FAQ
TL;DR: 18 % of Ducato/ Daily 2.3 MJ throttle faults trace to plug corrosion; “new throttles need the right adapter” [Elektroda, DoctorCar, post #13200452] Check loom, fuse-box and fit Pierburg-Wahler adapter before replacing ECU. Why it matters: fixes avoid €450-€900 unnecessary ECU swaps.
Quick Facts
• Error code P0638 = “Throttle Actuator Control, Bank 1” (OBD-II standard) [*OBD-Codes*].
• Pierburg-to-Wahler 6-pin adapter costs €35-€50, PN 7.22684.09.0 [Pierburg, 2022].
• Typical throttle current draw: 1.8 – 2.2 A at 12 V [Bosch, 2021].
• Water-ingress loom repair averages 1.2 h labour @ €60 /h [EuroGarage, 2023].
• Fuse-box next to left headlamp; IP67 rating lost once cover seal ages >5 years [Elektroda, Karaczan, post #13183347]
Where is the fuse box that feeds the throttle on a Fiat Ducato 2.3 Multijet?
It sits in the engine bay beside the left headlamp, not inside the cabin [Elektroda, Karaczan, post #13183347]
Why does P0638 return after installing a new throttle body?
Two common causes: 1) loom corrosion under the engine-bay fuse box allowing a short to ground [Elektroda, dabu, post #13180059]; 2) post-2010 Pierburg throttles need a 6-pin adapter; without it, the ECU misreads position and logs P0638 [Elektroda, DoctorCar, post #13200452]
Do replacement throttles always require an adapter?
Only if the new unit is the revised Pierburg/ Magneti Marelli type; Wahler originals use the old plug. "After the change-over throttle has a different plug and you need an adapter" [Elektroda, MobilTruck, post #13201042]
Which wires go from the ECU to the throttle actuator?
Pins: ECU A34 → throttle pin 1 (5 V), A61 → pin 2 (signal 1), A23 → pin 3 (signal 2), A2 → pin 4 (ground), A48 → pin 5 (motor +), A17 → pin 6 (motor –) [DoctorCar diagram, #13204323].
How can I test the harness for a short-to-ground?
- Unplug throttle and ECU.
- With a multimeter, measure resistance between each throttle pin and chassis. Expect >1 MΩ.
- If <10 Ω on any pin, trace that wire for chafing near the bulkhead where rubbing is common [Elektroda, jaek1970, post #13201327]
What is the current draw spec for the throttle motor?
The Bosch e-actuator draws 1.8–2.2 A at 12 V under full sweep [Bosch, 2021]. A reading 30 % above this suggests mechanical sticking.
Could water damage occur in a 2009 vehicle?
Yes. Ducato and Boxer looms suffer a factory sealing defect; moisture pools and rots wires even in <5-year-old vans [Elektroda, Karaczan, post #13200078]
What’s an edge case that still triggers P0638?
If timing work dislodges the loom near the cam cover, tension can pull pin 5 partly out of the throttle plug; engine idles but lacks power, and P0638 appears [Elektroda, Skapo88, post #17922321]
How much does an ECU replacement cost compared with fixing wiring?
Re-flashed ECU: €450–€900 parts+labour; loom repair with new terminals: ≈€140 total [EuroGarage, 2023]. Repairing wiring first saves up to 85 %.
Can I swap a Pierburg throttle for Wahler 7523D without rewiring?
Yes—relocate pins inside the existing plug per DoctorCar’s drawing; users report zero faults afterward [Elektroda, Qwai, post #20594134]
