Technical P0657 error with limp mode

[unfacedman]

Hi folks!

All of a sudden, my car started randomly enter into a limp mode (no acceleration) and the only error code given through the OBD is P0657. Nothing more at all.
It happens as i said randomly. Sometimes i delete the error and the car drives normally - until the next time. Sometimes no error delete helps at all - the starting comes along with this error and no acceleration.
I even tried to disconnect the battery for a night - in vain.
Could it be faulty MAP sensor or should I check something else?

 

[koalar]

Black fuse box next to the battery

Check for water damage

Check the relays

Some of the relays are identical so you can swap two over and retest

 

[DaveMcT]

https://www.obd-codes.com/p0657
0657 (Actuator Supply Voltage A Circuit/Open)

It's hard to know what actuator it's connected with but open circuit means a fuse or relay are likely causes. Do you have an automatic gearbox?

 

[koalar]

P06xx = output from body computer

“A” refers to the CAN network I believe

could be anything but seeing as it’s been the main body relay on other Fiat cars (puntos mainly) that’s why I suggested trying the relays in fuse box by the battery first

 

[unfacedman]

https://www.obd-codes.com/p0657
0657 (Actuator Supply Voltage A Circuit/Open)

It's hard to know what actuator it's connected with but open circuit means a fuse or relay are likely causes. Do you have an automatic gearbox?

A manual transmission.
Where can i find which relay is the main? This particular panda is from 2011's harvest.

 

[koalar]

A manual transmission.
Where can i find which relay is the main? This particular panda is from 2011's harvest.

Swap A with B would be my first step

Black box under the bonnet/hood/lid

 

[unfacedman]

Thanks for your reply.
Mine looks different. Here is.
As much as I know, the big black relay actuates the cooling system fan. What do the rest and which one should I check?

 

[koalar]

Thanks for your reply.
Mine looks different. Here is.
As much as I know, the big black relay actuates the cooling system fan. What do the rest and which one should I check?

Look on the inside of the black lid

It’s printed on the inside

If you have the owner manual there’s a description of each one

 

[koalar]

I would start here

But it’s easy enough to swap two the same over at a time until they have all been done except one

 

[unfacedman]

Well, i tried to swap the main relay with almost every possible other one - in vain.
I delete the error code, and when i start the engine - sometimes the error and limp mode comes along immediately, and sometimes - it allows me to rev up as much as I want - on idle. When I put on the 1-st gear and try to move - BEEP! "NO HILL-STOP", "ASR IS OFF" and of course - no acceleration.
Also I've noticed that when the error occures - the throttle position (measured by the TORQUE Android app) shifts from 12.9 to 13.3. But perhaps it is a "feature" of the limp mode...

 

[koalar]

Well, i tried to swap the main relay with almost every possible other one - in vain.
I delete the error code, and when i start the engine - sometimes the error and limp mode comes along immediately, and sometimes - it allows me to rev up as much as I want - on idle. When I put on the 1-st gear and try to move - BEEP! "NO HILL-STOP", "ASR IS OFF" and of course - no acceleration.
Also I've noticed that when the error occures - the throttle position (measured by the TORQUE Android app) shifts from 12.9 to 13.3. But perhaps it is a "feature" of the limp mode...

Fairly common fault for the hill and ASR warning

Doesn’t normally give a running problem though

 

[koalar]

@unfacedman
Any update.

 

[unfacedman]

Well, i forgot to mention that thing happened just after i popped out all the fuses beside the battery looking after a burned out one.
So after that relay swapping didn't help, i replaced the 3 engine management fuses with new ones, though the old fuses were not burned out.
Since then, the problem hasn't occurred yet.
It turns out, that there is some dirt, corrosion or something like that on their contacts.
I've measured the resistance of the old fuses and it was definitely not what's supposed to be (0+-, on new fuse), and it was unstable. Switched and jumped every moment.
So perhaps this was the problem. The unstable current just drove crazy the ECU...

 

[koalar]

Thanks for the update. It could potentially help someone with similar problems

 

[DaveMcT]

I has a strange fault on the 100HP after it sat for weeks during the 2020 Coof lockdown. It switched on fine but refused to start. All the usual checks (fuel etc) proved negative, then while trying MES, found the OBD socket was dead (zero volts and MES could not see the car). I pulled every fuse in the car and tested them all with battery and buzzer. All came out ok. I tested every relay with 9 volt PP3 battery. They all switched just fine. I put them back and the car refused to start. Before going in for dinner, I swapped the headlight and body computer relays.

An hour later, the car started just fine. I never confirmed the cause, but suspect the BC relay was not switching. It's been fine ever since.