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Nie, dziękuję Przekieruj mnie tamFrom automatic mode goes to manual when change to single gears. Why?
‐ On a MAN TGX with the ZF AS-Tronic / TipMatic automated manual transmission the control logic is designed to leave “A” (automatic) and enter “M” (manual) in two situations:
Key points
• Behaviour is normal when you really touch the ± selector.
• If it happens without you touching the lever, the logged code 03155-00 points to a range-selector malfunction (air leak, sticking solenoid, bad sensor or wiring).
• Correct diagnosis requires MAN-cats III (or equivalent) live data, actuator test and pneumatic leak check.
Transmission architecture
• AS-Tronic 12-speed = 3-speed main box × 2-speed splitter × 2-speed range.
• Gears 1-6 are “low range”, 7-12 are “high range”.
• The range shift (6↔7) is the heaviest action: a pneumatic cylinder moves the range sleeve while the main box moves from 3rd to 1st.
TCU operating modes
• Automatic (A): TCU chooses gears by load, speed & gradient.
• Manual (M): Driver commands precise gear; TCU only checks rev/torque limits.
• Mode change triggers:
– Electrical signal from the selector when ± is pressed (normal).
– Internal fault routine when a commanded shift is not confirmed (failsafe).
DTC 03155-00 – “Transmission range selector, malfunction”
• Set when the position sensor on the range fork does not agree with the command within ~700 ms.
• Consequence: TCU stores code, illuminates gearbox lamp, switches to “M”, keeps currently engaged gear or neutral.
Root-cause tree for 03155-00
High probability
• Pneumatic leak in lines to range cylinder (soap-water test).
• Contaminated / under-lubricated range cylinder ⇒ sluggish stroke.
• Sticking or electrically open-circuit range solenoid in the mechatronic block.
Medium probability
• Failed range position sensor (Hall or inductive).
• Broken/chafed wires or corroded pins at the round 28-pole gearbox connector.
Lower probability but costly
• Worn synchroniser ring, bent range fork, cracked sleeve inside the box.
Diagnostic workflow (field-proven)
a) Record symptoms: when, how often, air pressure reading, ambient temp.
b) Read TCU with MAN-cats → freeze-frame data for 03155 (engine rpm, air pressure, commanded vs. actual range).
c) Live-data test while forcing range shift with wheels lifted: watch Range Solenoid Cmd, Range Position.
d) Actuator test: energise solenoid → listen/feel for click & air discharge.
e) Leak detection: isolate gearbox air supply, pressurise to 8 bar, observe gauge drop, spray joints with soap.
f) Electrical checks: insulation and continuity of range solenoid + sensor, load test >1 A, inspect connector cavity.
g) If pneumatics/electrics pass but fault persists, remove top cover, inspect range fork & sleeve for scoring.
• New MAN TG3 models use ZF TraXon with an integrated electro-hydraulic actuator. Range-selector faults are rarer, but the same failsafe philosophy (drop to manual) remains.
• Remote telematics (MAN ServiceCare, ZF SCALAR) can now send DTC 03155 directly to the workshop, reducing downtime.
• After 2022 MAN introduced a TCU software ref. “F-164.04” that lengthens the timeout for the range confirmation by 150 ms to reduce nuisance drops to “M” in cold climates—check if an update is available.
• Analogy: Think of the TCU like a pilot’s autopilot. The moment you nudge the yoke (± gear), it disconnects. If the autopilot tries to bank but the aileron servo jams (range cylinder), it also disengages and asks you to fly manually.
• Engine-over-rev protection: even in “M” the TCU will refuse destructive shifts; driver still cannot select 4th at 90 km h.
• Driving long distances with a known gearbox failsafe can strand the vehicle (stuck in neutral) and breach EU Regulation (EC) 765/2009 on in-service vehicle safety.
• Workshop must lock-out and depressurise air system before working on solenoid pack (EN 12195-1).
• If the selector is bumped by the driver’s hand, the behaviour is 100 % normal and not a fault.
• Continuous driving in manual with a partially failed range unit can accelerate internal wear; plan repair promptly.
‐ Compare failure statistics between AS-Tronic and newer TraXon actuators regarding pneumatic vs. electro-hydraulic design.
‐ Investigate predictive maintenance using pressure-decay signatures to warn of impending range-cylinder leakage.
‐ Explore retrofit of filtered, heated air supply to transmissions operating in very cold, humid regions.
Your TipMatic transmission switches from “A” to “M” because:
