FAQ
TL;DR: Mercedes Vito W639 power loss with P0105 often traces to the boost/MAP circuit; this van uses 2 pressure sensors, and as one expert notes, "It must be original." Check sensor, wiring, vacuum, actuator, or turbo geometry. [Elektroda, diodabg, post #17026105]
Why it matters: This FAQ helps Vito 639 owners quickly pinpoint no‑power + P0105 causes and safe fixes.
Quick Facts
- P0105 on Vito 639 relates to the boost/MAP sensor and can log “too high voltage.” [Elektroda, Fokus1981, post #17029983]
- Typical symptoms: sudden loss of power, limp to ~3,000 rpm, sometimes after ~700 m of driving. [Elektroda, solek_87, post #16770751]
- The Vito W639 employs 2 pressure sensors; using genuine parts avoids misreads. [Elektroda, diodabg, post #17026105]
- Confirm wiring: test the 3 MAP wires in parallel and also the turbo valve wiring. [Elektroda, jurekk55, post #16771149]
- Proven fixes reported: turbo geometry and sensors refurbishment; in one case, parking heater fault cleared P0105. [Elektroda, tomas0507, post #18669429]
What does code P0105 mean on a Vito 639?
P0105 flags a boost/MAP sensor circuit fault. Owners report “too high voltage” with limp mode. Expect reduced power and limited revs. Clear the code only after fixing the cause. Inspect sensor, wiring, vacuum control, and turbo actuation before replacement. [Elektroda, Fokus1981, post #17029983]
Where is the Vito W639 boost/MAP sensor located?
One pressure sensor sits on the charge pipe near the intercooler with access from underneath. The Vito uses two pressure sensors, so verify you are testing the correct unit and use an original‑quality sensor to avoid bad data. [Elektroda, diodabg, post #17026105]
What are classic symptoms when P0105 appears?
Drivers report sudden power loss, no acceleration, and revs capped near 3,000 rpm. Some note the issue starts after about 700 meters, then persists with a check light. Restarting may temporarily restore power before the fault returns. [Elektroda, solek_87, post #16770751]
How should I start diagnosing P0105 on the road?
“Diagnose while driving.” Log boost request vs. actual, then check the turbo control harness and vacuum lines under load. A short drive with live data quickly narrows sensor, wiring, or actuator faults without guesswork. [Elektroda, diodabg, post #17026138]
Which quick checks have owners already tried and should I repeat?
Repeat these basics: swap the boost sensor with a known‑good one, inspect/replace the intercooler hose, verify vacuum supply and the turbo control valve, clean variable‑geometry linkage, and continuity‑test the sensor wiring and connector. Document results after each step. [Elektroda, solek_87, post #16770751]
Could a parking heater (Webasto) trigger P0105 and limp mode?
Yes. One owner’s P0105 and power loss began after repeated Webasto start attempts. After the heater nearly started successfully, the engine returned to normal and the errors cleared. Pulling the heater fuse is a quick isolation test. [Elektroda, Fokus1981, post #17029983]
What if my Vito doesn’t have Webasto—should I still chase that?
No. If the vehicle lacks a parking heater, skip heater‑related tests and focus on the boost sensor circuit, vacuum, and turbo hardware. The original poster confirmed no Webasto was fitted, making that path irrelevant in their case. [Elektroda, solek_87, post #17032682]
Can turbocharger geometry cause P0105 and low power?
Yes. A blocked variable‑geometry assembly can miscontrol boost and set P0105. One fix involved refurbishing the turbo and replacing pressure sensors, after which power and operation returned to normal. “Now everything works as it should.” [Elektroda, tomas0507, post #18669429]
How do I test the MAP sensor wiring correctly?
Test the three MAP wires in parallel end‑to‑end for continuity and load, not just open‑circuit checks. Also verify wiring to the turbo control valve. This finds hidden resistance or breaks that upset sensor voltage. [Elektroda, jurekk55, post #16771149]
Could a jump‑start or cable start precede this fault?
Yes. One case noted symptoms starting about 30 minutes after a cable start attempt. That timing hints at stress to electronics or wiring, so inspect connectors and grounds before condemning the ECU. [Elektroda, solek_87, post #17026126]
Is using aftermarket boost sensors risky on the W639?
Yes. Owners warn that replacements often read wrong. “It must be original.” Poor readings can keep the van in limp mode and waste diagnostic time. Use an OEM or proven OE‑quality unit. [Elektroda, diodabg, post #17026105]
What 3-step road test can isolate sensor vs. turbo control?
- Log requested vs. actual boost during a third‑gear pull.
- Inspect vacuum lines and confirm the turbo control valve actuates.
- Wiggle‑test harnesses to the sensor and valve while monitoring data.
If data drops or spikes, fix wiring first. [Elektroda, diodabg, post #17026138]
What if swapping sensors and hoses didn’t help?
Escalate to actuator and turbo checks. Clean or refurbish the variable‑geometry mechanism and verify the actuator stroke. One success followed turbo refurbishment plus new sensors, restoring full performance. [Elektroda, tomas0507, post #18669429]
Which real-world fixes actually resolved P0105 in this thread?
Two outcomes: 1) Turbo geometry refurbishment with sensor renewal fixed the fault. 2) Webasto issue cleared, removing the high‑voltage P0105 and restoring power. Both were durable solutions afterward. [Elektroda, tomas0507, post #18669429]
