FAQ
TL;DR: ABS U0401 with traction/power loss on S‑Max 2.0 TDCi? Use a 3‑step check; log engine DTCs during the event. "The error will only be visible when this problem occurs." Root cause often is sticking turbo VGT; cleaning restored performance and stopped U0401 persisting in ABS logs. [Elektroda, bucek21, post #18561321]
Why it matters: This FAQ helps Ford S‑Max/Mondeo/Kuga TDCi owners and techs quickly pinpoint U0401 causes and fix traction/power loss.
Quick Facts
- U0401 in ABS = invalid data from ECM/TCM; may log as “Discontinuous.” [Elektroda, bucek21, post #17456383]
- Traction lamp + limp mode can clear on restart; ABS keeps U0401 while engine DTC vanishes. [Elektroda, bucek21, post #18561321]
- P2263 reported with U0401; limp mode limited speed to approx. 30 km/h in Mondeo MK4. [Elektroda, wri0rex, post #20455287]
- Cleaning variable‑geometry turbo vanes (VGT), incl. ultrasonic, solved U0401/traction issues. [Elektroda, bucek21, post #18561321]
- Ford IDS “Controller Reprogramming” with a Calibration File restores factory ECU behavior and DTC tables. [Elektroda, MobilTruck, post #18750881]
What does ABS code U0401 mean on a 2009 Ford S‑Max 2.0 TDCi?
U0401 means the ABS received invalid data from the engine or transmission controller. In the scan tool, it may appear as “Incorrect data received from engine/transmission control module,” sometimes tagged as a discontinuous event. It points you back to the powertrain as the origin. [Elektroda, bucek21, post #17456383]
Why does the traction light come on and the car lose power until I restart?
The engine enters limp mode due to a powertrain fault, so traction lights up. After a restart, traction goes out and power returns, but ABS keeps U0401. "The error will only be visible when this problem occurs." Scan the ECU during the fault to see the true code. [Elektroda, bucek21, post #18561321]
How do I capture the real engine fault if no code shows after a restart?
Connect a scanner immediately when the traction light appears. Do not cycle the ignition before reading codes. This preserves the engine DTC and freeze‑frame so you can diagnose accurately. "Plug in as soon as the light comes on." [Elektroda, decybel91, post #17456489]
Could a stuck turbo variable geometry cause U0401 and limp mode?
Yes. Sticking VGT skews boost control data, which triggers limp mode and U0401 in ABS. Cleaning the turbo’s variable geometry, even via ultrasonic cleaning, restored normal operation and stopped repeat U0401 reports for the owner. [Elektroda, bucek21, post #18561321]
What 3‑step workflow should I follow when U0401 pops up while driving?
- Pull over safely, engine running; don’t switch off.
- Connect a scan tool and read the engine ECU first.
- Save DTCs and data for boost, MAF, and EGR during the event.
This sequence captures the transient engine fault before it clears. [Elektroda, decybel91, post #17456489]
Does U0401 relate to P2263 Turbo/Supercharger System Performance?
Yes. If P2263 sets, the boost system has a control or pressure issue. Expect limp mode and a traction lamp. Inspect the turbo actuator, its sensor, vacuum plumbing, and the boost control valve as applicable. Fixing P2263 typically clears the ABS U0401. [Elektroda, decybel91, post #20456804]
My engine has an electronic turbo actuator (no vacuum ‘pear’). What should I check?
Your turbo uses a driver and stepper motor. Verify actuator operation and wiring, then inspect the VGT for sticking. Electronic control faults or stuck vanes can still cause limp mode and feed invalid data that triggers U0401. [Elektroda, wri0rex, post #20456811]
What does it mean if unplugging the MAF shows no engine DTC?
That behavior suggests someone disabled the ECU’s fault tables, commonly after a DPF/FAP removal. With error tables off, unplugged sensors may not log engine codes, while ABS still records U0401 from invalid data. [Elektroda, Launch78, post #17457712]
How do I re‑enable factory DTC reporting if it was disabled?
Use Ford IDS and the Controller Reprogramming function with the correct Calibration File. This returns the ECU to stock behavior, restoring normal fault detection and logging. "After such a procedure you have the ECU as it left the factory." [Elektroda, MobilTruck, post #18750881]
Can an ECU software update alone fix these U0401/traction symptoms?
Yes, it can. One Ford Kuga case resolved after updating the ECU software. If hardware checks out, consider a calibration update with Ford IDS to correct control logic issues. [Elektroda, fructon, post #17459240]
Is this issue seen beyond S‑Max, like Mondeo or Kuga?
Yes. A Mondeo MK4 1.8 TDCi reported P2263 with U0401, limp mode limiting speed to about 30 km/h, and a traction lamp. Similar driveline logic applies across related TDCi platforms. [Elektroda, wri0rex, post #20455287]
How long did the turbo cleaning fix last for owners?
One owner reports the issue never returned after cleaning the turbo’s variable geometry with an ultrasonic cleaner. That ended the traction/limp episodes and the persistent ABS U0401 logs. [Elektroda, bucek21, post #18561321]
