Description

Mercedes-benz 508 Technical Manual – Traction Control 4ETS Part 5

You are staring at a 508 with a traction control light that won’t clear. The generic scanner says something about the 4ETS system, but you need the actual logic. I’ve been turning wrenches for 28 years, and I’ll tell you straight—this Mercedes-benz 508 Technical Manual is not a whole-truck repair guide. It’s a 13-page factory training document that goes deep into the 4ETS traction control system. Period. If you are troubleshooting a 508 that cuts power on acceleration or has erratic brake intervention, this is the paper you need.

I’ve been burned by aftermarket manuals that guess the block diagram and reprint the wrong valve body layout. This one comes from Mercedes-Benz USA, LLC, copyright 2000. That’s original OEM training material. The OCR excerpt shows the legal disclaimer: “These technical training materials are current as of the date noted… you must always refer to the latest Mercedes-Benz Technical Publication and follow all pertinent instructions.” That is exactly the kind of source validity you want when a customer’s safety is on the line.

For reference, if you need the full service schedule or engine torque specs, check the Mercedes-Benz 508 Traction Control ESP Technical Manual or the Mercedes-Benz 508 Traction Control ABS Service Manual. For older hydraulic control systems, the Mercedes-Benz 508 ETS-ASR Technical Manual covers a different generation.

Brake Torque Control Range

Page 5 of this manual gives you the exact control ranges. Rear axle control is active from 0 to about 80 km/h (50 mph), and may remain active up to 130 km/h (80 mph). Front axle control runs from 0 to 40 km/h (25 mph), with a possible extension to 80 km/h (50 mph). If you are not seeing intervention at the expected speeds, you need to verify the wheel speed sensors and the brake torque control module. Those numbers are not guesswork—they are factory calibrated. I’ve seen shops replace an entire ABS pump because they did not check the control range first. That is a wasted Saturday.

4-ETS Block Diagram: System Overview

Chapter 4-ETS Block Diagram lays out the communication between the wheel speed sensors, the brake pressure modulator, and the engine control unit. The diagram shows how the system intervenes on the front and rear axles separately. If you are chasing a code for “implausible signal,” trace it through this block diagram. The manual also references the N78 control unit, which is the traction control module on these trucks. Do not trust aftermarket wiring diagrams for that—they often swap pinouts between model years.

Need a refresher on how a Manual Transmission interacts with the transfer case? The Manual Transmission page on Wikipedia gives a general overview, but this manual covers the specific 4ETS interaction with the transfer case. The two are linked through the torque distribution logic, and the manual explains the oil supply and high/low range selection.

Transfer Case Function and Oil Supply

The Transfer Case Function section describes the hydraulic and mechanical elements that split torque between front and rear. The oil supply system is critical—low fluid can cause the transfer case to lag, which the 4ETS interprets as wheel slip, triggering unwanted brake torque. The manual shows the oil path and the check valves. If you have a customer who complains of a shudder on tight turns, check the transfer case oil level before you touch any electronics. I’ve fixed three 508s this year with nothing but a fluid top-up.

What Does the M-Class Transfer Case Section Cover?

This manual includes a specific subsection titled M-Class Transfer Case, covering the ML320, ML430, and ML55. The block diagram for the transfer case identifies the N78 controller and the solenoids for high/low range shift. For a DIYer working on an ML series, this section is gold. It tells you the control logic for the shift motor and the position sensor. Without that logic, you are chasing a ghost. The manual also lists torque values for the transfer case mounting bolts? No, it does not. This is a training manual, not a step-by-step repair guide. That said, the Manual Transmission knowledge helps understand the gear reduction, but the 4ETS control is what makes this truck unique.

High/Low Range Selection – Why It Matters

The High/Low Range Selection page explains the interaction between the transfer case shift and the 4ETS logic. When the driver selects low range, the system recalibrates the brake torque control thresholds. If you wire a new shift motor and do not recalibrate the 4ETS control module, the system will throw a code and disable traction control. The manual does not give a procedure for recalibration—that is in the WIS—but it does explain why the system behaves the way it does. That saves you from swapping parts that are fine.

This is a 13-page manual. It will not teach you how to rebuild an engine. But if you are in the middle of a 4ETS diagnosis, those 13 pages will point you to the root cause faster than any third-party PDF. I keep a copy next to my scan tool.

Audience Fit: Who Actually Needs This?

DIYers who own a 508 or an early ML320/430/55 will find the system descriptions useful for understanding why the ABS pump runs when it shouldn’t. Professional technicians will appreciate the factory block diagrams and the control range data. Shop owners: hand this to a junior tech before he starts throwing parts at a traction control code. It will save you the cost of a return visit. Beginners should have a basic understanding of electrical circuits before diving in.

Source Authenticity: OEM vs Aftermarket

Every page of this manual is original Mercedes-Benz training material. The copyright is owned by Mercedes-Benz USA, LLC. No reprints, no third-party formatting. The OCR excerpt shows the exact disclaimer about model variances and the need to check WIS. I have seen aftermarket manuals that copy the block diagram but remove the torque range numbers. That is dangerous. If you need the charge pressure spec or the exact control speed, you want the factory source.

Does this manual include engine torque specs or repair procedures?

No. It only covers the 4ETS traction control system.

What brake torque values are listed, and can I use them for diagnostic testing?

The manual gives the speed ranges at which brake torque control is active on each axle (rear: 0–80 km/h, front: 0–40 km/h). These are not bolt torque values; they are control logic thresholds. You use them to verify that the system is commanding brake pressure within the intended speed window. Aftermarket manuals often omit these thresholds, leading techs to misdiagnose wheel-speed sensor faults as hydraulic failures. The factory range data on page 5 also notes that control may remain active up to higher speeds under certain conditions, which helps explain intermittent code setting.

If you are working on a 508 and need to sort out a traction control issue without burning billable hours, stop guessing. Access the Factory Manual.