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Discussion Starter #1 (Edited)
This is Giulietta 1.4 170hp. Experiencing a sudden loss of power while driving, rpm does not go over 1500, three warning msgs cycle: steering corrector not available, vdc not available, hill holder not available. Additional warning for dynamic and all weather modes not being available if failure happened when driving in dynamic mode. After stopping and starting the engine (need to wait 10s before starting again) the issues clear. Happened at least 10 times.

There are 7 diagnostic codes in total, but C1221 in abs and steering modules could be key, as based on the data recorded in abs module while it happened, it seems to have been recorded first, not sure it means it is initial. The diagnostic software describes it as "Engine ECM invalid signal" and directs to check that the engine ECU has power, and next to check the connection between Engine ECU and ABS ECU. What happens if Engine ECU loses power? Is that even possible for the engine to continue operation?

The remaining codes include DTCs about steering sensors: steering angle and power steering momentum; in addition to body module errors: B1039, B10AA, U1733. Only module that does not have DTCs is the Engine module.

Has anyone had a similar problem? Given the various and seemingly unrelated errors, someone said a weak battery could be a problem. I don't understand how that would be. The battery does not show any sign of a poor condition other than stop&start system not stopping the engine. However, starting the engine is not a problem and afaik this is the most demanding task for the battery. Besides, while driving the car uses the alternator and starting the engine immediately after the failure is not a problem. The parameters recorded during the failure show 14.21V at the time of failure. I checked the battery with a multimeter a few times, it shows ~12.6V while the car is off, and ~14.2V with the engine idling and air con and everything else drawing significant current I could think of on.

This is a car built in 2011. I have had it for two months and it started to have this problem a weak ago. Onset of problems coincided with the weather going from summer to autumn temperatures.
 

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I had the exact same issue with my old 1.4 170bhp and as you say it cleared itself. I left it for a few weeks and turned out it was the multiair unit had failed and spit itself out into the engine causing massive damage and I had to replace the engine. If I were you I’d get the multiair unit checked out ASAP


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Discussion Starter #4 (Edited)
I had the exact same issue with my old 1.4 170bhp and as you say it cleared itself. I left it for a few weeks and turned out it was the multiair unit had failed and spit itself out into the engine causing massive damage and I had to replace the engine. If I were you I’d get the multiair unit checked out ASAP
Sound scary. How does one check for that failure? I thought the MultiAir failure sign is the rough idle - I don't have it. Also, what does it mean for MultiAir to spit itself out into the engine? I read about worn threads; debris getting into cylinder?

Did you see similiar DTCs?
 

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Discussion Starter #5
Sounds like a failing battery to me. It's a very common problem at the age of your car.
I could change the battery but the one I have is not yet two years old and it seems fine. How do I tell it is the battery? Why would the car go into limp mode because of the battery while logging 14.23V and start fine the next minute?
 

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Sound scary. How does one check for that failure? I thought the MultiAir failure sign is the rough idle - I don't have it. Also, what does it mean for MultiAir to spit itself out into the engine? I read about worn threads; debris getting into cylinder?

Did you see similiar DTCs?


I think the only way really would be to get it in an Alfa specialist and have them take it off and look at it. Yeah I had that about a week before the engine failed the rough idle but I also had these problems a few weeks before with the messages popping up on my dashboard. Could’ve been completely unrelated but you never know. From what I could understand about the multi air unit there are nuts inside the unit that vibrate themselves loose, which causes the rough idle and eventually misfiring cylinders, however what mine had managed to do was completely lose the nut which then fell into the driveshaft of the engine and did a lot of damage..


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I could change the battery but the one I have is not yet two years old and it seems fine. How do I tell it is the battery? Why would the car go into limp mode because of the battery while logging 14.23V and start fine the next minute?
If your battery is only 2 years old then this may not be the issue.

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Discussion Starter #8
Putting in a new battery did not help. There is a dtc in electric steering module I did not mention before: C1201 battery error, circuit open. It was there before replacing the battery but I assumed it was me disconnecting the battery with engine off, but MES says the error was recorded at 50km/h. Oddly enough it also says the voltage was 12.8V.
 

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Discussion Starter #9
I was able to record the failure with mes connected to the engine module. It shows throttle angle at 6.38 degrees constant with onset on failure and until turning off the engine. Gas pedal position is changing, but having no effect on throttle. Earlier I assumed there was a reaction, but now I think the rpm just keeps falling because of the narrow throttle opening regardless of what happens to gas pedal. Another thing is that on failure the multiair actuation mode goes to Full-lift and stays there until I turn off the engine.
 

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Discussion Starter #10
I think the only way really would be to get it in an Alfa specialist and have them take it off and look at it. Yeah I had that about a week before the engine failed the rough idle but I also had these problems a few weeks before with the messages popping up on my dashboard. Could’ve been completely unrelated but you never know. From what I could understand about the multi air unit there are nuts inside the unit that vibrate themselves loose, which causes the rough idle and eventually misfiring cylinders, however what mine had managed to do was completely lose the nut which then fell into the driveshaft of the engine and did a lot of damage..


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I had the car at an alfa specialist's, he checked the car but could not conclude what the problem is. He said it might be multiair module, but he was considering replacing it, not looking inside it. I don't know what to think about multi air failure causing unrelated errors in every module except for the engine module. It does not calculate for me. I gather you did not check the DTCs then?
 

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Discussion Starter #12 (Edited)
Faulty throttle body and something wrong with the ecu that it was not showing a DTC for it. Actually, the ECU was not showing any DTCs whatsoever. You can test it it by disconnecting any sensor, like the boost sensor or the map sensor - ECU should have an active DTC before you even start the engine.

The ECU issue was fixed at a dealership, but they could not explain how they fixed it or what was broken. The only thing they did was to update the ABS module software. However, after that procedure the DTCs were showing up as normal, which allowed to diagnose the throttle body.

I was playing with some iPhone DTC odb scanners before that problem, and I wonder if any of that caused the ECU to not display DTCs.

What is sad about all of it is: 1) ECU can get into a state where it is blocking DTCs, not showing any DTC despite entering into a limp mode, 2) unrelated modules throw spurious DTCs that throw you off-track in diagnosis.
 
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