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Stop/Start Disabled on Startup - Success

25K views 37 replies 22 participants last post by  Sampson0420 
#1 ·
I finally got around to building my circuit that disables Stop/Start upon startup. It seems to work! - in the garage - I've yet to try it on the road.
Here's a video of it lighting the disable light 5 seconds after startup. The button is still usable to reactivate the Stop/Start if desired. No DTCs are displayed (just low gas).

Here are some details for the techie folks...

I've included a picture of the circuit diagram and the circuit itself.
The circuit is basically one of these connected to a SPST relay which connects to both pin 8 and pin 10 of the headlamp switch module through separate resistors. When the relay is active, it connects the pins to ground through their respective resistor.
Each pin has a separate non-pressed and pressed resistance. I guess this is to help the Body Control Module detect open connections or shorts. The values of the resistors used in this circuit are calculated to match the normal button press value when run in parallel with the non-button press value.

The timer has to be programmed through a procedure to make the appropriate pulse after 5 seconds. I used timer function 7 with a t1 of 6 seconds and t2 of 1 second. Once programmed, it retains the function indefinitely.

I used these which match the diameter of the wiring harness wires. They allow easy removal of the circuit if needed. This is the I used. This has the two values needed - 1900ohms (I used 2K) and 675 ohms.

Installing it is a little tricky. The headlamp switch module prys out. There are four spring loaded clips in the upper right, upper left, lower right and lower left. You have to gently alternate prying on these four spots little by little. Don't pull on the chrome ring around the knob - it comes off easily. This reveals the connector which can be unplugged to install the t-connectors to the appropriate wires. The diagram is from the perspective of looking at the connector from the back side where the wires come out. I pushed the relay and timer through the opening in the dash frame zip-tied it to keep it from rattling.

If anybody else wants to try this I'd be happy to answer questions. It does require some soldering skills and some basic electronics knowledge would be helpful. Testing on the bench should be done before install.
 

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#3 ·
Great work!!!

I think the different resistance is the way the CAN bus works. But you already sorted that out!!!

Thank you for sharing this. I’m not very good at soldering so for now I’m going to press the button when I remember to, until I get brave to try.
 
#5 · (Edited)
I finally got around to building my circuit that disables Stop/Start upon startup. It seems to work! - in the garage - I've yet to try it on the road.
......
If anybody else wants to try this I'd be happy to answer questions. It does require some soldering skills and some basic electronics knowledge would be helpful. Testing on the bench should be done before install.
Good idea, well done :cool:. I did something similar in the past for the ASR switch on my 147 GTA, if I get round to it I can probably just use/adapt it for the start/stop ;)
taking the start/stop button/panel out is what held me back till now ;) (and hoping that disabling it via OBD would be available short-term)

just as an example, see:
http://home.planet.nl/~jwq/temp_gta/asr_switch_instructions.pdf
 
#6 ·
As a Retired Broadcast Engineer I tip my hat and bow to you and say THANKS, MANY THANKS.

I thought about using a delay timer, but have been to lazy to to do it.
Rich
 
#10 ·
Brilliant effort. I'm content simply pressing the button when I don't want start/stop.
 
#12 · (Edited)
You found a niche product

I watched your video. Bravo! You should build a business around this product. Especially, if most manufacturers accomplish this with similar CAN bus technology. There are plenty of MB E-Class owners that would appreciate this device. Choose a similar vehicle, one where the manufacturer will literally produce over 1-million examples over the model production run. You could probably rent an example from a major fleet, for a few days, to R&D the product.
 
#13 ·
Good news is that the module works on the road. The Auto start stop is disabled after a normal in-car start.

Bad news is that remote start is unhappy. Apparently it doesn't like someone being in the car an pressing the S/S disable button when it's under the remote start procedure. As soon as the timer kicks in, the car shuts off. These cars are too smart!
 
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#18 ·
I only have less than 1k miles on my 2017 Giulia (sport). I observed that some day the auto s/s works some day not. There are more days it is not working than it do.
Question: is this function activated depending on outside temp, engine or any other conditions? if it is not working (not shut the engine) is it a malfunction ( a welcomed one) or just has its own logic (mind)?


Thanks.
 
#19 ·
Question: is this function activated depending on outside temp, engine or any other conditions? if it is not working (not shut the engine) is it a malfunction ( a welcomed one) or just has its own logic (mind)?
Page 47 of your owner's manual shows what conditions can cause the Stop/Start system to deactivate:

"Stop/Start will deactivate in the following scenarios:
- The climate control system is in AUTO mode (indicator illuminated), and the vehicle has yet to reach the set temperature
- The climate control system is in LO maximum cooling
- The climate control system is in HI maximum heating
- The climate control system is in the MAX-DEF status

When the Stop/Start system is active, the engine will restart if the inside temperature changes significantly, or if the LO setting, or MAX-DEF setting, is activated."
 
#20 ·
I live at 6500 feet, Lake Tahoe, and my Start/Stop never functions at this altitude. The algorithm that analyzes the air mix apparently decided their is insufficient oxygen at this altitude. I soon as I drive down to the Carson Valley it begins to function again. FWIW
 
#24 · (Edited)
From the service manual:

Engine Failure to Stop Conditions
When the ESS system is active, the engine may not stop in some conditions for reasons of comfort, emission control and safety. These conditions include:
- Engine temperature is still cold
- Battery is not sufficiently charged
- Windshield wipers are being used at maximum speed
- Driver’s door is not shut
- Driver’s seat belt is not fastened
- Vehicle is in the reverse gear(e.g. parking maneuver)
- When Automatic Temperature Control (ATC) is equipped, a desirable level of comfort has not been reached
- Barometric pressure (over threshold)
A message will appear on the instrument panel display in these cases.

Engine conditions that disable Autostop
When the ESS system is activated, there are specific conditions that will prevent the ESS system event to occur. The following conditions leading to an ESS system operation preventiont can be detected and managed by the BCM or the PCM:

Cold engine: Autostop is prevented if the Engine Coolant Temperature (ECT) sensor is outside of a range of 40°C (104°F) and 100°C (212°F). In this case, the fuel efficiency and emission reduction deriving from use of the ESS system is not guaranteed .

Reverse gear is engaged: the PCM will not allow the automatic stopping of the engine if reverse gear is engaged . This measure has been adopted in order not to adversely affect performance during parking maneuvers.

A malfunction or fault detected in at least one of the following components will also disable the ESS system:
- Accelerator Pedal Position Sensor (APPS)
- Brake pedal position sensor
- Automatic Braking System (ABS) Hydraulic Control Unit (HCU)
- ECT sensor
- Wheel Speed Sensors (WSS)
- Engine crank sensor
- Engine camshaft sensor
- Reverse switch
- PCM (Malfunction Indicator Lamp/MIL on)

The BCM will signal prevent the engine automatic stopping by sending a CAN-C data bus network message if one or more conditions managed by the BCM occur:

Battery not being sufficiently charged
- IBS calibrating
- SOF of the battery is below 8 .3 V
- Battery temperature is below -23°C (-9°F)

If the IBS is not calibrating, Autostop will be prevented if one of the following conditions occurs:
- SOC is below 75%
- SOH is below 60%
- SOF is below 8 .2 V
- Battery temperature is below -23°C (9°F)

IBS fault: The automatic engine stop event is prevented if an IBS malfunction occurs.

Driver’s door not shut: Autostop is prevented if the driver’s door is open .

Driver’s seat belt not fastened: Autostop is prevented if the driver’s seat belt is not fastened .

Outside temperature sensor: Autostop is prevented if:
- Outside temperature is lower than -16 °C (3°F)
- Outside temperature is higher than 82 °C (180°F)
- NOTE: The temperature limits that have been set on the outside temperature sensor are “extreme” and therefore must always be considered .

ATC: Autostop is prevented if the difference between the climate control temperature set by the customer and the temperature inside the passenger compartment is greater than ± 4°C (39°F)
NOTE: If the vehicle is equipped with manual air conditioning, the engine can always be Autostopped .

Generator fault: Autostop is prevented in the case of generator malfunctions.

Hood open: Autostop is prevented if the hood is open.

Logistic Mode status active: Autostop is prevented if the Logistic Mode status is active.

BCM relay fault: Autostop is prevented if there is a starting circuit relay issue. The relay is operated by the BCM.

Steering position: Autostop is prevented if the Steering Angle Sensor (SAS) is out of calibrated range.

Fuel level: if the fuel level is below a certain threshold, Autostop is disabled
 
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#26 ·
Just a follow-up note on this method. I've modified the circuit that I showed on the first page which ended up causing a DTC. My new circuit uses two relays. I'm also now placing the circuit near the Body Control Module (BCM) located under the passenger side floor mat. It's been working well in my car for a couple weeks now. No warning lights or DTCs. Unfortunately, it still has the side effect of disabling remote start.
If anybody is interested, let me know and I can post the updated circuit.
 
#30 ·
Do you think it's possible with more development to attach a circuit input that tells your circuit when the car is in "remote start" mode? That input can disable the timer until the car is no longer in "remote start" mode. I don't know anything about car computer hardware, but I know that, at least in my Charger, the push-start button blinks in the "On" mode when in remote-start mode, so I know the car is projecting that as a specific mode.
 
#29 ·
Ok, The updated circuit is attached. It's basically a two-relay version of the previous circuit. The problem with the previous one was that when the relay was deactivated, there was a resistance path between pin 8 and pin 10 of the headlamp connector. I guess the BCM didn't like that after a while. Since two relays made the assembly too big to fit behind the headlight switch, I hooked into the wires as they entered the Body Control Module (BCM) which is located under the passenger's feet, behind a panel. I've attached a diagram of the several connectors that go into the BCM. I just used C5 and C8. I connected the red wire of the timer module (activate) to C5-26 which is an ignition wire, dark blue with a thin stripe of white. One relay output going through the 1900 ohm resistor goes to C8-28 (Wh/Rd) and the other relay output going through the 675 ohm resistor goes to C8-40 (Wh/Gy).
I connected the ground of the circuit through a toggle switch to a screw under the dash.
 

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#32 ·
I finally got around to building my circuit that disables Stop/Start upon startup. It seems to work! - in the garage - I've yet to try it on the road.
Here's a video of it lighting the disable light 5 seconds after startup. The button is still usable to reactivate the Stop/Start if desired. No DTCs are displayed (just low gas).

Here are some details for the techie folks...

I've included a picture of the circuit diagram and the circuit itself.
The circuit is basically one of these mini timers connected to a SPST relay which connects to both pin 8 and pin 10 of the headlamp switch module through separate resistors. When the relay is active, it connects the pins to ground through their respective resistor.
Each pin has a separate non-pressed and pressed resistance. I guess this is to help the Body Control Module detect open connections or shorts. The values of the resistors used in this circuit are calculated to match the normal button press value when run in parallel with the non-button press value.

The timer has to be programmed through a procedure to make the appropriate pulse after 5 seconds. I used timer function 7 with a t1 of 6 seconds and t2 of 1 second. Once programmed, it retains the function indefinitely.

I used these t-connectors which match the diameter of the wiring harness wires. They allow easy removal of the circuit if needed. This is the relay I used. This pack of resistors has the two values needed - 1900ohms (I used 2K) and 675 ohms.

Installing it is a little tricky. The headlamp switch module prys out. There are four spring loaded clips in the upper right, upper left, lower right and lower left. You have to gently alternate prying on these four spots little by little. Don't pull on the chrome ring around the knob - it comes off easily. This reveals the connector which can be unplugged to install the t-connectors to the appropriate wires. The diagram is from the perspective of looking at the connector from the back side where the wires come out. I pushed the relay and timer through the opening in the dash frame zip-tied it to keep it from rattling.

If anybody else wants to try this I'd be happy to answer questions. It does require some soldering skills and some basic electronics knowledge would be helpful. Testing on the bench should be done before install.
Just saw this....... great job!

You don't happen to have another one laying around, do you?:wink2:
 
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