How does one replace a transponder in a 2002 Forester?

[Tom Crabbe]

Background: 2002 Forester just passed MOT. Both key fobs were "in & out" on central locking - batteries replaced - still very hit and miss. Garage reckons transponder is on the blink.

So the question is: Is there a fix or is it a replace - in which case does one have to reset the keys or find the code from the keys themselves to put in the transponder.

Anyone know the form or had a similar problem.

Is there a work round rather than having a man charge me the price of the car to fix the central locking?

Many thanks

As always your help is appreciated.

[Jay762]

Tom - just to clear something up - some Subaru alarms suffered interference if they were close to an antenna. Can we rule that out in this case?

 

You can reprogramme using the keypad, so if you need to replace the fobs you can - problem is I dont think the transponder is a separate unit.

 

here is a picture of the M30 alarm you can see key fobs, sensors, siren and ECU but no separate transponder unit

 

 

[Mr B]

Do you have the M30 or M20 Sigma Subaru alarm option or do you have the standard remote locking fob with just the chipped key immobilizer system.

Basic quick points below kind of relate to both alarm options but need a lot more details on fault to be more precise in commenting.

Are both key fobs causing same issue ? if so highly unlikely it issue with the fobs.

What exactly is the issue in finer detail? If simply doors are not always unlocking, first thing to do is see if alarm is actually turning off even if doors didn't unlock, so unlock drivers door using the key and perhaps siren will go off (if on M30/M20 alarm), also start car to be sure alarm immobilisers are off & functioning ok but purely central locking the iffy part. Point being if alarm is fully off the alarm itself is not faulty but the cenral locking is & you best getting a decent clued up mechanic or auto electrician to have a look & start from drivers door as this is activated via remote & then signals the rest of the door locking motors.

as mentioned above interference from likes of mobile antennas can cause issues but if having these issues at several locations then highly unlikely, if alarm is actually not turning off then issue with alarm receiver/antenna or alarm electronic mainbrain is possible.

Obviously just using the key on the drivers door to test the locking & unlocking for a few times will help to diagnose what at fault too as if work all the time via the key then likely the initial driver door locking motor at fault.

Transponder is normally term associated to the chip with the key that disarms the immobilizer via proximity to a sensor near the ignition barrel. if doors are locking then unlocking when pressed I would be checking basics of central locking function first & if on the basic standard alarm the fob is purely remote central locking in reality with a separate transponder chip that purely works with immobiliser.

M30/M20 alarm has a reset procedure which might be worth looking into & I suspect details on this are in a thread already if need.

[Tom Crabbe]

Tom - just to clear something up - some Subaru alarms suffered interference if they were close to an antenna. Can we rule that out in this case?

 

You can reprogramme using the keypad, so if you need to replace the fobs you can - problem is I dont think the transponder is a separate unit.

 

here is a picture of the M30 alarm you can see key fobs, sensors, siren and ECU but no separate transponder unit

 

 

Hi

There is no alarm, just the two keys with Lock and Unlock buttons

[Tom Crabbe]

Do you have the M30 or M20 Sigma Subaru alarm option or do you have the standard remote locking fob with just the chipped key immobilizer system.

Basic quick points below kind of relate to both alarm options but need a lot more details on fault to be more precise in commenting.

Are both key fobs causing same issue ? if so highly unlikely it issue with the fobs.

What exactly is the issue in finer detail? If simply doors are not always unlocking, first thing to do is see if alarm is actually turning off even if doors didn't unlock, so unlock drivers door using the key and perhaps siren will go off (if on M30/M20 alarm), also start car to be sure alarm immobilisers are off & functioning ok but purely central locking the iffy part. Point being if alarm is fully off the alarm itself is not faulty but the cenral locking is & you best getting a decent clued up mechanic or auto electrician to have a look & start from drivers door as this is activated via remote & then signals the rest of the door locking motors.

as mentioned above interference from likes of mobile antennas can cause issues but if having these issues at several locations then highly unlikely, if alarm is actually not turning off then issue with alarm receiver/antenna or alarm electronic mainbrain is possible.

Obviously just using the key on the drivers door to test the locking & unlocking for a few times will help to diagnose what at fault too as if work all the time via the key then likely the initial driver door locking motor at fault.

Transponder is normally term associated to the chip with the key that disarms the immobilizer via proximity to a sensor near the ignition barrel. if doors are locking then unlocking when pressed I would be checking basics of central locking function first & if on the basic standard alarm the fob is purely remote central locking in reality with a separate transponder chip that purely works with immobiliser.

M30/M20 alarm has a reset procedure which might be worth looking into & I suspect details on this are in a thread already if need.

Hi again. Not sure how much of that I followed. There is no alarm, both keys are in and out, I.e. they sometimes don't work, but both have new batteries. Not sure what antennas might cause this problem. I use the word transponder cos the garage did! So what does the key talk to that translates the radio signal to a command to lock or unlock the doors. Whatever that is might be the problem?

[Mr B]

If you have just the standard basic subaru system (your comments sound as if you do) you have just remote central locking & also a immobilizer that has a coded pairing chip built into the key & this pairing immobilizer chip in the key is the transponder.

I would also be dubious of your mechanics electrical system technical ability as seems to be using technical buzz words with little knowledge of what they actually are & simple looking faults like you have here can waste big money in the wrong hands.

I would suggest you make 100% sure you also actually do not have the subaru security upgrade sigma alarm (mainly as fault finding on Sigma is a different ball game) as many owners do & never know till have faults that need fixing, basically if you have two small pod sensors on the windscreen d-piller trims, a bonnet switch on a big black bracket mounted behind the securing bolts for the windscreen washer bottle & a small keypad in the flip down coin box located by drivers right knee then you have a Sigma Subaru security upgrade fitted.

Basic remote central locking has the receiver control unit that stores the paired key fobs, receives the fob signals & sends switching voltage signal to the central door locking circuit. The Sigma systems control on central locking is more complex & incorporates dead locking.

I have never replaced a central locking receiver control unit in 15 years+ they been in use on Subarus, it is the most unlikely part to of failed but indeed is still possible, almost all faults I have had on Subarus central locking have been down to the motor & switching related to the drivers door when all doors are effected.

First thing to do is stop using the fob buttons & just use the key to manually lock & unlock the car in you daily use & see if problems still arise & if does it 99% likely not related to remote locking controller & even if doesn't show the fault  still needs the door side of locking reviewed first before spending your cash on expensive parts.

Sorry if seems bit long winded but hard to help much without a long reply & I know all too well a lot of money can be wasted on these type of faults through bad diagnosis & at times can be hard to pinpoint even when a good technician is on the job so worth approaching your repair route with extra care & giving very good details of all fault symptoms, this can make a huge difference to repair costs as many times if a customer has given me very accurate details & answers a few points well I almost know likely cause of faults before even investigating myself & this can save a huge amount of time thus money too ...

[Tom Crabbe]

I won't have time now, but a major investigation will now take place. I will probably revert with further info. Thanks for all the v. useful help.

[Jay762]

Tom feel free to take photos as it may help identify what you have / dont have - ie door pillars / A frames, key fobs etc

[Mr B]

A lot of the All Weather Foresters had the Sigma Security upgrades as it was quite often a sales throw in to close the deal.

Sigmas are very good but faults can be a little more odd/erratic & hard to diagnose.