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Discussion Starter #1
Hi all. My old work horse refused to start one morning. Immo shows green after entering the PIN code. Thought it was the fuel pump but it works fine. ECU just don't control fuel nor ignition relays. Tried another ECU, didn't help..... Groundings checked. All help highly appreciated!
 

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You cant try another ecu it is matched to your keypad !

If keypad going green its not the immobiliser check all fuses in under bonnet fusebox you are missing a power feed also check the isolator button under bonnet
 

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Discussion Starter #3
Thanks for the fast reply! I thought it has to be an ECU issue so ordered one from the eBay with same product numbers. Of course there was no PIN code for that particular unit along the shipment. By using the owner's manual I could change my own PIN code to that ECU though. Maybe it was resetted somehow.....? Anyway keypad shows green and the red light turns off in the dash with that ECU also.

I have opened the lid from the ECU and measured all the groundings and operational voltages from the pins of the connector inside the box. Also checked all the "field" components You can deduce something with resistance value by using Haynes schematics. Tested also the fuel pump control circuit by a jumper in the ECU connector. Isolator button mentioned is in the series of the fuel pump and tested that way.

Just remembered there's still a blown fuse for the headlight washer I have ignored. There can't be anything crucial behind that one, haven't used washers for years... Anyway has to check that also
 

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That does not seem right the wrong ecu should show a red light as the unlock command is being sent to the wrong ecu and would come back as no can do :)

People always blame ecu for issues but the ecu is rarely the real problem its nearly always wiring related.
 

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Before you go to all this trouble with an ECU,that reliable406 quite rightly says is very rarely the cause of a problem.Fit a new multi fuction relay,its in the box with the ECU.
My wife's old 16v 406 would often just refuse to start,tried everything,I was advised by a Peugeot expert to replace the relay and bingo its started on the button ever since.
One tip,get a genuine dealer one,not a cheap copy.
 

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Discussion Starter #6
Thanks for the replies. You're both right. Also an authorised dealer said there haven't been any ecu issues with these motors. The multi function relay was the first component to check. It works well. ECU just refuses to control it... How is this first era immo made? It consists of the brilliant keypad, red led on the dash and an EEPROM inside the ECU? Haynes do not show any modules....
 

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The keypad sends an unlock signal to the ecu and if it matches the ecu unlocks its that simple !!

Once unlocked you can actually unplug the keypad and the ecu remains unlocked !!

All the immobiliser gubbins are in the keypad.
 

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The keypad sends an unlock signal to the ecu and if it matches the ecu unlocks its that simple !!

Once unlocked you can actually unplug the keypad and the ecu remains unlocked !!

All the immobiliser gubbins are in the keypad.
We did that with our key pad,unplugged it when the car was running and never used the stupid thing for years.
By the way,have you checked the wires going to the key pad multi plug? they can break.
 

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Discussion Starter #9
Ok. Just what I thought. The keypad was removed when this non-starting started :) I've read the immo still can get activated after a couple of years. Luckily this motor is no longer in every day traffic but it would be a shame to waste a decent motor :))
 

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HI...my son had a laguna with a card/button start and after a non start while on holliday he called the rac who after fitting a new battery (apparently french batterys are crap)diagnosed ecu fault.Recoverd the vehicle to me and checked enrgising wire to starter motor while pressing button.....replaced starter ...all ok......just a thought...good luck
 

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You are now saying the keypad was not connected before you had problems and you have plugged it in trying to fix the problem is this right ?

If so that was a bad move as you have now added 1 more potential reason to the non start coctail :)

Has the battery been out prior to non start as this can reactivate the locking sometimes ?
 

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Discussion Starter #12
Yes to all, sir :) It's a summer time vehicle. Battery disconnected in the wintertime. But worked very well for a month this summer.
 

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Discussion Starter #13
My hobby406 still refuses to co-operate :) Last autumn we spent some quality time together though. I tried with an ECU having IMMO deactivated. No progress. No spark, no fuel pump control. PP2000 shows no fault codes. Ignition switch checked. All voltages and groundings at the ECU area ok when starting. Anyone got a clue what else than IMMO could cause ECU not to control the fuel pump/spark....?

406 petrol 1.8 16V -96
 
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