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Observation: EGas Shuts Throttle When...


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Tony: When you read "blip" think "heel & toe" as in using your heel/side of the foot on the gas pedal to bring the revs up while your toes are mashing the brakes.

heel toe is really a misnomer these days. What you are really doing is braking(depressing brake pedal) with the left half or so of the ball of the foot, then while at the same time rolling your foot(right half of the ball) to make contact with the gas pedal so that you can blip it while keeping consistent foot pressure on the brake. Takes practice...but makes for the smoothest possible downshifts since the revs with some practice will match the wheel speed when done correctly. It keeps the car in perfect balance without upset when done right...(no herky jerky) and allows you to start accelerating throughout the corner after turn in, in the correct gear. It also lessens clutch wear when done properly.

Edited by rockitman
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  • 4 weeks later...

Guys this may help.

E-Gas is on C4's since 1999 and all models as of 2000.

E-Gas does not intefere with heel and toe at all.

E-Gas will cut the throttle back to idle if you press the brake pedal while still calling for power. Power is cut after about 1.5 seconds.

E-Gas will not cut power if you are braking and then press on the gas pedal. That's why blipping the throttle to match revs for heel and toe downshifts still works.

E-Gas will permit braking while you apply power as long as the brake pedal is pressed first. If the reverse, E-Gs assumes the engine has run away due to electronic failure.

Hope this helps understand how it works.

Best,

Bob

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If I understand all of this correctly you just need to be out of the gas completely within the 1.5 secs, then you can get back on it, and balance the two, so long as the brake pedal remains within the same stroke as far as it's brain is concerned. If you get all the way off the brake you need to start the process again.

I followed this diagram to set my brake pedal around 10mm lower than it was delivered, and it has transformed the way the car feels. There was a really big step between the two, making heel toe and transitioning between the pedals very awkward. Now everything is in the right place the foot work is smooth and easy, and the car feels much smoother and calmer.

post-3-1080789970_thumb.jpg

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  • 9 months later...

I've made progress on a hack. Pull fuse B9. Doing so disables the egas kill feature as well as ABS, but proper stop light function remains. You also get console warning lights, but they go away when you reinstall the fuse.

Looking at the wiring diagrams, wires run from the brake pedal switch to the ABS control unit, but not directly to the ECU. There is however a wire running from the ABS control unit to the ECU labeled "ESO rear". My guess is that under braking the ABS unit tells the ECU to cut throttle via this wire. Hence by disabling ABS, the throttle cut signal is not sent.

My next experiment is to locate this wire and tie it to ground. The ABS unit itself is located directly behind the left headlight. Pop out the headlight to see it. Unfortunately the wiring is not easily accessible there, but I believe it may be accessible under the plastic covering over the left front strut mount.

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An update:

- I was mistaken about the location of the ABS CU. It is not behind the left headlight as I previously posted. Rather it is just to the left and in front of the brake fluid reservoir. Remove the plastic cover over the reservoir and you will see the CU on the front of the brake hydraulic value assembly. Wiring is connected to the CU via a large black Bosch connector.

- I realized what the wire label "ESO" likely stands for: Emergency Shut Off. So I am pretty sure that this is the wire that needs to be hacked. If you untape the bundle of wires leading to the Bosch connector, it is the one colored white with a brown stripe and connected to pin 19 of the connector. There are actually two wires with this color in the bundle. The one that is twisted together with a blue/brown wire is part of the wheel speed sensor circuit. That is not the one involved with ESO. The white/brown wire that runs straight and untwisted in the bundle is the ESO.

- According to the wiring diagram, the ESO circuit is also connected to the trunk latch mechanism. I think that if the trunk entrapment release is pulled, the ESO will cut throttle also. An ESO wire also runs to the xenon headlight CU, I have no guess as to what effect ESO has on the lights. On non-GT3 PSM equipped cars, ESO also connects to the PSM CU.

- I am still not yet ready to cut and ground the ESO. I want to think more first. Maybe I am still missing something that should be obvious. :help:

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I had another thought. Looking at Xenon CU diagram, the three ESO wires from the the ABS, PSM and trunk entrapment are simply tied together. This says to me that cut ESO wires should be left floating rather than tied to ground (or alternatively to power). It seems to me that tieing it off would be equivalent to a short circuit, while leaving it floating would be equivalent to an additional, unused input source. So I think what I am going to do next is to try cutting the dang thing. If that works then I will install an inline switch: open the connection to defeat ESO, and close it to restore ESO operation.

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Success. The ABS ESO defeat hack works. :clapping:

Simply cut the straight, untwisted white/brown wire in the ABS CU wire loom bundle.

There are no side effects. All brake and throttle functions continue to work properly, and there are no console warning lights.

The only change is the defeat of the ABS Emergency Shut Off function. So you can left foot brake freely while staying on the throttle without the worry or annoyance of having the throttle cutting out.

Here are the instructions:

- Release the trunk's left side carpeting. See page 163 in the owner's manual.

- Remove the black plastic cover surrounding the brake fluid reservoir. There are three screws on the top and one plastic connector on the lower edge. When you lift away the cover take care not to damage the interior light wiring that connects to the cover.

- Just to the left and in front of the brake fluid reservoir you will see a large Bosch wiring connector. Release the connector by lifting up on the handle. As you lift a locking mechanism will slide outward to the left along the lower edge of the connector. Help it slide out with your free hand.

- The wiring bundle connected to the Bosch connector has two parts, a thicker part wrapped with black tape and a pair of separately wrapped brown wires.

- Untape about a four inch section along the thicker part.

- Find a wire colored white with a brown stripe. There are two wires in the bundle so colored. You want to find the one that is straight and untwisted. This is the ABS ESO wire. The other wire is twisted together with a blue/brown wire. That is not the one you want. You want the straight, untwisted one.

- Cut this wire. Leave the cut ends of the wire floating, and tape them individually to avoid a short circuit. Alternatively, you might want to install an inline switch so that you can easily restore operation.

- Retape the bundle, reinstall the Bosch connector, the plastic cover and the side carpeting.

- That's it.

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Update: I got a CEL yesterday, after a week of running ESO off and ABS off alternately. Apparently the DME does sense the situation and although not immediately, after some number of engine cycles, does throw a CEL.

PST2 reports the following 3 faults, DME: P0501 Vehicle Speed, ABS: 4275 Valve Supply Voltage and Instrument Cluster: 9111 PSM/ABS Control Unit.

Because I pulled both ABS CU and valve fuses as well as the ESO, it is not clear which of these is related to which faults. Presumably powering down the ABS may cause any of them, but I am not sure what just the ESO, by itself, causes. Clearly the DME senses the loss of ABS speed input when the ABS is off. But when it is on does speed date get transmitted on the CAN or on the ESO? My guess is CAN, since ESO is sourced elsewhere, but I'm not sure.

I am going to do some more testing and see if I can find out more. It may well be that if you want no ABS or no ESO, you will have to live with CEL.

Edited by mds
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I think the only fault type that can throw a CEL is the DME (Pcodes). P0501 is a type 1 fault and will definitely cause a CEL. Why that is considered an emission fault is beyond me. The other faults should cause an ABS and or PSM light (if you have PSM).

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Loren, I agree, those other faults (and the ABS and brake warning lights) were probably caused by my ABS fuse pulling experiments. With all fuses reinstalled, and all faults cleared, I left the ESO cut and am running the car. No CEL yet. I bought a cheap scan tool today, as soon as it arrives I will check for any pending Pcodes. My guess at this point is that I probably will see one. If so, bummer, although I guess you could always use the scan tool to reset it. If not, great. We shall see.

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Cutting the ESO does throw a CEL after 6 to 8 drive cycles. The DME does detect the loss of communication with the ABS CU when the ESO is cut. Although I have not done another scan, no doubt the fault is P0501, like before. So lacking another alternative, if you must have no ESO, you either live with CEL or the need to reset it repeatedly. :(

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I checked the DME 7.8 diagnosis manual. The fault P0501 is listed as "Vehicle speed - open circuit." One of the possible fault causes listed is an open circuit on the ESO wire that I cut. So the bottom line: Cutting the ESO does disable the throttle cutoff when left foot braking, but you will get a P0501 fault code and a check engine light as side effects. So far I have seen no other side effects, everything else, the brake, throttle, and ABS continue to work fine.

By the way, Kragen Auto has the easy to use Equus OBDII code reader on sale for $99. It displays the codes, both active and pending, and allows you to erase them and reset the check engine light. I tried it on a Jaguar, two Toyotas and my GT3. It works fine on all of them.

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  • 1 month later...

An update: I've been running my cut wire hack for a month now. It works great with no problems, other than the check engine light. When I reset the light, it comes back after two drive cycles. I decided to install a switch so that I could reconnect the wire whenever I have the car serviced. This one works well. After soldering the wires, I zip tied the switch onto the lower part of the ABS control unit bracket.

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