MAN TGX Euro 6 Error 5 05787-08: Turbo Actuator Temperature Signal Fault

User question

Eroare man tgx e6 5 05787-08

Artificial Intelligence Response

Direct answer to the question

• Code 5 05787-08 on a MAN TGX Euro 6 is best interpreted as J1939 SPN 5787 FMI 08: Engine turbocharger wastegate/VTG actuator “2” temperature – signal with abnormal frequency/pulse width (implausible/intermittent). This points to a sensor/electronics or wiring issue around the turbo actuator rather than NOx, EGR or EBS. (scribd.com)
• Key points
  • SPN 5787 = turbocharger wastegate/actuator temperature (instance 2). (scribd.com)
  • FMI 08 = abnormal frequency/pulse width → often intermittent signal, broken wire, poor ground, or failing sensor/electronics. (spnfmi.com)
  • “5 xxxxx-yy” is the display format; MAN’s public web does not publish a free, official cross-table for these, so confirm with MAN-cats III/IV when possible. (manerrors.com)

Detailed problem analysis

• Why this mapping is the most consistent

  • The numeric core “05787” aligns exactly with J1939 SPN 5787, which SAE assigns to the turbocharger wastegate actuator temperature parameter set (instance 2). This is documented in J1939 SPN lists and in actuator vendors’ J1939 manuals. (scribd.com)
  • FMI “08” is a generic J1939 failure mode meaning abnormal frequency/pulse width/period; practically this shows up as an implausible or erratic sensor signal seen by the ECU. (spnfmi.com)
  • Several circulated interpretations (NOx sensor, EBS modulator, generic EGR) do not match the SPN 5787 assignment and are therefore unlikely for this exact code, even though those subsystems are common failure sources on Euro 6 trucks.

• What component is involved on a TGX E6

  • Euro 6 MAN engines (e.g., D26/D38 families) use electronically controlled turbocharger hardware (variable turbine geometry or wastegate actuation). The actuator assembly typically contains position sensing and an internal temperature sensor; the engine ECU monitors that temperature to protect the actuator/electronics. SPN 5787 flags that temperature-signal path for the second instance (on twin/2‑stage setups, or manufacturer-specific channel indexing).

• Typical root causes for FMI 08 on this circuit

  • Harness/connector damage near the turbo due to heat, oil mist, water ingress, or chafe → intermittent signal (“abnormal frequency”).
  • Failing actuator electronics (internal sensor/reference fault).
  • Power/ground/reference instability (5 V ref dropouts, shared sensor return issues).
  • Less common: ECU pin/circuit fault.

• Operational symptoms you may see

  • Turbo control faults, reduced boost authority, limp/derate under load, turbo protection strategies activating, MIL/engine warning, possibly companion codes for turbo position control or boost deviation.

Current information and trends

• Open manufacturer cross-references for MAN’s “5 xxxxx-yy” display are not publicly maintained online; technicians generally correlate to J1939 SPN/FMI and then verify with MAN-cats. (manerrors.com)
• Vendors of turbo actuators publish J1939 parameter maps that explicitly include SPN 5787 (Actuator 2 Temperature), confirming the SPN assignment used in the field. (de.scribd.com)
• Industry trend: heat-related wiring failures around turbo/aftertreatment areas have increased with Euro 6 thermal loads; OEMs periodically update heat shielding and loom routing.

Supporting explanations and details

• Signal path
  • The actuator’s internal sensor reports a temperature value over an analog or digital channel monitored by the ECU. FMI 08 indicates the ECU sees a pulse/frequency characteristic out of spec (e.g., intermittent, noisy, or missing timing), which frequently traces back to wiring/connector issues rather than a steady “high/low” level failure.
• Why “Actuator 2”?
  • J1939 defines multiple instances so one engine can expose more than one actuator. Some single‑turbo engines still map as instance “1,” while twin or staged systems may use “1” and “2.” The MAN ECU may number its internal channels accordingly; confirm with live data which physical actuator channel is flagged. (scribd.com)

Ethical and legal aspects

• Do not disable or bypass emissions/turbo controls. Tampering with emission-related components (EGR/SCR/OBD strategies) is illegal in many jurisdictions, including the United States, and can create safety and liability issues.

Practical guidelines

• Confirm the code properly
  • Read the DTC as SPN/FMI with a J1939-capable tool (MAN-cats III/IV, TEXA, Jaltest, etc.). Save freeze-frame data (coolant/EGT, boost, actuator position, supply voltage) to correlate operating conditions at fault occurrence.
• Visual/thermal inspection (engine cold)
  • Inspect the turbo actuator harness from the actuator back to the main loom: look for brittle insulation, chafe on brackets/edges, oil contamination, and any melted conduit. Gently tug-test each wire at the connector, check for pin push-back/corrosion.
  • Verify heat shields, clips, and standoffs are present and correctly fitted.
• Electrical checks
  • With key ON, verify actuator supply and ground integrity (voltage drop under a small load, not just open-circuit voltage). Many sensing circuits use a 5 V reference; confirm ref and return stability with a scope if available.
  • Wiggle test the harness while monitoring the live temperature parameter for dropouts/noise (this directly targets FMI 08-type faults).
  • If you can access the ECU side, check continuity and insulation resistance actuator ↔ ECU; repair any high-resistance/short-to-ground spots.
• Functional checks
  • Command an actuator sweep/test with the scan tool; monitor commanded vs actual position and the internal temperature reading. A flatlined or wildly jumping temp channel indicates sensor/electronics trouble.
• Isolation strategy
  • If the platform uses two actuators and they are physically interchangeable (verify PNs first), a left/right or stage-1/stage-2 swap test can localize the fault to the actuator vs. the truck harness. Re-run the test and see if the code follows the hardware.
• When to replace the actuator
  • Replace if wiring, power/ground, and connector integrity are proven good and the internal temp signal remains erratic. Perform any required initialization/calibration after replacement and re-check for codes.
• After repair
  • Clear DTCs, perform a controlled road test under load (monitor boost, actuator position, and actuator temperature signal stability). Re-scan for pending/active faults.

Possible disclaimers or additional notes

• MAN’s instrument-cluster “5 05787-08” display is a human-readable form; the authoritative diagnosis is the ECU’s SPN/FMI. Because MAN does not publish a free, official cross table online, always validate with MAN-cats if available. (manerrors.com)
• If your engine is a single-actuator VTG, “Actuator 2” may reflect a manufacturer channel index rather than a second physical unit—use live data naming to identify the physical part.

Suggestions for further research

• Retrieve full SPN/FMI snapshot plus any companion codes (boost deviation, actuator position control errors).
• Check for MAN service bulletins addressing heat shielding or loom reroutes near the turbo on your exact engine (D26 vs D38) and VIN.
• If recurrent, consider adding/upgrading thermal sleeving on the repaired section of harness.

Brief summary

• Most consistent technical reading for 5 05787-08 is: turbo actuator temperature signal (SPN 5787) with FMI 08 (abnormal frequency), typically caused by wiring/connector damage near the turbo or a failing actuator’s internal sensor/electronics—not NOx/EGR/EBS. Inspect/repair the harness, verify power/ground, run an actuator test, and replace the actuator only after electrical integrity is confirmed. (scribd.com)

If you can share the engine type (D26 or D38), year/VIN, any companion codes, and whether the fault appears hot, cold, or under load, I can tailor the pinouts and test values to your exact configuration.

Disclaimer: The responses provided by artificial intelligence (language model) may be inaccurate and misleading. Elektroda is not responsible for the accuracy, reliability, or completeness of the presented information. All responses should be verified by the user.