Technical A Possible Fix for Immobiliser Problems

[Communicator]

I have mentioned my immobiliser problems previously somewhere on forum.

I had several instances of key code failure, but these had only happened while at home, with a cold engine, and not really needing to start the engine.

Last autumn I had a single failure when away from home with a warm engine. Started OK on immediate second attempt.

On checking earlier this year I had a 2 out of 5 or 40% failure rate. Confidence in the vehicle fell off a cliff.

I seriously considered buying and carrying a spare ECU with the code system deleted. However I reasoned that as the problem was marginal, it may be due to surface oxidation of the aerial connector contacts on the code receiver. The signal voltage will be very low at this point, and that there may be no contact
"wetting". (Wetting is a term used to describe the process whereby a higher DC voltage is applied to relay contacts, which would otherwise only have low signal voltages across them. Gold plated contacts used in electronic systems fulfill the same pupose.)

I was aware of some suggestions regarding unplugging and replacing the 8 way connector at the code receiver, but given the low signal levels, I thought the aerial connector to be a more likely cause.

Armed with a contact cleaner aerosol, I removed the steering column lower shroud, unplugged and treated the aerial connector, and while I was in there the 8 way connector which includes the data link to the ECU.

Subsequent testing has resulted in zero failures. Time will be the test, but worth a try if you are stuck with the padlock light on.

 

[bugsymike]

I have mentioned my immobiliser problems previously somewhere on forum.

I had several instances of key code failure, but these had only happened while at home, with a cold engine, and not really needing to start the engine.

Last autumn I had a single failure when away from home with a warm engine. Started OK on immediate second attempt.

On checking earlier this year I had a 2 out of 5 or 40% failure rate. Confidence in the vehicle fell off a cliff.

I seriously considered buying and carrying a spare ECU with the code system deleted. However I reasoned that as the problem was marginal, it may be due to surface oxidation of the aerial connector contacts on the code receiver. The signal voltage will be very low at this point, and that there may be no contact
"wetting". (Wetting is a term used to describe the process whereby a higher DC voltage is applied to relay contacts, which would otherwise only have low signal voltages across them. Gold plated contacts used in electronic systems fulfill the same pupose.)

I was aware of some suggestions regarding unplugging and replacing the 8 way connector at the code receiver, but given the low signal levels, I thought the aerial connector to be a more likely cause.

Armed with a contact cleaner aerosol, I removed the steering column lower shroud, unplugged and treated the aerial connector, and while I was in there the 8 way connector which includes the data link to the ECU.

Subsequent testing has resulted in zero failures. Time will be the test, but worth a try if you are stuck with the padlock light on.

Re the spare ECU, I mentioned elsewhere that I had a Nissan Almera that used to "immobilise " it's self and I played with a Micra Ecu and had wired a extra ECU plug so I could swap over and also carried a Laptop with a Nissan program that could delete the immobilser errors, eventually I traced the fault to a non original Radio.

 

[Communicator]

I have mentioned my immobiliser problems previously somewhere on forum.

I had several instances of key code failure, but these had only happened while at home, with a cold engine, and not really needing to start the engine.

Last autumn I had a single failure when away from home with a warm engine. Started OK on immediate second attempt.

On checking earlier this year I had a 2 out of 5 or 40% failure rate. Confidence in the vehicle fell off a cliff.

I seriously considered buying and carrying a spare ECU with the code system deleted. However I reasoned that as the problem was marginal, it may be due to surface oxidation of the aerial connector contacts on the code receiver. The signal voltage will be very low at this point, and that there may be no contact
"wetting". (Wetting is a term used to describe the process whereby a higher DC voltage is applied to relay contacts, which would otherwise only have low signal voltages across them. Gold plated contacts used in electronic systems fulfill the same pupose.)

I was aware of some suggestions regarding unplugging and replacing the 8 way connector at the code receiver, but given the low signal levels, I thought the aerial connector to be a more likely cause.

Armed with a contact cleaner aerosol, I removed the steering column lower shroud, unplugged and treated the aerial connector, and while I was in there the 8 way connector which includes the data link to the ECU.

Subsequent testing has resulted in zero failures. Time will be the test, but worth a try if you are stuck with the padlock light on.

Still no key code lights.
I am begining to suspect that there may be an inherent weakness in the design of the code receiver. Among with other fields I have some experience with old fashioned electromagetic telephone exchanges. In that now obselete technology it was sound practice to ensure that AC speech signals with a fraction of a volt in magnitude, were accompanied by a much higher DC voltage. This higher DC voltage served to breakdown any oxide film on contacts carrying the speech signal. The DC was simply applied by connecting the two speech carrying wires to the supply +ve & -ve via resistors of 10K Ohms. The resulting 20K across the nominal 600 Ohm speech circuit had negligible effect. I am wondering whether something similar could be done with the key code aerial connections, as this is a discrete connector on the x244. Meanwhile at the first hint of trouble, I will be cleaning contacts.

An alternative would have been the use of gold plated contacts in the aerial circuit. Many members will be aware of the use of gold plated contacts in computer and other applications.