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Help needed, 5th gen immobiliser issue

Engine/Gearbox questions and discussion
mr_pea
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Help needed, 5th gen immobiliser issue

Post by mr_pea » Tue May 19, 2020 2:06 pm

Hi all, apologies if this has been asked many times in the past, but can anyone help us out or point us in the right direction please?
Our 5th gen won't start at all due to the immobiliser, it's been temperamental for a while and has now decided that it just won't let us start the car at all (quite frustrating really as just had all the rust cut out and the car resprayed).
What options do we have and where to go to get it fixed other than getting the car to our local honda dealer?
I appreciate that this may not be a good topic for public consumption as I need to know if there is a way of bypassing the standard immobiliser and can then get an aftermarket one fitted.
If anyone can help, it will be greatly appreciated (feel free to pm me if you would prefer).
Thank you, Toby

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Help needed, 5th gen immobiliser issue

Post by wurlycorner » Tue May 19, 2020 2:14 pm

Hi mr pea, good to hear from you on here again :)

A *decent* automotive alarm/immobiliser or electrician should be able to help investigate this, I would have thought?
I'd suggest they'd probably be better than taking it to Honda, tbh (since it's an old car and generally Honda dealers don't have experience in diagnosing pre-full OBD2 compliant stuff these days).

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Help needed, 5th gen immobiliser issue

Post by Scott560 » Tue May 19, 2020 2:15 pm

Few questions:

1) What actually happens, do all the dash lights work and the car just fails to crank when commanded? There is a specific flashing pattern of the immob key light in the dash if the immobiliser is not happy with the proceedings. Its worth confirming it is immobiliser related and not battery/starter/solenoid issue.

2) you say its been temperamental - was that before any of the body work was done?

3) the immobiliser is based on the key and the pickup ring around the ignition barrel. Make sure you don't have anything in the way that can interfere. Other keys, decoration etc. Do you have any other keys to try (except the red one , or the grey one lol).

The ignition switches can wear over time leading to a complete loss of power, but i could imagine it causing trouble during cranking.

Any reason to believe the battery isn't the culprit? If the car has been standing a while whilst body work took place, even if it shows 12v there is no guarantee it can crank.
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mr_pea
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Help needed, 5th gen immobiliser issue

Post by mr_pea » Tue May 19, 2020 4:15 pm

Thanks for the replies in response:
1) immobiliser light flashes, then goes off. All other lights work, but stay on when you turn the key. Engine doesnt crank, doesnt do anything.
2) has been temperamental for a long time before the work was done, just always started eventually (just to add, always started 1st time once it wanted to, not a problem with starter or battery, just seems like immobiliser as seems like no power to anything)
3) tried key with nothing attached, no joy, however, after just asking my wife (her car), she may have tried it with the red key (I'm now not liking your comment about red key!)
Just to add, new battery has been fitted and tried with new battery from other cars as well and still no joy.
Not sure if any of that makes sense

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Help needed, 5th gen immobiliser issue

Post by wurlycorner » Tue May 19, 2020 5:48 pm

mr_pea wrote:
Tue May 19, 2020 4:15 pm
1) immobiliser light flashes, then goes off.
So that in theory, means the immobiliser has recognised the key correctly and will tell the ECM and starter relay to work normally and the fault isn't with the immobiliser.
All other lights work, but stay on when you turn the key. Engine doesnt crank, doesnt do anything.
So this means either a fault in;
The ECM
The Starting System (down-stream of the immobiliser)
The Ignition Switch (the 'start' contacts)
The wiring in those systems.

The starting system has a lot of components to it - depending on what model you have (auto/atts etc adds more complication)

Section 23-195 onwards in the 5g manual is the section you want to look at.
However, I'm not a massive fan of the fault tree on page 23-201 tbh... It's a bit simplistic and immediately jumps into wanting to re-programme keys if the engine doesn't crank - that doesn't take any consideration of there being other faults in the circuit down-stream of the immobiliser (which if this is an intermittent fault, is far more likely - because an electronic system doesn't randomly forget and remember keys, it either has them programmed in or not!).


Edit - tracking back to the starting system (4-4 in the manual) up-stream of the immobiliser is also the starter cut relay.


But yeah, basically this is all pretty basic stuff for a good auto electrician to chase through, with the aid of the manual (or if you're a bit handy yourself with technical stuff).

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Help needed, 5th gen immobiliser issue

Post by Scott560 » Tue May 19, 2020 5:56 pm

If at any point you put the red key in, you have entered a very small world of pain.

The red key is the master key, and puts the immobiliser into learning mode. You use this only when you want to remove keys from the system memory (eg lost a key or it got nicked), or if you want to add some new keys you bought (eg, learn the transponder code of new keys you had cut). Im sure you are aware that the keys have little transponders in the rubber part which transmit unique serial numbers - which of course make up the immobiliser system.

If you put the red key in , and didnt know what you were doing - you've almost certainly wiped the keys that were in the system, hence not starting now. I haven't read the section in the manual (no red key for me :( ), but its a relatively simple process to learn them back in. I suspect similar is available on youtube. Process is something like:

1) put the red key in, ignition on , immob light may flash to indicate learning mode.
2) put in each black key there after and cycle the power a certain number of times to learn them in.
3) all that is done in a 30 second window or similar, and only those keys are learnt/allowed to start the car. Put red key somewhere safe, not in the car.

Now you know what the red key does, even if you still have a temperamental issue aside - you still need to learn the black keys back in before you have any hope.

If you cant find it on youtube (I suspect its similar for many hondas), i can find the section in the manual more fully.
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Help needed, 5th gen immobiliser issue

Post by wurlycorner » Tue May 19, 2020 6:01 pm

Yeah, but if it's gone into learn mode, you won't have an intermittent not starting problem - it will have forgotten all the black keys and will never work (until re-programmed).

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Help needed, 5th gen immobiliser issue

Post by Scott560 » Tue May 19, 2020 6:26 pm

Is it an automatic by any chance? perhaps the neutral switch is the cause of non starting...
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Help needed, 5th gen immobiliser issue

Post by Scott560 » Tue May 19, 2020 6:29 pm

wurlycorner wrote:
Tue May 19, 2020 6:01 pm
Yeah, but if it's gone into learn mode, you won't have an intermittent not starting problem - it will have forgotten all the black keys and will never work (until re-programmed).
I always now assume there is more than 1 problem after my intermittent cruise issue :lol:

My thinking in this case is that there was an intermittent problem, and in frustration recently the red key might have been used out of curiosity, now leading to the forum post as completely non-startable?

We will find out!
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Help needed, 5th gen immobiliser issue

Post by mr_pea » Tue May 19, 2020 9:09 pm

Thank you all for the replies.
I will try the resyncing of the keys and hopefully that will get it to start.
The other side of it is the intermittent nature of it, in that before it stopped working completely, it would work fine and then not work at all until it felt like it (so I would assume there may be some issue with one part of the immobiliser connections, ring, etc).

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