DHS on mk3.75

Technical Area Electrics & ICE
2

HiĀ 

i have had a look around and cant seem too find any info on disabling the systemĀ 

so i thought i would post and ask the questionĀ 

my worry is it going off on a track session with a small nudge and destroying the bonnet so disabling it would be niceĀ 

any ideas would be greatĀ 

thanks in advanceĀ 

PaulĀ 

3

You can pick your way through this thread but I donā€™t think thereā€™s an answer to your question.

https://www.mx5oc.co.uk/forum/yaf_postst104649_Active-Bonnet-issue.aspx?=

Ā 

It relates to the ND (Mk4) but relevent on your model too. I would tend to believe you canā€™t disable it say like traction control, it is a safety feature after all. Just imagine if you did and hit something or more to the point someone??

The only way I would imagine it could be disabled/removed is if you had a full time track car and the expertise.

4

Hello Paul20v

Give Roddison Motorsport S9 1US 0114 244 5300 ask for Paul.

Regards

Keith

5

I am not near my ND4 at the moment but if I was concerned for track use I would look at unbolting the actuators and repositioning them in such a manner that if actuated they would punch a hole in fresh air.

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1 Like
6

HiĀ 

thanks for the replyā€™sĀ 

I had a feeling it wasnā€™t going to be easy as it shouldnā€™t beĀ 

a dedicated track car itā€™s definitely not but at the same time it would be nice if you could disable it for track useĀ 

I had thought about moving the actuators so I will have a look at that optionĀ 

i will see if thereā€™s room too point them somewhere else so they wonā€™t bash anything else as I donā€™t know how much they open upĀ 

i donā€™t want rid of the system for the road just the track not that I think itā€™s going too make my car dangerous without it no worse anyway than a car that doesnā€™t have it fittedĀ 

thanks for the replyā€™s itā€™s much appreciatedĀ 

??

Ā 

7

Hi all

just too follow this up just in case anyone is interestedĀ 

the actuator plugs can be unplugged and a 3 ohm resistor but across the terminalsĀ 

obviously this is done with the battery disconnectedĀ 

the system then thinks the actuators are still there and no light shows on the dashĀ 

this can then be unplugged and returned too normal after returning to the public roadsĀ 

cheersĀ 

PaulĀ 

Ā 

8

Thank you, Paul, for sharing your experience! I have the same trouble. 

A couple of questions. 

What do you mean here: ā€œthe actuator plugs can be unplugged and a 3 ohm resistor but ACROSS the terminalsā€ - is it enough just to close the connectors in each terminal with a relevant resistor? 

How did you find the specific figure of 3 ohm - by making an experiment?  

 

 

9

Hi 

yes exactly that , unplug the yellow plugs and at the cars loom side put the resistor across the terminals 

if you shape the resistor wire they just push straight in the plug terminals nice and snug 

i got too the 3ohm resistor via knowledge of airbag systems they normally range between 2.2 - 3.2 ohms 

so it was an experiment but not too much range too worry about and i finished off at 3 ohms 

you wont do any harm too the dhs control unit with resistors just dont try and measure the actuators with a multimeter as you might find out how they work ??

 

Hope this helps 

cheers 

paul 

10

Thank you so much, Paul for your detailed explanation!Ā 

Thatā€™s the only useful informationĀ about deactivation of miata active bonnet system that Iā€™ve found in the web .Ā 

Iā€™ll try do do this soon and will share my experience here.Ā 

11

Your welcome ??

12

Hi Paul!Ā 

Your method really works, Iā€™m so grateful to you!Ā 

Now I wonder what happens if the system registers a relevant impact - does it turn on the control lamp on the dashboard anyway? Does it fire the actuators after you connect the wiring again? Does the event stay in the memory of the control unit? I wish nobody to prove all the above mentioned, but maybe anyone knows?

Itā€™s also a bit tricky to disconnect the connectors - the secret is to hold the yellow housing and to push white element downwards at the same time.Ā 

And concerning returnig things to the initial state after track sessions - imho this is the matter of conscience of the car owner and thereā€™s nothing more to discuss. Thousands of Miatas 3.5 and older run the roads and nobody blames their owners.Ā 

Ā 

13

Hi 

in relation too the system registering an impact and holding it in a memory in my opinion i wouldnt have thought so , for the simple reason the control unit is self reseting as no intervention with diagnostic equipment is needed to reset the light after it was flashing on the dash registering a fault with the actuators disconected it was just a matter of putting in the resistors cycling the ignition and the dhs light went out 

if for example it was an airbag system they dont reset automatically they need the codes clearing with diagnostic equipment before the light and fault codes dissapear , the hood sytem has no such issues .

cheers 

Paul 

14

Thanks, Paul! Now thatā€™s clear. Good luck to you and your Miata

15

Thanks , you too 

16

I know this is a old thread but just to clarify a few things regarding the mazda mx5 mk3.75 dhs system

if the system is activated in a accident and the actuators go off the dhs module is NOT self resetting and in my experience it is also not resettableĀ via a diagnostic computer it may be able to be done at a mazda main dealer I have not tried that so this could mean the dhs module has to be replaced and also I have never been able to find the moduleĀ in the car if anyone knows where it is then please send me aĀ message

the dash light will remain active if any of the following are not connected

the front crash bar sensors in the front bumper connection passengerĀ front next to the fog light plug

the bonnetĀ actuators

or the system has activatedĀ previouslyĀ even after the front crash sensors or the bonnet actuators have beenĀ replaced

Ā 

17

 

MX5Parts have the module listed on their site and the description states it needs to be replaced following activation. No idea where it is though and mine doesnā€™t have DHS fitted.

18

From memory, its behind the drivers seat

19

Old thread, but wondering if someone can confirm that the system resets on a ND after triggering with the resistor in place.

I understand that the warning goes away when you plug everything back in without the system being triggered, but wondering if the module survives a ā€˜blank shotā€™.

In either case its probably cheaper to replace a module then the entire DHS after a trackday :stuck_out_tongue:

20

Hi all,
Bump on this thread.
Iā€™m interested to know as well on a triggered system if anyone been able to reset the module or remove dash light using the resistors method ?
Thanks