Technical Error code C1215 results in loss of ABS, hill holder, ESP, cruise control and start-stop

[Zardo]

Hi,

I have error code C1215. The ABS unit is Bosch 8 ESP 2 (fiat number 71754396, built in July 2010, function time 211748 minutes).

When turning the key, some messages appear that ABS, hill holder and ESP are not functional. Nor is cruise control and start-stop.

Using google, I found a page from the official Elearn site citing this error for a Fiat 199 diesel model (only worked for a few pages for this specific model).

I city the information provided:

The diagnostic equipment signals the following error: "C1215 - brake switch"

This error can be signalled in two sets of cases.

The first is when there is an open circuit in the brake lights switch or the wiring, the brake lights are burnt out or the reading circuit is damaged. In these cases the voltage reading at the brake lights switch is not in the range below 55% (pedal released) or above 75% (pedal pressed) of the battery voltage.

The second group of cases is where there is an open circuit or short circuit (at the positive or to earth) of the wiring or the brake lights switch, if the switch or the reading circuit is damaged. In all these cases the braking action is detected without pressing the brake pedal switch (or the closure of the switch contacts)

The voltage should be less than 55% of the battery voltage if the pedal is released - The voltage should be more than 75% of the battery voltage if the pedal is pressed

I had a wiring problem in the past when the left front tyre ate the isolation of the wire of the wheel speed sensor. At the time, the OBD also showed the brake switch error. The wiring problem was repaired, and the brake switch error went away during summer. However, it reappeared once the winter season began last winter and has persisted since. I checked the speed of the wheels and they synchronize correctly.

Most of the time, the error messages appear right after starting the engine, independent if the brake pedal is pressed or not. Sometimes it appears later, the first time the brake pedal is pressed.

So should I first check whether the brake lights function correctly when hitting the brake? If that's the case, check the voltage of the brake switch? Then inspect the wiring harness for damages?

Thanks

 

[the green vanper]

Hello,

Do the brake lights work? If the sensor is damaged, it can cause such errors. So check it first.

 

[Zardo]

Hi,

Hello,

Do the brake lights work? If the sensor is damaged, it can cause such errors. So check it first.

You're totally on point for asking this.

This evening, I checked every exterior light: they all work except for the brake lights.

Pulling the handbrake doesn't power the brake lights.
Pushing the brake pedal doesn't power the brake lights.

The command "brake light check" on AlfaOBD does power both brake lights and their brightness is normal!

In addition to the C1215 error of the Bosch ABS unit, the body computer shows the same fault but calls it "B1010 brake switch error present"

I'll check the brake switch next if I'm able to reach it - I couldn't even see it on this left hand drive Punto Evo, seems the switch is located very high in the foot well and directly behind the pedal support.

Edit: maybe I should check the switch of the handbrake, too. However, the OBD system was able to "see" that the handbrake was pulled and released.

 

[the green vanper]

If the pulled handbrake shows on AlfaOBD it means that it's sensor works perfectly.

If you can activate the brake lights from AlfaOBD but they don't light when you push the brake pedal, the problem would be more likely the brake pedal sensor. Could also be the wiring.

Usually it is very high on the pedal, true

 

[Zardo]

I found some information online for a Fiat 199 1.4 T-jet "applicable to versions with manual gearbox, from 10/2008" which describes the pin layout of the brake switch as follows:

4 pins on that brake switch, from left to right:
Pin 1: cable 0.5 color VB goes to Body computer (front) pin 27
Pin 2: cable 0.35 color VN goes to Body computer (front) pin 34
Pin 3: cable 0.35 color LN goes to Body computer (rear) pin 25
Pin 4: cable 0.5 color LR goes to Body computer (rear) pin 7

ChatGPT:

In Fiat wiring diagrams, the color abbreviations typically represent the color of the wire insulation. Here’s what the abbreviations usually mean:

1. VB (Verde-Bianco): Green with a white stripe.
2. VN (Verde-Nero): Green with a black stripe.
3. LN (Blu-Nero): Blue with a black stripe.
4. LR (Blu-Rosso): Blue with a red stripe.

Now this doesn't seem to be a CAN bus but rather something else, probably just primitive pull-down or up switches ?

Additionnal quote from the Elearn:

The switch fitted on the pedal unit consists of two contacts which supply two signals: the first is N.A. type, which recognises the position of the brake pedal if it is not in the rest position, i.e. the pedal is pressed; the second is N.C. type, which recognises the position of the brake pedal in the rest position.
The lights are switched on by the N.O. contact (pedal pressed).
The control function is activated by the enablement signals (key on MAR-ON) and the command from the contact of the switch.

The brake lights check function monitors that the side lights are working correctly: the following are checked:
- open circuit (bulb missing or wiring interrupted)
- short circuit to earth (bulb s.c. or wiring s.c. to earth)
- short circuit to battery voltage (wiring short circuited to Vbatt)

The continuity of the fuse protecting the switch on the brake pedal is also checked.

When one of the situations described above is verified, the Body Computer makes the failure status available to the CAN: a special lights failure warning light switches on in the instrument panel and, at the same time, the information is shown in the display by means of the specific symbol.

I fed ChatGPT with some of this information, asking it about the Emergency braking functionality (flashing brake lights) and whether the brake switch had a role in it. It appears not so.

Flashing brake lights during emergency braking relies on data that may come from several sources. While the brake switch provides useful information about pedal position and initial activation, the decision to activate emergency flashing brake lights is typically more sophisticated and involves additional inputs.

Brake Switch Contribution​

The brake switch can indicate:

1. Pedal Pressed (N.O. closed): Signals the brake pedal has been activated, which would light the brake lights during normal braking.
2. Pedal Released (N.C. closed): Confirms the pedal is not pressed, resetting the system.
3. Full Pedal Travel: The brake switch's mechanical range could theoretically signal that the pedal has been fully depressed, suggesting a forceful braking action. However, the brake switch alone cannot assess braking force or urgency accurately.

Emergency Braking Detection​

The emergency braking flash function relies on detecting the intensity and speed of braking, which cannot be determined by the brake switch alone. Instead, the system uses the following inputs:

1. ABS Unit (Wheel Speed Sensors):
   • Monitors the deceleration rate of the wheels. A sudden, significant deceleration (indicative of emergency braking) can trigger the flashing lights.
   • Compares speed differences between wheels to detect rapid braking or skidding scenarios.
2. Brake Pressure Sensor (if equipped):
   • Measures the hydraulic pressure in the braking system.
   • High pressure applied suddenly indicates emergency braking, which may supplement or replace brake switch input for triggering the flash.
3. Dynamic Stability Control Logic:
   • If the vehicle is equipped with stability systems like ESC (Electronic Stability Control), these systems can analyze multiple parameters, such as yaw rate, lateral acceleration, and braking force, to decide if emergency braking is occurring.

Role of the Brake Switch in Emergency Braking​

The brake switch is primarily a binary sensor (pressed/not pressed) with some redundancy (N.O. and N.C. circuits). While it:

• Signals that the pedal has been activated,
• Confirms the pedal position is consistent with full depression,

it does not provide force-sensitive or time-sensitive data, which are critical for determining an emergency braking scenario. Instead:

• The ABS unit or stability control system makes the decision based on pressure sensors or deceleration rate, independently of the brake switch.

Summary​

The brake switch contributes to pedal position and engagement status but is not solely responsible for emergency brake light activation. The system primarily relies on:

• Rapid wheel deceleration (ABS sensors).
• Hydraulic pressure readings (if equipped).
• Stability control data.

If you're troubleshooting or modifying the system, it's worth consulting the vehicle's wiring diagrams and ABS module specifications for the exact logic used in emergency braking detection.

 

[the green vanper]

As far as I remember old style primitive brake pedal switches, they had 2 wires only

 

[Zardo]

Three days ago, I replaced the brake switch with a new one, ordered from Fiat.

The numbers of the FIAT Eper for that Abarth model as found here do not correspond with the number of the item provided by Fiat.

EPER:

55501-020

APPARATUS AND ELECTRIC CONTROLS

SIGNALLING DEVICES

50512681​

SWITCH

Fiat provided a part with a different number (they told me they checked the number of my chassis against their catalogue) : it's 52092117 for a price of 38 CHF which is about 40 Euros.

After I received the part from my Fiat dealership, I tried this new number on several online providers of automotive parts. Most sites claimed the part wasn't compatible with my 2010 Abarth Punto Evo multiair 120 KW car. Only 2 sites claimed they had this exact part (albeit not OEM) and that it would fit. There was actually a huge choice of different brake switches, but only one had the exact same colors has my OEM part provided by FIAT (it was half the price, too).

I measured the new part using a digital multimeter, but all of the 4 connectors had infinite resistance (above 20 Mohm). So when doing the repair, I was worried that the new part might not work. But it did! Maybe the part has an internal mechanism which activates the contacts only if the device is in place and turned 45°.

On this left hand drive car, I had to remove the driver's seat (and disconnect the Airbag and the weight sensor of the seat) and the black plastic air diffusor (a single TORX 25 screw), and crawl down under with a headlamp. I turned the switch counterclockwise 45° as viewed from the passenger compartment (turning the upper part towards the left) and disconnected the cable connector with a small piercing awl. I got the new switch and first connected it with the cable. With very limited visual control, I pushed it through the square hole in a 45° counterclock angle (viewed from inside the car) and pushed the switch against it so it got straight and fit the mechanism. I then turned it clockwise 45° (upper part towards the right) to get it vertically aligned. Put the air diffusor back in place. Finally, I put the driver's seat back in and reconnected its airbag and its weight switch. It was quite tedious.

Also, as the driver's seat has an airbag, I did NOT test the brake switch with the driver's seat removed, as this likely would have caused an additional error in the ECU and the airbag unit. So I did not activate ignition during repairs and waited until everything was in place again.

By the way, the probe of the new brake switch is about 1 cm longer than the old one.

Using AlfaOBS, I cleared the fault in the Bosch ABS unit and in the Delphi ECU. After clearing the fault, the fault did not come back. Test drive of 50 km was successfull, too. All the electronic assistants were available again: Cruise control, hill holder, ESP, start-stop, ASR... and the brake lights work, too! What a relief!

---

To gain access, remove the black plastic air diffusor (you see its two big square holes), only held in place by a single 25 TORX screw on the left:

Old brake switch in place (the blue and orange thingy, you can see the mobile black plastic probe and its white tip protruding from the switch, it pushes against a lever frome the brake pedal mechanism:

New brake switch in place:

Number of the new switch:

 

[the green vanper]

Happy it works now Congrats