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Discussion Starter · #1 ·
Hi,

It first happened a month ago, I was driving (5 minutes from engine on) in the city and suddenly those lights/warnings went off (ASR/VDC/Steering corrector/Hill holder not available) also the throttle pedal didn't work - the engine start idleing at 1100 rpm and pressing the pedal made the engine go down to ~900 rpm, steering was 100% OK.

After it happened I pulled the car to the sidewalk, turned off the engine, turned it on again and got "Start/Stop not working" and Check engine light but the car was working perfectly.

Since then it happens at least once or twice a day, usually at the very start of the drive or at the very beginning (5 minutes tops).

I tried the following:
1. Replaced the battery with a brand new BOSCH battery (Start/Stop)

2. Went to the central dealer of alfa in my country and ask them to check the car, they said they been over and reinforced all electrical connections and replaced the fuses.
They said they couldn't find anything and said there are 2 things that are left but probably won't cause this problem:
  • the left distribution motor of the climate control system is not working, I believe that I always (2nd hand car) had this problem (indicated by blinking temperature) and it never caused any problem.
  • I have a custom radio that I have built, I had the system installed for a year without problems (only had to change a fuse) and now I took it off just to rule it out.
Needless to say this didn't fixed the problem.

3. Tried to find a pattern for the problem - for now I ruled out the radio system, the AC (both were off and still got the same problem) and it always happens at the beginning of the trip (up to 5 minutes) and it will be more likely to happen if the car was off for a long period.
4. Took information about the faults using AlfaOBD, faults detected (all are intermittent except the climate control one):
  • (ABS) C1221 - Engine Control (NCM) Signal not valid.
  • (ABS) C0074 - Torque requested on steering wheel from CAN (module DST) Signal not valid.
  • (Engine) P1120 - Throttle valve position control Plausibility.
  • (Steering) C100B - Torque limitation request from NFR CAN data not valid.
  • (Steering) C100C - Torque requested on steering wheel from CAN CAN data not valid.
  • (Body computer) B1047 - LIN serial line
  • (Body computer) B1067 - Dynamic control selector on CAN.
  • (Climate control) B1901 - Left distribution motor feedback, Open circuit/Short circuit to + battery.

Logs from AlfaOBD and pictures of the warning lights:

Since I don't really trust the dealers here (they are not professional in my opinion and couldn't help me) I decided to ask here if someone can help me better diagnose this problems
I know similar posts exists but I couldn't find a definitive answer.
 

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On the off chance, did you measure the alternator output? It may have a weak output (ie, failing alternator) which can give you a host of electrical errors
 

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Discussion Starter · #3 ·
The dealer claimed that the alternator is not the problem, how do I check it myself?

Connecting a voltmeter to the battery while engine is running at idle is not the correct check right?
 

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Ive seen it done once when my alternator failed by the AA guy (car rescue mechanic)...and at the time I didnt pay too much attention as the only thing that was in my mind was the car wont start...
I am pretty sure the volt meter / multimeter connects to the alternator and a ground point on the car.

A normal / good alternator should produce around 14V :)
A youtube channel called "Chrisfix" is pretty good
 

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Discussion Starter · #5 ·
So it seems the problem was in the throttle sensor/valve.

The relevant error was: "P1120 - Throttle valve position control Plausibility." and the fact that when the issue happened pressing on the pedal would lower the RPM(!).

Solution: clean the throttle housing - it was a mess there :) no issue over the last week :)
 

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Thank you for this...
The last three weeks the car wasnt nice to drive.. 1km from home it gave an error, it was in basic mode to the office. 5km from the office on the return journey again.
The idling issue in your msg got my attention. Idling at 1100 and slowly dropping.
The weekend I tested the alternator & battery. On Sunday I removed it for the day to determine if it holds charge.

Sunday it went back in the car.. not error whatsoever, none and I drove it for 2hours.

Coming Saturday, throttle body cleanup!!!!
 

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I have a similar problem, intending to replace the throttle body. I can't imagine how a throttle body clean would make a difference here, at least for my throttle body. Now that some time has passed, did it indeed fix the problem?
 

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Alfa Mito, 2010, 1.4NA, 6-speed
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When we had those error messages power steering motor was on way out.
 

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Hi guys, im curious, did someone solved that issue with throttle body/housing and all the problems (limp mode, ABS,VDC unavailable etc.)? ?
 

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So it seems the problem was in the throttle sensor/valve.

The relevant error was: "P1120 - Throttle valve position control Plausibility." and the fact that when the issue happened pressing on the pedal would lower the RPM(!).

Solution: clean the throttle housing - it was a mess there :) no issue over the last week :)
How did you clean it?
 
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