Technical Fiat 500X 1.4 Multiair (2018) DCT issue

[f1matt23]

Hi,

I recently bought a 1.4 500X with a DCT transmission, which started to behave strangely last month. When slowing down, it doesn't always shift back to D1 from D2. In this case, the car doesn't react to anything, as if it's not in gear. The display doesn't even indicate any gear position (P - R - N - D). After the first time, I took it to a mechanic, there were no error codes, he measured the battery and it was fine. He asked me to use the start stop function. About a week later, the problem appeared again, but now D on the transmission was flashing and beeping, and a text appeared on the small display in front of me to put the transmission in N or P. After that, we got several error codes.

B1041-16 Rfhm Electric Failure 1 - Circuit Voltage Below Threshold
U1930-29 Ignition Working Condition Signal From BCM - Signal Invalid
C1200-1F Electric Power Steering (EPS) System is detecting intermittent voltages out of range.
B106D-86 When the Body Control Module (BCM) detects an invalid signal from the Terrain Switch Bank Module.
U1700-86 Body Control Module (BCM) - (Faulty) invalid signal

I'll probably get to the car electrician this week, he said out of the blue that it would be the battery, but it was replaced yesterday and the problem appeared again.
I'm a little bit disappointed. The car only has 67,000 km (41600 miles).



Has anyone experienced something similar?

 

[s130]

With those codes across multiple systems then I would be suspecting a poor earth / grounding problem.

I gather some people have had issues with the battery ground strap to chassis and engine so this is where I would be looking to start with.

On a side note I've always found it odd that most battery ground straps/connections always seem to be located beneath or very close to the battery where over time corrosion is going to occur even with so called sealed batteries.

 

[silvanu96]

1.4 Multiair with DCT transmission ? 1.3 FireFly is with DCT ...
1.4 Multiair is with ZF9 which is not DCT transmission...

 

[f1matt23]

It's a 6 speed dry dual clutch transmission.

I took the car to Fiat dealer, but there are no fault codes for the transmission, only low voltage codes across multiple system. It seems like they wouldn't even bother with this, they would rather take the transmission apart to see if there is a mechanical problem. That is quite expensive and even then the problem wouldn't be solved, just by looking at the transmission. I don't know what to do.

Is it completely impossible that there is a problem with the shifts due to a voltage problem?

 

[porta]

It's a 6 speed dry dual clutch transmission.

I took the car to Fiat dealer, but there are no fault codes for the transmission, only low voltage codes across multiple system. It seems like they wouldn't even bother with this, they would rather take the transmission apart to see if there is a mechanical problem. That is quite expensive and even then the problem wouldn't be solved, just by looking at the transmission. I don't know what to do.

Is it completely impossible that there is a problem with the shifts due to a voltage problem?

Yes, poor voltage results in poor signals from everything from the RFT, BCM and other modules…they all talk to each other and need good communication voltage to work properly!

 

[s130]

Today's vehicles with all the electronics and inter node communications then the following are essential:

1) Good earthing / grounding between battery and chassis and other ground connections

2) Good battery

3) Good alternator / battery charging

System wide low voltages are NOT good and this needs to be sorted / addressed before anything else.

 

[f1matt23]

Update

There was a bit of a misunderstanding, the dealer only talked about the codes I provided, but when they ran the diagnostics, no fault codes appeared. So probably the fault codes that were cleared after the battery replacement did not appear again (good sign). Since there are no fault codes, they do not recommend that we take the transmission apart or change anything till we know the exact issue, all they did was reset the systems. They asked me to drive it and bring it back if there were any fault codes.

I doubt that this will solve the problem, but we'll see what the future brings. If there is anything to the matter, I'll definitely write about it in case anyone encounters a similar case.

Thank you guys for the comments, really appreciate it (sorry for my bad english)

 

[s130]

Update

There was a bit of a misunderstanding, the dealer only talked about the codes I provided, but when they ran the diagnostics, no fault codes appeared. So probably the fault codes that were cleared after the battery replacement did not appear again (good sign). Since there are no fault codes, they do not recommend that we take the transmission apart or change anything till we know the exact issue, all they did was reset the systems. They asked me to drive it and bring it back if there were any fault codes.

I doubt that this will solve the problem, but we'll see what the future brings. If there is anything to the matter, I'll definitely write about it in case anyone encounters a similar case.

Thank you guys for the comments, really appreciate it (sorry for my bad english)

Thanks for the update. With a bit of luck the nice new fresh battery will solve your problem.

As the battery is new I would: (check and record)

1) Do a voltmeter check with the ignition OFF
2) Do a voltmeter check with the ignition ON
3) Do a voltmeter check with engine ON and at idle RPM
4) Do a voltmeter check with engine ON and at idle 2000 RPM
5) Repeat 3) and 4) with Lights (side & headlamps), cabin fan on full, rear screen heater on

Doing this will give you some benchmark reference values to check against in the future. Easy and quick to do.

No need to say sorry for your bad English. Least you had the courtesy to try and communicate in English AND come back to us with updates / corrections.

Thank you!

 

[f1matt23]

It didn't take long for the problem to reappear, when I put the gear lever in reverse the car started to make small jumps (it was like someone was pushing the car), I stepped on the gas nothing happened, I put it back all the way to P the strange movement stopped immediately and then I successfully engaged R.

Could it be a mechanical problem such as worn clutches?

 

[s130]

I'm no expert or even much knowledge of the DCT automatic boxes but I'm wondering if because you had low voltages the DCT ECU did some form of reset and/or lost it's calibration points. If so the the system needs to re-learn all it's operating parameters.

Also this gearbox totally relies on hydraulic fluid etc. to operate. So air in the system will affect it's operation.

 

[f1matt23]

the dealer said they reset the systems to default, I thought this means calibration I'm gonna call them tomorrow to confirm.
However I did not notice any jerking before. This was very noticeable now. It was as if someone was constantly pushing the car from behind.
Stopped immediately when I put shifter to Park.

 

[s130]

the dealer said they reset the systems to default, I thought this means calibration I'm gonna call them tomorrow to confirm.
However I did not notice any jerking before. This was very noticeable now. It was as if someone was constantly pushing the car from behind.
Stopped immediately when I put shifter to Park.

Jerky and un smooth when driving would in a normal manual gearbox suggest some form of clutch slip and grab. Quit / very rare as normally the clutch bites/works till it can no longer hold the load through plate friction/pressure and then continuously slips till load is removed/reduced.

The DDCT box is in reality a hydraulically controlled manual box with TWO large clutch plates as opposed to the older Automatic Transmissions.

One clutch plate does the ODD gears and the other the EVEN gears. Which gears (odd / even) does the problem occur in or is it both odd and even?

 

[f1matt23]

Yesterday the gear was in D2 I was morving forward very slow and the car started jerking / shaking. At full stop the gear positition indicator were gone and the car kept shaking till I put the gear in P. The engine also had strange sound, it was something like rippling.