Technical Fiat Panda 1.2 2004 - Rough start and P0351 error code

[rafpanda]

Hey guys, once again I come in search of your expertise.

Some time ago when I started my car the engine light turned on in the dashboard and the car started shaking while the engine was running rough. It stayed like that for a couple of seconds and then started running normally.

Next time I started it everything was fine but it started happening randomly. Now every time I start it it's almost guaranteed it will happen and it doesn't start running normally like the first time, I may have to turn it on and off several times to be able to drive.

Not long ago I replaced spark plugs, cables and coils and the car was running smoothly so this threw me off. My car has the Magnetti Marelli IAW5AF.SP ECU which is usually in the 1.1 I believe and may have a problematic wiring loom, may this be my problem? I attached a pic of the ECU in the engine bay.

I also have to change the torque sensor which I just ordered, I wonder if it's worth it to keep fixing this car although I really like it.

-edit

Forgot to mention: I cleaned the plugs and sockets for the ECU and the coils, nothing changed.

 

[rmjbn1]

P0351 and symptoms are the same before and after changing plugs coils and leads
Is that right?

I would unplug one coil
If symptoms stay the same, that's the coil sending no spark to the plugs
If one coil is sending no spark and you unplug the working one, the engine won't start

Then I would swap the coils over, see if code changes to P0352
That would then confirm coils are working, problem is somewhere before the coil

 

[rafpanda]

P0351 and symptoms are the same before and after changing plugs coils and leads
Is that right?

I would unplug one coil
If symptoms stay the same, that's the coil sending no spark to the plugs
If one coil is sending no spark and you unplug the working one, the engine won't start

Then I would swap the coils over, see if code changes to P0352
That would then confirm coils are working, problem is somewhere before the coil

No, when I changed the plugs, coils and leads the car was running perfectly, that was one year ago and I don't drive the car most of the year.

I will swap the coils to see the result.

 

[koalar]

P0351/2 aren't that common on the Panda,

You can check for spark at each plug

And see if the spark ijumos the same.distance

This is my a 1.2 euro 5 engine yours will have the two coils on the side but the principle is the same

Some more information here

Koalar random thoughts | FIAT Panda (Mk3)

You can tell if the coil pack is getting a control signal and giving a good spark like this If one is weeker and the spark does not jump as far than the others it's suspect It is possible to get a jolt if you do something wrong, probably not a good idea if you have a pace maker As long as the...

www.fiatforum.com

You can also look at the charge times in miltiecuscan, all 4 cylinders should be the same

@rmjbn1 swapping parts and seeing if the fault moves is sensible

On coil does 1 and 4
The other 2 and 3

Swapping part between 1and 2, 3 and 4

HT and plugs

If you change thing one at a time, if the code alters you know which part it was

 

[koalar]

I also have to change the torque sensor

Now every time I start it it's almost guaranteed it will happen and it doesn't start running normally like the first time, I may have to turn it on and off several times to be able to drive.

Rereading

Some alarm bells are ringing

Why is the torque sensor being replaced

Torque sensor faults are quite specific, vibration at the steering wheel, more assistance in one direction than the other, only failing at full lock in one direction

Pretty much every other fault, randomly switching off, worse in winter, worse at the start of a journey and so on are nearly always a power or ground issue
Cables
Alternator or belt
Battery


I may have to turn it on and off several, sounds like an electrical problem
Cables
Alternator or belt
Battery

There appears to be some overlap, it could be coincidence


Maybe start with a block ground test, would be a sensible first move

Koalar random thoughts | FIAT Panda (Mk3)

Hi koaler success someone had insulated the small thread that fits inside the battery tray with tape presumably to stop it rusting I took the tape off so I could get the bolt off then the gauge instantly went to 3/4 so thanks for your help

www.fiatforum.com

 

[rafpanda]

Rereading

Some alarm bells are ringing

Why is the torque sensor being replaced

Torque sensor faults are quite specific, vibration at the steering wheel, more assistance in one direction than the other, only failing at full lock in one direction

Pretty much every other fault, randomly switching off, worse in winter, worse at the start of a journey and so on are nearly always a power or ground issue
Cables
Alternator or belt
Battery


I may have to turn it on and off several, sounds like an electrical problem
Cables
Alternator or belt
Battery

There appears to be some overlap, it could be coincidence


Maybe start with a block ground test, would be a sensible first move

Koalar random thoughts | FIAT Panda (Mk3)

Hi koaler success someone had insulated the small thread that fits inside the battery tray with tape presumably to stop it rusting I took the tape off so I could get the bolt off then the gauge instantly went to 3/4 so thanks for your help

www.fiatforum.com

My steering wheel does vibrate when centered. I checked the other thread about EPS failure and I think you confirmed I probably needed to replace mine.

The battery has some years and it completely discharged a couple of times so maybe I should change it also, would it be wise to start there. I am waiting for a multimeter and I will test it.

 

[rafpanda]

I noticed this issue does not seem to happen when the weather is warmer... When it is cold and rainy it will start idling roughly.

 

[koalar]

When it's cold and wet and failing

Take the air box off and start it in the dark

Look for any arcing

Over the coils and HT leads , a little glitter, sparkle, type effect is normal, it may or may not do it depending on the the atmospheric conditions

Your looking for lightening type effect

 

[Mike1alike]

My steering wheel does vibrate when centered. I checked the other thread about EPS failure and I think you confirmed I probably needed to replace mine.

The battery has some years and it completely discharged a couple of times so maybe I should change it also, would it be wise to start there. I am waiting for a multimeter and I will test it.

Faults on battery / charging system are bad for the EPS. So before replacing torque sensor, make sure everything is ok with battery and charging system. And pay special attention to main ground cable that goes from battery (-) terminal, connects to chassis next to inner wing and goes further to gearbox. Do voltage load tests, check and clean oxidised contacts.

 

[Mike1alike]

Hey guys, once again I come in search of your expertise.

P0351 means problems on the Coil A/1 circuit, the one that controls spark plugs for cylinders 1 and 4.
Best thing to do is not to run the engine snymore in these conditions.
Usually those errors (P0351 and P0352) appear due to bad coil pack but if engine is run with it they often turn into damaged ECU on the coil packs circuits.
So first thing buy new coil packs, good quality.

 

[rafpanda]

P0351 means problems on the Coil A/1 circuit, the one that controls spark plugs for cylinders 1 and 4.
Best thing to do is not to run the engine snymore in these conditions.
Usually those errors (P0351 and P0352) appear due to bad coil pack but if engine is run with it they often turn into damaged ECU on the coil packs circuits.
So first thing buy new coil packs, good quality.

It has almost new NGK coil packs.

 

[Mike1alike]

If the problem persists and you have the error back, most likely ECU is damaged.

 

[Mike1alike]

It has almost new NGK coil packs.

When?

 

[rafpanda]

When?

Changed them a year ago but didn't use the car most of the time since then.

 

[Mike1alike]

Some time ago when I started my car the engine light turned on in the dashboard and the car started shaking while the engine was running rough. It stayed like that for a couple of seconds and then started running normally.

Changed them a year ago but didn't use the car most of the time since then.

And was that problem appearing first time you started the car or how was it?
Did it run ok after that year or problem straight away?

 

[Mike1alike]

Not long ago I replaced spark plugs, cables and coils and the car was running smoothly so this threw me off.

Was this after the problem started? When did you replace those?

 

[Mike1alike]

The fact it’s worse in cold/damp weather is a big clue. That usually points to an ignition breakdown (coil/leads) rather than ECU.
Before going further, I would strongly suggest what it was already suggested above: swapping the coils and seeing if the P0351 fault moves.
If the fault follows the coil → the coil is the issue (even if it was replaced before).
If it stays on the same channel → then start looking at wiring or ECU driver.
At the moment that step is missing, and it’s key to narrowing it down.

 

[rafpanda]

Was this after the problem started? When did you replace those?

No, I ordered them a year ago but thinking about it they were only changed during the spring or summer of 2025, this first happened in January this year but then it started running smoothly again, the car has pretty much not been used since then and now the issue seems to happen more frequently.

 

[Mike1alike]

You need to check. The fault is one of these 3: either bad coil pack, either bad circuit cable/connections either bad ECU.
Just... there is one very tricky part there. Bad coil pack and bad wiring/circuit means shortcut and ECU is very sensitive to that. Running the engine in those conditions can very soon damage the transistors on ECU driver circuit.

 

[Mike1alike]

ECU can be tested without running the engine. Fact that error is intermittent makes it a bit tricky, but usually error appears for sure when ECU is heated. So you can measure it cold that heat it and mesure again.
I'll give you what I have about it from when I had this problem on my Punto. I had the same error P0351, ECU driver was toasted on mine and fix was buying another ECU. I bought a SH one, exactly the same model as mine, virginised. Was plug and play. I hooked it up and engine run well, still does. That was about 4 years ago.
Cross-check the layout on your ECU and find those coil driver circuit pins to do the measuring. Should be about thd same as on Punto.