FAQ
TL;DR: 580,000 km case: “the smoke-with-thermometer light means high exhaust gas temperature.” If it clears after a steady drive, it aligns with normal DPF regeneration; if it repeats, scan the truck and check EGR/EGT/DPF sensors. [Elektroda, szyniu, post #17790233]
Why it matters: This FAQ helps MAN TGX Euro 6 drivers diagnose a recurring hot‑exhaust icon and prevent costly aftertreatment damage.
Quick Facts
- The thermometer-in-smoke icon indicates elevated exhaust temperature during DPF regeneration; avoid stopping on flammable surfaces until it clears. [“MAN TGX Euro 6 Operator’s Manual”]
- During active regeneration, exhaust gas temperature can exceed 500°C; keep the exhaust area clear of people and combustibles. [Bosch, 2014]
- Frequent re-ignitions can point to EGR issues; unresolved EGR faults can escalate engine risk. [Elektroda, kakibara, post #17061880]
- The dash may show the icon without a numeric fault; connect a diagnostic computer to confirm regen status or stored errors. [Elektroda, sebastian607, post #17061296]
- Typical AdBlue usage is about 3–5% of diesel consumption; normal draw suggests SCR is functioning as expected. [“MAN Truck & Bus — AdBlue: Q&A”]
What does the thermometer-in-smoke icon on a MAN TGX Euro 6 mean?
It indicates the exhaust aftertreatment is very hot because the DPF is regenerating. The system raises exhaust temperature to burn soot in the filter. Continue driving and avoid parking on flammable surfaces until the lamp clears. The icon turns off once temperatures fall after regeneration completes. [“MAN TGX Euro 6 Operator’s Manual”]
Why does the light turn off after about 30 km of driving?
A steady drive allows the engine to reach operating temperature and sustain the conditions needed for automatic DPF regeneration. When soot burn-off completes, exhaust temperature drops and the icon extinguishes. If the light reappears frequently in short intervals, schedule diagnosis to check load, sensors, or EGR performance. [“MAN TGX Euro 6 Operator’s Manual”]
Is it safe to keep driving when that hot-exhaust light appears?
Yes. Keep driving so regeneration can complete. Follow the safety instruction: “Do not park on readily flammable surfaces.” Avoid idling or shutting down mid‑regen if possible. The light should clear when the DPF finishes burning off soot. If it persists or the engine lamp joins, scan for faults. [“MAN TGX Euro 6 Operator’s Manual”]
Which sensor is the main information provider for this warning?
Engine management uses multiple inputs: exhaust gas temperature sensors (before/after the DPF) and the DPF differential pressure sensor. High EGT during an active regen is expected; abnormal readings or pressure signals can trigger warnings or repeated regens. “DPF regeneration demands high exhaust temperatures.” [Bosch, 2014]
How do I complete a regeneration quickly and safely on the road?
- Warm the engine fully, then maintain steady, moderate load at road speed.
- Keep driving without prolonged idling or stop‑and‑go until the icon clears.
- Do not park on combustible surfaces while the hot‑exhaust warning is on. [“MAN TGX Euro 6 Operator’s Manual”]
I changed the EGR cooler and the icon now lights often. What should I check?
Check for residual coolant contamination, EGR valve sticking, and leaks that raise soot formation. Verify DPF soot load and inspect EGT and differential pressure sensor plausibility. Repeated hot‑exhaust indications after EGR service strongly suggest EGR malfunction or related aftertreatment stress. Address it promptly to prevent further damage. [Elektroda, kakibara, post #17061880]
The engine lamp is on, but no code shows on the cluster. What should I do?
Not all faults display as text codes on the dash. Connect a diagnostic computer (e.g., MAN‑cats or equivalent) to read stored engine, aftertreatment, and chassis module faults. This confirms whether the event was a normal regen or a fault condition that needs repair. [Elektroda, sebastian607, post #17061296]
What do TCU 00191-08, DIAG 03404-02, and ZBR 03500-00 mean?
Those are module-specific fault identifiers from the transmission (TCU), diagnostic manager (DIAG), and central body module (ZBR). Their meanings depend on the vehicle’s dataset. Use MAN‑cats to read full descriptions, freeze‑frames, and standard SPN/FMI equivalents for correct troubleshooting. [“MAN-cats II Diagnostic System — User Guide”]
Does AdBlue usage affect this hot-exhaust icon?
The icon relates to DPF regeneration, not SCR dosing. That said, normal AdBlue consumption around 3–5% of diesel indicates SCR is working. Abnormal AdBlue faults may trigger the engine lamp, but they do not directly cause the hot‑exhaust symbol. Diagnose both systems if warnings persist. [“MAN Truck & Bus — AdBlue: Q&A”]
What edge cases cause the light to stay on or recur frequently?
Edge cases include failed EGT sensors reporting implausible values, blocked DPF pressure hoses, or excessive soot from air/EGR faults. A sensor stuck low may prevent regeneration; one stuck high can trigger repeated regens. Inspect sensors and pressure lines before condemning the DPF. [Bosch, 2014]
How can I tell a regeneration is happening besides the icon?
Expect the hot‑exhaust icon and driver notification. Engine management may adjust fueling and exhaust temperature control. The key action is to keep driving until the indicator clears. If messages repeat without clearing, have the system checked with a diagnostic tool. [“MAN TGX Euro 6 Operator’s Manual”]
What’s the best first diagnostic when the icon appears often?
Scan the engine and aftertreatment with a proper tool. Record DPF soot load, differential pressure, EGT sensor values, and regen counters. Review freeze‑frames for operating conditions and fault frequency. This narrows whether you face normal regens, sensor errors, or hardware issues. [“MAN-cats II Diagnostic System — User Guide”]
