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Topic Review (Newest First)
03-24-2013 06:06 PM
Back from the dead...


**I take zero personal liability for the information contained herein.
**For all inclusive liability issues... I will not pointedly describe certain specifics, but more to the point, instead give you a direction of thought on what *may* need to be considered for one to get this to work.
**I will also advise one to purchase factory 'Workshop and Wiring Diagrams' from HELM Publications (on CD/DVD.)

Now... with that out of the way. Here is the the basic operational logic behind the Electronic Stability Control (ESC) and what happens:

The Anti-Lock Brake System (ABS) module continuously monitors the vehicle motion relative to the intended course. This is done by using sensors to compare the steering wheel input and the yaw rate sensor input with that of the actual vehicle motion. The Steering Angle Sensor Module (SASM) sends the steering wheel angle and rate of change information to the Anti-Lock Brake System (ABS) module over the High Speed Controller Area Network (HS-CAN) while the Restraints Control Module (RCM) sends yaw rate sensor information to the Anti-Lock Brake System (ABS) module over a private High Speed Controller Area Network (HS-CAN). If the Anti-Lock Brake System (ABS) module determines from the inputs that the vehicle is unable to travel in the intended direction, the Anti-Lock Brake System (ABS) module modulates brake pressure to the appropriate brake caliper(s) and/or wheel cylinder(s) by opening and closing the appropriate solenoid valves inside the Hydraulic Control Unit (HCU) while the hydraulic pump motor is activated. At the same time the Anti-Lock Brake System (ABS) module calculates how much engine torque reduction is required to reduce vehicle speed to help stabilize the vehicle and sends this torque reduction message to the Powertrain Control Module (PCM) over the High Speed Controller Area Network (HS-CAN). The Anti-Lock Brake System (ABS) module also sends a traction event message to the Instrument Panel Cluster (IPC) over the High Speed Controller Area Network (HS-CAN). When the Powertrain Control Module (PCM) receives the torque reduction message, it adjusts engine timing and decreases fuel injector pulses to reduce the engine torque to the requested level. When the Instrument Panel Cluster (IPC) receives this message (gatewayed through the Body Control Module (BCM) over the Medium Speed Controller Area Network (MS-CAN)), it flashes the stability/ traction control indicator (sliding car icon). Once the vehicle instability has been corrected, the Anti-Lock Brake System (ABS) module returns the solenoid valves in the Hydraulic Control Unit (HCU) to their normal position, deactivates the hydraulic pump motor and stops sending the traction event and torque reduction messages. The Powertrain Control Module (PCM) returns engine timing and fuel injectors to normal operation and the Instrument Panel Cluster (IPC) extinguishes the sliding car icon.

The Electronic Stability Control (ESC) function does not operate with the transmission in REVERSE. The Anti-Lock Brake System (ABS) module disables the Electronic Stability Control (ESC) function if there are any wheel speed sensor, stability sensor or steering angle sensor Diagnostic Trouble Codes (DTCs) present in the Anti-Lock Brake System (ABS) module. Also, if there is a communication error between the Anti-Lock Brake System (ABS) module and the Steering Angle Sensor Module (SASM) or the Restraints Control Module (RCM), the Electronic Stability Control (ESC) function is disabled. When the Electronic Stability Control (ESC) function is disabled, the Anti-Lock Brake System (ABS) module sends a message to the Body Control Module (BCM) which gateways the message to the Instrument Panel Cluster (IPC) over the Medium Speed Controller Area Network (MS-CAN) to illuminate the stability/traction control indicator (sliding car icon).

So... what I believe is that one of three interrupts needs to occur:
  • 1. An interrupt to the Electronic Steering Sensor Module (SASM)
  • 2. An interrupt to the Lateral/Longitudinal rate sensors within the Restraints Control Module (RCM)
  • 3. An interrupt to the Yaw rate sensor within the Restraints Control Module (RCM)

Notice that I left off any mention of any kind of interrupt to any Wheel Speed Sensor (WSS.) An interrupt to any WSS will hard fault (and set a DTC code) within the ABS... so, since that isn't a direction that we are interested in... faulting any WSS isn't going to be a player in this.

When reading the logic of the individual systems description and their subsequent operation the three listed interruptions will not disable the Anti-lock Braking System (ABS) nor will effect Dynamic Proportioning through the Electronic Brake Distribution (EBD.) However, I also believe that it may in some way influence operations of associated systems... but likely not hard fault an "ABS" trigger (set a DTC code/red fault indication) within the the Instrument Panel Cluster (IPC.)

The idea is to only interrupt as little as possible without effecting other systems, or... inducing an unsafe operation as an effect from deliberate interruption.

At most any of this will likely introduce a soft fault and possibly set codes in the range of "C0061:xx to C0063:xx"... which can be reset with a scan tool upon fault removal and completing "Diagnostic Routine W."

Another though... would be to install the factory "ST" switch into the car. Here is why that might be a player:
The F-150 owners had issues with the locking differential and stability control, very much like the Focus have now... and by replacing the BCM with that of one from its brother, the Raptor... it worked just the same for the non-Raptor F-150's and they gained control of the locking differential and the ability to shut off the ESC.

Like the F-150... the wiring is already there. However, with the Focus... what is unknown or untested is whether or not the programming is there to support it.

An interesting subject to kick around though...
03-25-2012 02:41 PM
Originally Posted by 1turbofocus View Post
There should be access to some of that in the tuning software but to what degree I wont know till SCT get working tuning software for the 2012 Focus

Thank you Tom. I suspect that, for example, an attempted gearing change for the MTX75 (to the Euro 4th and 5th gears) would be supported by SCT... I hope the TCS-off and ESC-off function is supported, as well.

What about simply a(n electronic / voltage) spike-free simultaneneous cut-off of the (four?) wires leading to / from the angular motion accelerometer, that controls the ESC system along with the steering angle sensor? Surely there would be no need for the ABS logic module to simulaneously kill-off ABS, TCS and ESC, just 'cause one of the two main inputs for ESC has been deactivated? That way, at least ABS could remain active.... Now, I expect that the angular accelerometer (and indeed, most sensors) is CAN BUS.... so it's not like you can exactly modify a resistance, or cut-off a signal, as I understand it.

Come to think of it, though, TCS shutoff is important, too, as between ESC and TCS - the chassis tuning is really impacted.

Thx, in any case. Any others with ideas?
03-25-2012 12:25 AM
1turbofocus There should be access to some of that in the tuning software but to what degree I wont know till SCT get working tuning software for the 2012 Focus

03-24-2012 09:49 PM
ECU Modification Question

In a certain sense, the following should go into the Wheels, Tires, Brakes, etc. discussion forum -- but I really suspect it's only the ECU / Logic Module modifications fellows who'd know how to answer... So please humour me!
Re the 2012 Focus... with ESC and TCS integral with the car: I want to reduce understeer by adding more rear roll stiffness... but I strongly suspect it'd be counteracted by the ESC. I want to make ESC and TCS switchable-off, for Drivers Ed days, or for quick-action-off, in extremely low traction situations where non-switchable (or not QUICKLY switchable) TCS Off is a safety issue.

I have learned that I can (temporarily) disable the three systems -- ESC, TCS, and ABS (but keep the electronic brake force distribution intact.... i.e. the rear wheel brake proportioning) if I cause just the ABS logic module to fault. That means that I would turn the car, on a switched-in and switched-off basis -- to a car without ABS, TCS or ESC... but with proper rear wheel brake proportioning. I suspect that this would be OK, for the ocasional DE day / track event. Incidentally, I should mention that to selectively switch-off TCS, or ESC (individually) and obviously keeping ABS fully intact all the while, is apparently a major ABS ECU programming hurdle.... that few if any folks would be able to accomplish. That's why I talk about simultaneous loss of ABS, ESC, and TCS.

The four individual wheel ABS sensors / tone rings have to remain operable, and the two (?) Hydraulic Control Unit (HCU) solenoids have to remain functional. But the ABS logic module has to fault.

I suspect that I could have the Printed Circuit Board (if this is easily accessible?) modified, so that I can introduce a break in one or several printed circuit tracks...and lead that same break... out of the unit in the form of insulated wires, to a switch (that is made electronically clean, using some kind of voltage spike quelling circuitry... a capacitor or??).

This would constitute a systems on or systems off switch.

Then, I could add-in the amount of front versus back roll stiffness that I desired... and thusly could tune the suspension... without the ESC system intervening. Remember, if the ESC intervenes, it can leave you with a momentary loss of power...

As well, the TCS would be my right foot... not the electronic nanny.

Ideas, anybody? ... but please, please ABS zealots need not preach on the ills of not having ABS under these circumstances... What did people do before ABS was invented? Would those strong ABS advocates NOT buy a classic car (without ABS)? I, for one, would never buy a new or newish car without ABS... but as for TCS and ESC that is not cancellable... I have a problem!
Many thx for any / all who answer!

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