Description

Liebherr LTM 1090/3 Diagnostics Manual – Factory Test Programs and Error Codes

I have seen more seal failures from guessing than from wear. You start a Liebherr LTM 1090/3 and it throws a code you don’t recognize – your first move better not be swapping parts. Without the factory Liebherr LTM 1090/3 Diagnostics Manual, you are flying blind. This 106-page OEM document gives you the exact test sequences Liebherr dealerships run. No third-party interpretation, no missing pages. If you’re a field tech or an owner-operator who wants to stop chasing ghosts, you need this on your tablet or printed out.

Let’s talk about what is inside. The manual is built around the chassis test program. You get a full test program overview, then a detailed description of how to activate it in ENGINE ON or ENGINE OFF mode. It explains switching between individual tests, starting and stopping them, and menu navigation. General information and test display layout are covered in the first few sections. For a crane that communicates through a keypad unit, display unit, and support control unit, this is the Rosetta stone.

Liebherr LTM 1090/3 Diagnostics Manual: Test Program Overview

From the table of contents, you’ll see Section 3 “All test programs” is the meat. It starts with tests on the support control unit – data transfer between I/O module and support control unit, pilot lamp test, key test. Then the keypad unit tests (02 through 08) cover every button, output, and data link. Display unit tests (10–12) do the same for the 7-segment displays and bar diagrams. If your heating servomotors are acting up, Test 13 and 14 walk you through position of installation and function. Active rear axle steering gets five separate tests – special diagrams, manual steering in test mode, angle sensor zeroizing, centering circuit function, and locking/centering valve function. That is the kind of granularity aftermarket manuals skip.

Engine ON and Engine OFF Mode Activation

This is something you will use every time. The manual gives two activation paths: one with the engine running, one with the key on but engine off. That matters because certain tests – like engine overspeed protection (Test 40 and 41) – require the engine to be running. Others, like checking the keypad unit inputs, you can do with the ignition on. Starting and stopping the test program has its own procedure so you don’t brick the control unit. Write that procedure on a card until you have it memorized.

Over 70 Individual Tests: Keypad, Display, Steering, and Hydraulics

Count them. Section 3 contains more than seventy numbered tests. You get everything from vehicle lights test (Test 04) to front axle steering hydraulics (Test 73). The manual organizes them by system – support control unit first, then keypad, then display, then chassis systems like active rear axle steering, engine overspeed protection, hydrostatic fan drive (Tests 43 and 44), and clearing the error code memory for ECU, TCU, AAS and intarder. There is even a dedicated test for checking the function of the ASR-DIF valve (Test 62) and wheel speed of the ABS speed sensors (Test 63). If your crane has a AAS sensor that is out of range, Tests 60 and 61 tell you how to test the assignment of AAS sensors and valves with a pulse program.

Don’t confuse this with a generic On-board Diagnostics (OBD) scan. This is a proprietary test program that interfaces directly with the Liebherr control units. Unlike a Manual Transmission where you can measure end play with a feeler gauge, these tests require you to follow the exact steps in the manual. Skip a step and you might get a false pass.

Engine Overspeed Protection (Test 40 and 41)

These two tests are critical for anyone running the crane under load. The manual shows you how to simulate an overspeed condition safely and verify that the ECU cuts fuel. It also covers clearing the fault memory after you fix the root cause. Page 73 lists the specific pressure values for the fuel system during the test – but if you are ordering the manual, look for the exact table in the hydraulics supplement. Don’t rely on internet numbers.

Hydraulics Tests Supplement: Pressure Values and Diagrams

After the test programs, there is a dedicated Hydraulics Tests Supplement with connection plug centre console overview, pressure sensor connection diagrams, and a table of pressure values. Tests 70 through 73 are the ones to focus on for hydraulic issues: support hydraulics, active rear axle steering hydraulics, front axle steering hydraulics, and axle spring-mounting function. If your outriggers won’t set or the rear axle wanders, those tests with the pressure values from the supplement will isolate the valve or sensor faster than swapping parts.

Error Codes – Main Code/Sub Code Routines for Liebherr CH

The back of the manual covers error codes. You get main code/sub code test routines specific to Liebherr CH and an error code table for hardware components. This is not a generic SAE J1939 list – these are proprietary Liebherr codes that the display unit or keypad will show. When you see “Main 12 Sub 3”, you look it up here. For deeper cross-referencing, pair this manual with the Liebherr LTM 1090-4.1 Liccon Error Code Manual and the Liebherr LICCON 1 Diagnosis Manual.

If you need the chassis test program in isolation, the Liebherr LTM 1090/3 Chassis Test Programs manual is a separate product that focuses only on the steering and support tests. But for a full diagnostics workflow, you want this manual.

FAQ

Is this manual suitable for someone new to Liebherr cranes?

If you don’t know the difference between a support control unit and a keypad unit, start with the operator’s manual. This is for diagnostics.

Does it cover the engine control system?

Yes. Tests 40 and 41 specifically cover engine overspeed protection, but the manual assumes you have basic engine knowledge. It does not include the engine service manual — it focuses on the chassis test program that interacts with the engine ECU. You’ll see references to clearing error code memory for ECU, TCU, AAS and intarder. That is the extent of engine coverage. For full engine rebuild specs and torque values, you need the separate engine manual. Your local dealership might carry that, but it is not in this document.

Are there wiring diagrams?

Yes, in the Diagrams section. You get diagrams for keypad unit, display unit, and support control unit connections. Not full vehicle harnesses, but enough to pin-test modules.

Can I use this manual to troubleshoot hydraulic failures?

Absolutely. The Hydraulics Tests Supplement section gives you pressure sensor connection plug diagrams for the centre console, and a table of pressure values. Tests 70 through 73 cover support hydraulics, active rear axle steering hydraulics, front axle steering hydraulics, and axle spring-mounting function. If you have a dead outrigger or a steering that wanders, you run these tests with the crane’s onboard diagnostics interface. The manual tells you exactly which pressure to expect at each sensor when commanded. That is the kind of spec you do not get from a third-party copy. This is factory original. Pair it with a good pressure gauge set and you can isolate a failed solenoid or a blocked line in under an hour.

Don’t waste billable hours chasing ghosts. Access the Factory Manual and get the exact test procedure that Liebherr dealerships use.