URGENT help needed ! key fob/alarm.

StuC · July 3, 2014, 13:19

Might be time to whip it out and check the connections then.

Nchillin75 · July 3, 2014, 13:43

question: are the key and the fob both based on the same chip? apologies I don't know how key coding works. But I would imagine as their is only one circuit board in the fob, they are the same? so if the key can be coded to the car but the fob can't, gonna have to presume the fob does work but I'm rubbish at synchronising the last section of the key coding element. i.e. the two button fob push

phils99 · July 3, 2014, 13:59

the key has a build in transponder the same as a non button key, one stage of the programming is to "pair" up the key transponder to the ignition switch.

The second part is to then pair up the radio transmitter for the push buttons to the car. this is the part I think the guys need to do to get the fob working.

The whole security system works from a seperate ECU which connects to the cars ECU.

I know this as I change a cars full security system out as my car only has the grey key which means you cannot reprogram any keys.

So I bought a full set off ebay with the fob key, ignition switch, ECU, door lock barrels, floor levers lock and the glove box lock (he didnt have the rear box locks available) and had to replace mine with all of that!

afterwards it all worked great!

StuC · July 3, 2014, 14:29

Interesting there Phil that you dont mention the alarm unit (the one under the bins) in the bits you have replaced.

phils99 · July 3, 2014, 14:32

you know, I cant remember if I did replace this, but I think I must have done, this is the interior sensor and I would think be a generic part not specifically coded to a car.

phils99 · July 3, 2014, 14:41

reason I say I cant remember, is because I also bought a second MR2 PFL and this didnt even have an alarm fitted!

I had to buy a 2 button key fob pre cut and pre transponder coded to my car from CTP (£130!!) as I only had a black key for the car.

I then found the full wiring loom wiring, ECU, interior sensor, siren and the "plungers" for the bonnet and engine lid as a kit on ebay and fitted these, which then required coding...endless hours of opening and closing the door and inserting the key in the ignition!.....so you see I have had endless fun with the Toyota alarm systems in the MR2!!

But if anyone else on here has an MR2 without an alarm fitted, this can be retro fitted and I also have a brilliant doc from Toyota detailing how to do it and all parts needed. Take note that Toyota no longer supply the retrofit kit as myself and Chris from CTP found out the hard way!

StuC · July 3, 2014, 14:41

I would have thought it was a generic part too.
Not sure how in depth people have looked at this component before.

phils99 · July 3, 2014, 14:51

yes...it is pretty well hidden, but it also has an adjuster on it so you can decrease/increase the sensativity.

For those who dont know, when the alarm is enabled, this "hidden" unit sets up a wave field in the interior of the car, if someone reaches in to say grab your bag from inside, it will detect an obstruction in the wave field and set the alarm off...clever!

carolineasb · July 3, 2014, 15:14

Think the interior "waves" are only when you have done 3 "clicks" on the locking button?

Nchillin75 · July 3, 2014, 15:14

well - with enormous amounts of sound dampening towels and blankets I will tackle this tonight. Can we just confirm the correct method of pairing for the 2003 onwards? I appreciate there are several documentations of this.

I also bought a cr1616 just in case it is the battery lol

phils99 · July 3, 2014, 15:17

cant you just open the frunk, remove spare wheel and pull the wire out of the siren? This will allow you to work on it (indicators will flash to show alarm is going off)

Nchillin75 · July 3, 2014, 15:18

Phil

is it also possible based on the separate transponder and radio transmitter to find someone with the alarm ECU (lovely if he had working fobs with it) replace it and pair a new set of fobs?

The key transponder wouldn't change so the Engine ECU wouldn't need replacing...

Nchillin75 · July 3, 2014, 15:42

ref wires out of siren - another obvious solution s:)

s:) will do

StuC · July 3, 2014, 15:46

I just wondered if having it connected to the system whilst you are diagnosing it is important. There is more than a couple of wires going into the sounder, so it's not just a power and ground.

phils99 · July 3, 2014, 15:56

Neil,

the key, transponder and fob is all one piece, so maybe, you could get another alarm ECU and using the supplied key fob take the insides out of it and put it in your key fob....

But, honestly, if you follow the programming guide, you should be able to get the one you have working unless it is actually not sending a signal but just lighting the little light on the key everytime you press a button.

Nchillin75 · July 3, 2014, 16:03

that programming guide, is there definitive answer on the method for 2003 onwards. Sorry to repeat. I've seen three versions now. s:)

s:)

StuC · July 3, 2014, 16:06

As far as I know it works for all years.

Nchillin75 · July 3, 2014, 16:11

c. 3 times for CONFIRMATION mode.

out of interest what is this mode?

add is obvious - rewrite suggests replacing a key if the ECU is full

and I figure you need to go through the full process of coding the key before coding the transmitter?

you can't just skip to the transmitter?

StuC · July 3, 2014, 17:26

There was a thing I found out relating to the number of keys programmed to the ecu. I think it's 4 off the top of my head.
I had to clear those on mine before I could reprogramme mine.

Nchillin75 · July 3, 2014, 18:54

Right all,

I can tell you now that thatcham obviously covered off the disconnecting of the alarm horn. And however quiet you think it is in the stock position, its ridiculously loud with your head next to it!

it also refuses to stop until you reconnect it!

Anonymous · July 3, 2014, 19:12

It will have a battery back up to stop someone disconnecting it to shut it up if trying to steal the car

Nchillin75 · July 3, 2014, 19:22

yes I realised that when I disconnected it

ok I've tried the pairing sequence for black and grey key / fob - nothing works. also note - replacing the fob battery makes no difference either, or blipping it in various places around the car.

Auto Electrician I think.

carolineasb · July 3, 2014, 21:57

Silly question but have you actually checked the car's battery?

onion86 · July 4, 2014, 08:32

Quote from: "carolineasb"Silly question but have you actually checked the car's battery?

I think that base is covered as the car starts fine, if there is enough power to start it then there is definitely enough for the fob to work.

carolineasb · July 4, 2014, 12:18

Just first thing that my hubby (Mechanic) said. Electrical problems with battery and alternator can cause problems with alarm.