# [EVDL] Feeding a fake idle signal to the vehicule computer



## EVDL List (Jul 27, 2007)

What is the make and model of the vehicle?

Barry

-----Original Message-----
From: [email protected] [mailto:[email protected]]On Behalf
Of nicolas drouin
Sent: Wednesday, June 18, 2008 9:04 AM
To: Electric Vehicle Discussion List
Subject: [EVDL] Feeding a fake idle signal to the vehicule computer


Hi,

Does anyone have any leads for feeding a false RPM 'idle' to the
vehicle computer of a modern car? It essentially seems like the tach
input (with a multiplier).

I met someone yesterday who is having trouble with his start-up
sequence because the vehicle computer thinks the engine is off and so
it does not start the OEM electric power steering pump.

What he's tried:
Attaching the OEM sensor to a fan with adequate gearing. He didn't
like the mechanical dependency of this solution.
Creating a 555-chip based circuit to drive a +/-12V pulse; but this
keeps blowing on him.

Alternatives:
Wire the power-steering directly into the 'ON' 12VDC bus?

The controller is a Curtis 1231C. I know the Zilla comes with a tach
output on the hairball, what do people use for a tach when using a
Curtis?

Thanks,

-Nick

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## EVDL List (Jul 27, 2007)

How are you "blowing" the 555? Are you running the 555 output directly into=
the engine computer or are you buffering/redriveing the signal first. Anot=
her thing to note is a lot of engine sensors (varies by car) are driven off=
weird voltages from the computer. If you drive a 12V signal in where they =
expected 8V 4V of that just gets drained to the 8V rail / reg thought the p=
rotection diodes. (and may explain why the 555 is dying). =


If you got a sketch of what your using feel free to send me a copy and I ca=
n see if there is anything easy you can do to harden it some more. =


Later,
Peter

> Date: Wed, 18 Jun 2008 09:03:48 -0400
> From: [email protected]
> To: [email protected]
> Subject: [EVDL] Feeding a fake idle signal to the vehicule computer
> =

> Hi,
> =

> Does anyone have any leads for feeding a false RPM 'idle' to the
> vehicle computer of a modern car? It essentially seems like the tach
> input (with a multiplier).
> =

> I met someone yesterday who is having trouble with his start-up
> sequence because the vehicle computer thinks the engine is off and so
> it does not start the OEM electric power steering pump.
> =

> What he's tried:
> Attaching the OEM sensor to a fan with adequate gearing. He didn't
> like the mechanical dependency of this solution.
> Creating a 555-chip based circuit to drive a +/-12V pulse; but this
> keeps blowing on him.
> =

> Alternatives:
> Wire the power-steering directly into the 'ON' 12VDC bus?
> =

> The controller is a Curtis 1231C. I know the Zilla comes with a tach
> output on the hairball, what do people use for a tach when using a
> Curtis?
> =

> Thanks,
> =

> -Nick
> =

> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev

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## EVDL List (Jul 27, 2007)

> Peter Shabino wrote:
> > How are you "blowing" the 555? Are you running the 555 output directly into the engine computer or are you buffering/redriveing the signal first. Another thing to note is a lot of engine sensors (varies by car) are driven off weird voltages from the computer. If you drive a 12V signal in where they expected 8V 4V of that just gets drained to the 8V rail / reg thought the protection diodes. (and may explain why the 555 is dying).
> >
> > If you got a sketch of what your using feel free to send me a copy and I can see if there is anything easy you can do to harden it some more.
> ...


----------



## EVDL List (Jul 27, 2007)

Probably you are assuming that the 13.8V rail is 13.8V. It is not.
Expect to see any voltage from +100 to -200V on there, and protect
accordingly. You will need tranzorbs, capacitors, etc. We use
a tranzorb with a peak power capacity of 8kW, a clamp voltage of
27V (Vishay SM8A27). That clamps at 45V in a load dump situation!
Then we use a voltage regulator that will withstand a load dump.
A 7805 or 7808 won't, neither will a 555 run off the 12V rail -
for long. You need an automotive-spec voltage regulator -
Infineon's TLE4267 is one example. For reverse-polarity, you
can use a 5A, 400V silicon diode in series with the power supply
but before the tranzorb.

Also, ensure you have a series output resistor from the 555's output
to the ECM's input. Watch the grounding. Use clamp diodes, and lots
of decoupling. Put 100uF on the output of the voltage regulator.


-Dale

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## EVDL List (Jul 27, 2007)

> nicolas drouin wrote:
> > Hi,
> >
> > Does anyone have any leads for feeding a false RPM 'idle' to the
> ...


----------



## EVDL List (Jul 27, 2007)

Airbags and other mechanisms:

So how do folks handle the control of airbags etc, on modern conversions?

Are these independent and don't need information from the Engine Control?

thanks,

M
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## EVDL List (Jul 27, 2007)

On my Echo, there is a separate air bag computer that does not interface at all to the engine computer. I suspect this is to make it more reliable, especially during a crash. It is in the bottom of the dash, in the center, with short wiring to each air bag. It's powered by the ignition switch, and that is it's only connection to the rest of the car (other than a "fault signal" wire to the dash instrument cluster). 

So, it hasn't been a problem.

Phil Marino

> Date: Fri, 11 Jul 2008 06:04:46 -0700
> From: [email protected]
> To: [email protected]
> Subject: Re: [EVDL] Feeding a fake idle signal to the vehicule computer
> 
> 
> 
> Airbags and other mechanisms:
> 
> So how do folks handle the control of airbags etc, on modern conversions?
> 
> Are these independent and don't need information from the Engine Control?
> 
> thanks,
> 
> M
> -- 
> View this message in context: http://www.nabble.com/Feeding-a-fake-idle-signal-to-the-vehicule-computer-tp17982270p18403389.html
> Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.com.
> 
> 
> _______________________________________________
> For general EVDL support, see http://evdl.org/help/
> For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ev
> 

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## EVDL List (Jul 27, 2007)

> txhokie4life wrote:
> >
> > Airbags and other mechanisms:
> >
> ...


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## EVDL List (Jul 27, 2007)

I looked through the schematics on my 2001 Audi, and the ABS system 
has its own computer located under the center of the back seat. As 
far as I can tell the engineers at Audi/VW made a conscious effort to 
make the system autonomous so that if another computer failed it would 
still work.

The ABS may be different. Since it also works with traction control 
and stability control it interfaces with the engine computer. I'll 
figure that one out when I come to it...



> Robert MacDowell wrote:
> 
> > txhokie4life wrote:
> >>
> ...


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## EVDL List (Jul 27, 2007)

We're working on a 2008 Mazda 3 at the moment. I expect the vehicle
computers are similar. Not sure how much they have changed over the years.
We have succeeded in getting our steering pump to run and are working on the
rest of the dash signals. We plan on building a board that will do all of
the CAN bus stuff that we need to run the car.

Would anybody else be interested in such a thing? If you are working on
deciphering the CAN bus traffic, let us know.

Cheers,

Aaron Choate
REVOLT Custom Electric Vehicles

On Wed, Jun 18, 2008 at 10:24 AM, nicolas drouin <[email protected]>


> wrote:
> 
> > On 6/18/08, Barry Oppenheim <[email protected]>
> 
> ...


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## EVDL List (Jul 27, 2007)

I'll expand on what Aaron said, because I'm really pleased with our progress.

The Mazda 3, like a lot of modern cars, has replaced a ton of discrete
wires with computer to computer communications. In this case by a
pair of internal buses running CAN.

The bus we've been digging into is the power train bus. The
PCM/engine computer, the ABS computer, the Power Steering computer
(Mazda uses an electrohydrulic pump like the 90's era MR2's did) and
the Instrument cluster all have connections to this bus. The bus is
also carried to the OBDII diagnostic connector on the dash, which
makes it really easy to connect to for experimenting. Both buses are
carried to a connector hidden under the dash somewhere.

There is a second lower speed bus for the body, which has the ABS
computer, Radio, Climate Control, the Keyless entry receiver, an IO
expander in the fusebox above the passenger's feet and the instrument
cluster. The instrument cluster actually has a second onboard
processor that acts as a router between the two buses.

So when you press the AC button on the climate control system a
message goes over the Body bus, to the instrument cluster, onto the
Engine bus and on to the PCM. The PCM actually switches the AC
clutch. No electrical connection exists between the AC clutch and the
climate control system except the bus. Same with the keyless system.
The receiver does not control the door locks directly, it sends a bus
message to the IO expander, which closes a relay.

As you discovered the power steering computer will not power up the
90amp draw pump until it receives an engine running signal from the
PCM. Oddly, its actually checking for a bit to be set in the frame
that contains the tach and speed data.. it doesn't simply look for the
tach value to be > 0. Once the engine is started it varies the pump
speed based on either vehicle speed or tach, I'm guessing speed.

The instrument cluster has no connections to the harness except the
two buses, the turn signal indicators, the brake pedal switch and the
fuel sender (the latter two are actually sent out over the bus to
other computers although I've yet to figure out for what purpose).
The cluster gets vehicle speed and tach values from the PCM frame
mentioned above. All of the idiot lights, check engine, battery, ABS,
airbag etc are all turned on and off based on data received over the
buses.

Right now we're building a module that can replace the PCM. On the
Mazda (and most Fords) there is only one electrical connector joining
the engine harness (with the PCM) to the rest of the car. My goal is
to be able to unplug that connector, yank the engine and plug in our
interface instead. The interface will have all the required
inputs/outputs to interface to typical controller.

Right now there are still a few things we're trying to figure out. On
non-ABS equipped cars the transmission has a vehicle speed sensor,
which is read by the PCM (manual) or the transmission control computer
(auto). On our ABS equipped vehicle there is no speed sensor. The
ABS computer measures vehicle speed using its own wheel speed sensors
and send that data to the PCM in a frame we haven't identified yet.
The PCM then integrates that data with the tach data and sends out the
frame that controls the instument cluster gauges and the power
steering pump (which we have identified). We have a good idea of what
frame is sent by the climate control system to request the AC clutch
be engaged but haven't been able to confirm it yet. We can turn on
and off all of the idiot lights on the dash, but in the case of the
ABS light the ABS computer just turns if back on (causing it to
flicker). Which is our last problem, the ABS is storing a
"communication failure" trouble code, and we don't yet know why. We
suspect its expecting some data from the PCM that we are not yet
providing.

Ford supposedly has a "corporate bus format" so the data we've
gathered may turn out to be relevant for other Ford and Mazda cars
built on CANbus.

The one thing we haven't spent a lot of time on is the accelerator
pedal. The Mazda is a throttle by wire car, so we'll need to come up
with a way to convert that signal into something that will interface
with a Hairball. If anyone has information or a circuit please let me
know.

We'll probably end up opening this data up once we're done, and we'd
love to help leverage this knowledge to open up other vehicles.
Please get in touch with either Aaron or I if you have a similar
problem or if you have additional data to contribute.

You can get high quality wiring diagrams for Mazda products at
http://www.mazdatechinfo.com/. Most of them are available on a
subscription basis for $20/day.


Mark Farver


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## EVDL List (Jul 27, 2007)

> Nick Drouin wrote:
> >
> > The controller is a Curtis 1231C. I know the Zilla comes with a tach
> > output on the hairball, what do people use for a tach when using a
> ...


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