2002 WRX won't start :(
 

Started with battery problems, the alarm started going off while I was away working, wife rang me and she changed the battery in the remote. She managed to turn the alarm off then locked it and it wouldn't unlock. I ordered a new battery, changed out the one with 1.5v left in it.

The key unlocked the car just fine but the bloody thing won't start. After a LOT of googling and looking around here I've found a few things to check, it doesn't even turn over, but the clock and stereo go off as if it's going to start.

I've checked the solenoid whilst trying to start it and it's not getting the 12v it needs, 12v on the motor though. I've cleaned the earth points, not so much fun getting the TMIC off.

I'm properly struggling to find the relays for the starter, even though I've got the manual, anyone know which one(s) it is?

Could be the battery (the main one, not remote. - 12v...)

Can you stick a voltmeter across the battery as you're cranking (or not, as it were)?

Just got a new battery for it, I'll put the meter across the battery and try it, is it to see if I get a drop? Meaning the starter is trying to draw something?

Is the immobiliser stuck on? Could be the case if the key battery ran out for too long and has lost its memory.

If you've got the manual you will see that the wiring between the ignition switch "start" (ST) position and the starter motor solenoid has no other OEM relays.

http://clarkdh.net23.net/NTL/Ign%20switch.JPG

http://clarkdh.net23.net/NTL/MY01Impreza%20start.JPG

However, this is one of the circuits used by the UK retrofitted Sigma alarm for immobilisation so at some point on it's routing an alarm relay will have been spliced in. Looks like the problem is with the alarm.

Damnit, I thought it might have been the alarm, u recoded the keys, which got the second key that came with it opening the doors but I haven't been able to find anything about the immobiliser. I thought it might have been a clutch safety switch so I bridged the brake switch because I am a muppet, then wondered why the brake lights were always on.

I'm planning to find the clutch switch but I honestly don't remember having to depress the clutch to start it

The early UK models don't have a clutch switch

That explains why I couldn't find it, I thought if the immobiliser was not playing it would crank but not start

Can you hear the fuel pump spinning up when you turn on the ignition (before cranking)?

It does Mark, everything I'm expecting to happen does, apart from the engine cranking

If the pump primes (another immobiliser circuit) why not try applying a direct battery feed to the starter motor solenoid terminal (ignition key in normal running position).

If starter engages and engine continues to run then can assume that the relevant relay in the sigma alarm box has failed/stuck/ whatever.

Good shout, I'll try that after work today! Kind of worrying applying the 12v to there, hand in the engine compartment and all that!

Ran 12v to the solenoid from the battery and its started and ran just fine, it logged a P0335 (crank sensor), cleared that and started it again, it's gone now. Now what? Still can't find anything that helps me find out which relay is what :(

You have, most likely, confirmed that a relay/circuit is stuck/ failed on the Sigma alarm control unit PCB.

The PCB has (at least) 4 relays on it, two for the immobiliser circuits and two to operate the LH & RH indicators
Where that box is could be under the dash near the steering column or behind the glovebox
With it's protective case.
https://www.scoobynet.com/attachment...2&d=1501171638

Without
https://i.ebayimg.com/images/g/9oEAA...r1E/s-l640.jpg

Thanks Don, guess I'll be googling how to take that apart without it becoming a paperweight!

https://cimg7.ibsrv.net/gimg/www.sco...732ceb69af.jpg
found the alarm ECU, its behind the glovebox. im trying to find the interrupt relay so I can test it, cant bloody find it! I thought it was going to be where i took this pic but neither of those have the 6 pin connector I'm looking for on it.

Can I take the alarm ECU out without bricking it? As in, undo the bolts and get it out some so I can test the outputs?

It would be useful if you were looking at the UK/European Impreza wiring diagrams not the US version which comes with/without Subaru Security system.

Wiring for a MY02 WRX would be covered by the MY01 manual (a supplement was added for the arrival of the STI in MY02)

Early UK Imprezas are equipped with a Sigma M30 security system (alarm plus two immobiliser circuits) to meet Thatcham category 1 as the OEM immobilizer is only Category 2

MY02 US Impreza (If you have a copy of this manual you will notice there are no LHD/RHD distinctions)
http://clarkdh.net23.net/NTL/MY02%20...eza%20elec.JPG


Yes you can remove the alarm box, have done so myself in the past when the indicator relays have stuck. Make sure you have the PIN plus working fobs just in case they are needed.

This is the UK/European MY01 manual
http://ken-gilbert.com/01-impreza-service-manuals

Thanks very much Don, looks like I'm looking for a relay that doesn't exist! Thought I was going mental, so can I just pull the alarm Control Unit out and take it all the way apart without worrying about pressure switches or hair switches that turn it into a brick? I'm pretty comfortable with electronics I used to fix old radios.

As above

Yep sorry wasn't sure if I could take it apart!

OK I have the thing out, and none of the pinouts I've been able to find seem to have a clue which wire is the one on the end of the possibly dodgy relay so I can bridge it and see if it's the fault. Anyone know which pin is the signal out for the starter motor circuit?

Have I gone in too deep? What other symptoms would indicate that the start signal wasn't being produced? Just checked that, it's fine.

Sorted it! Did something to bypass the ignition part, bleeding thing starts with the key now!

Thanks all for the help, went down a few rabbit holes on this one :)

Just need to put back all the dash I ripped out, bleeed the brakes, change the timing belt...

good result - well done :)