Technical Help Needed: Panda 1.2 Throwing ESP, Airbag & Body Computer Errors (U1602)

[johnypar]

Good morning and greetings from Greece.

I own a Panda 1.2, 8v, EMOTION. The car has been operating without any issues since 2018, when I bought it. Last December, after replacing the clutch kit (I mention this because I’m not sure if it’s related or just a coincidence), the car started showing errors in the ESP and Hill Assist systems, as well as in the power steering. However, the steering itself works normally.

The other systems do not function, and the warning indicators appear on the dashboard. Over the past week, the airbag warning lights have also started to come on, either when I start the car or while driving. However, the issue is not constant — there can be days without any warnings. Most of the time, though, all the warnings appear, roughly 7 out of 10 days.

I also noticed that moisture gets inside the passenger-side headlight. When it dries out, the frequency of the errors decreases significantly. However, in that same headlight, the W5W bulb has burned out — I mention this in case it could be affecting or disturbing the CAN system. Also, inside the headlight, I have noticed that the wiring appears to be significantly deteriorated.

I should also mention that the battery is new and was replaced one month before the problems started. Another observation was that there was heavy corrosion on the negative terminal, so I replaced it with a new one, as the original had become loose over time.
I measured with a multimeter, with the engine off : 12.3–12.5V, and when engine running: 13.9–14V.

In MultiECUScan, I am getting a Body Computer error U1602, which I am unable to clear.

I should also add that twice I have received an ECU error related to the lambda (oxygen) sensor. I saw a video on YouTube suggesting that U1602 could sometimes be a “ghost error,” but with the dashboard lighting up like a Christmas tree, I don’t think this leaves much room for it being just a ghost error.

I apologize for the long post — I’m providing as much information as possible in order to get some help, as at a workshop the likely answer would be to replace the Body Computer… which might be true… or maybe not.

Thank you in advance.

 

[bugsymike]

Re your MES error codes, is it a full version as I would expect more detail regarding the cause of airbag codes etc.
I used a friends Snap On diagnostics and was able to read that the cause was the passenger seat occupancy sensor, unfortunately it had been badly repaired by the previous owner destroying the BCM this was on a 2010 Punto Evo. I was able to fix the issues, but it did involve a new BCM and then use the Snap On again to do a "proxi alignment so the BCM could recognise all the components.
I assume you do not have Stop/Start, but if you do then a specific battery has to be used also there is a sequence for disconnecting the battery to prevent error codes relating to that.
Bad earthing connections can be a cause of many error codes, so well worth checking.

 

[johnypar]

Re your MES error codes, is it a full version as I would expect more detail regarding the cause of airbag codes etc.
I used a friends Snap On diagnostics and was able to read that the cause was the passenger seat occupancy sensor, unfortunately it had been badly repaired by the previous owner destroying the BCM this was on a 2010 Punto Evo. I was able to fix the issues, but it did involve a new BCM and then use the Snap On again to do a "proxi alignment so the BCM could recognise all the components.
I assume you do not have Stop/Start, but if you do then a specific battery has to be used also there is a sequence for disconnecting the battery to prevent error codes relating to that.
Bad earthing connections can be a cause of many error codes, so well worth checking.

I have the full version of MES, but I don’t have the adapter needed to access the airbag and ABS modules. I’m expecting to receive it within the next few days, as I also want to see what faults those units have recorded.

The car does not have Start/Stop; it uses a standard battery, so I have installed a new Bosch S5.

I have checked all the earthing points around the battery and the gearbox (which is located under the battery), as I thought that maybe something was left loose or not reinstalled correctly when the clutch kit was replaced.

 

[koalar]

Let's start at the beginning in multiecuscan

Is U1602 showing

Present/active
Or intermittent

You can clear active codes

The gearbox earth was removed to do the clutch

Test the block ground while cranking

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

With a multimeter on low volts DC it should start at around 0.3 dropping to 0.1

 

[koalar]

If the code isn't active try car scanner to clear the code


U1602 are most common after the battery been removed, changed and should clear, normally nothing to worry about, intermittent

U1602 active is going to cause all sorts of problems though

 

[johnypar]

The RED warning lights are now on.​

​

 

[johnypar]

Let's start at the beginning in multiecuscan

Is U1602 showing

Present/active
Or intermittent

You can clear active codes

The gearbox earth was removed to do the clutch

Test the block ground while cranking

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

With a multimeter on low volts DC it should start at around 0.3 dropping to 0.1

The error is Active and Fatal. However, I am unable to clear it — when I press “Clear,” MultiECUScan removes it momentarily, but within a fraction of a second it reappears in the error list.


I want to perform the test on the engine ground, but could you guide me on what is meant by it dropping from 0.3 to 0.1?

 

[koalar]

Yep follow the link kind of explains it all

Clean a bit of the engine block to shny metal
Clean the top of the battery terminal to shiny metal

Prevent the car from starting, disconnect the fuel injector harness. Ignition harness, remove the fuel pump fuse, there's many ways, not sure if this works on your model but pressing the accelerator pedal to the floor works on some

Put the multimeter on DC volts

Choose a low range, if the meter isn't auto ranging 2V Or 20V what ever your meter has

Put one lead on the block and one lead on the battery nevative

Get someone to crank the car and measure

In an ideal world it would measure 0.0V

But there is always some resistance in the wire, and there will also be a small voltage across the probes

As the starter first gets it power and before the engine start to turn it will be around 0.3V as the engine starts to crank it will drop to around 0.1V

I wouldn't be concerned if it measured 0.3V much above this and it will need addressing before we can move on

 

[koalar]

The error is Active and Fatal. However, I am unable to clear it — when I press “Clear,” MultiECUScan removes it momentarily, but within a fraction of a second it reappears in the error list.

Active can not be cleared

There a network problem between the different modules and the body computer

Is.it the standard radio

Do you have blue and me, if yes does it work

Start with the reference ground above

 

[johnypar]

Yep follow the link kind of explains it all

Clean a bit of the engine block to shny metal
Clean the top of the battery terminal to shiny metal

Prevent the car from starting, disconnect the fuel injector harness. Ignition harness, remove the fuel pump fuse, there's many ways, not sure if this works on your model but pressing the accelerator pedal to the floor works on some

Put the multimeter on DC volts

Choose a low range, if the meter isn't auto ranging 2V Or 20V what ever your meter has

Put one lead on the block and one lead on the battery nevative

Get someone to crank the car and measure

In an ideal world it would measure 0.0V

But there is always some resistance in the wire, and there will also be a small voltage across the probes

As the starter first gets it power and before the engine start to turn it will be around 0.3V as the engine starts to crank it will drop to around 0.1V

I wouldn't be concerned if it measured 0.3V much above this and it will need addressing before we can move on

Thank you for the guidance, I will try this with the cable and get back to you.

To be honest, I believe something wasn’t reassembled correctly after the clutch replacement, as the errors started the very same night.

I don’t have the factory radio or Bluetooth. I have a standard 9-inch Android head unit.

 

[koalar]

Thank you for the guidance, I will try this with the cable and get back to you.

To be honest, I believe something wasn’t reassembled correctly after the clutch replacement, as the errors started the very same night.

I don’t have the factory radio or Bluetooth. I have a standard 9-inch Android head unit.

Is it connected with a canbus adaptor

If so it might be worth temporarily disconnecting it if it is and check if the U1602 will then clear

But lets get the checks above out the way first, it's easier and quicker

We have a few third party adapters cause random problems occasionally over the years

 

[koalar]

Any update

 

[johnypar]

Any update

Unfortunately, I don’t have any updates, as my wife uses the car and I only have enough free time on weekends. So, over the weekend I will look into it further and will keep you informed.

Thank you very much.

 

[johnypar]

Good morning from Greece again....a long message will follow.


I started by checking the wiring with a multimeter… everything seemed fine. I unscrewed and cleaned all the car’s grounding points on the transmission, the chassis, the ECU, everything.


The car then threw the P0130 error again (Lambda signal above the catalytic converter). I noticed that the connectors of both lambda sensors had a bit of oil on them, so I removed and cleaned them to see if that would change anything in the car’s operation (I’ll see if the lambda error comes back in the future).


I reassembled everything… and then again: Hill holder failure, ESP failure, steering failure.


The steering failure disappears as soon as I move the steering wheel. However, something I forgot to mention last time is that I might start the car and it runs without any errors, but as soon as I touch the steering wheel to move out of a parking spot, all the above errors appear, with the difference that the steering wheel does NOT work. I have to turn the car off several times and restart it for the issue to go away.


I disconnected the Android head unit I have...all the errors disappeared! I took the car for a drive… during the trip I turned it off and on again… everything was fine. I thought I had found the culprit. I returned to my parking spot, parked the car… and suddenly, everything came back again. So the screen is not the cause either.


Also, the U1602 error is still there , I can’t clear it through MultiECUScan.


Let me add one more detail that might help: the car was unused for 6 months, and the battery died. After those 6 months, I replaced the battery and put the car back into use.


So I started thinking: could this period of inactivity have affected the steering torque sensor, since the errors seem related to the CAN system that manages it? Does that make sense? Is there anything else that communicates on that specific CAN network and is located around the transmission area? Should I check whether something shifted after the clutch kit replacement?

 

[koalar]

Multimeter on around 20V DC

No load, all electrics off
Load, rear window heater,main beam and, heater blower on full

What the voltage acoss the battery ignition off
1, At idle no load
2, At idle under load
3, At 2.5K rpm under load


Multimeter on millivolts AC

4, At idle no load
5, At 2.5K rpm under load

Take a small video of the dash as the car is started

 

[johnypar]

Multimeter on around 20V DC

No load, all electrics off
Load, rear window heater,main beam and, heater blower on full

What the voltage acoss the battery ignition off
1, At idle no load
2, At idle under load
3, At 2.5K rpm under load


Multimeter on millivolts AC

4, At idle no load
5, At 2.5K rpm under load

Take a small video of the dash as the car is started

What can we conclude from the above tests? Sorry for asking, but I would like to fully understand what I am doing. It is simply my engineering curiosity, and I want to understand all situations clearly.

 

[koalar]

What can we conclude from the above tests? Sorry for asking, but I would like to fully understand what I am doing. It is simply my engineering curiosity, and I want to understand all situations clearly.

Steering sounds power related
We are testing the alternator

 

[johnypar]

Steering sounds power related
We are testing the alternator

I’ll go through them and let you know. Thank you very much for the advice.

 

[koalar]

I’ll check them and get back to you. Thank you very much for the advice.

Worth checking

There's very little gap between the stationy part and rotating parts of the alternator,.if left standing they can corrode together up causing problem or even cracke the case

Probably less than 50% chance but worth ticking off as it's easy to do

 

[johnypar]

Worth checking

There's very little gap between the stationy part and rotating parts of the alternator,.if left standing they can corrode together up causing problem or even cracke the case

Probably less than 50% chance but worth ticking off as it's easy to do

I know I’m getting ahead of things… but assuming everything is fine, what would be the next step? What could be causing it?