Premium Quality aftermarket Direct Replacement with published OEM cross-reference numbers, a 6+ month warranty and same-business-day shipping from Tacoma, WA. Not sure it fits? Run your VIN — or call and a person who knows trucks will verify fitment before you pay.