Thread: Puma Defender

It does sound more likely now that the 10AS is at fault by not sending a mobilization signal to the EMS. Here is a post I did on another forum explaining the passive immobilizer and how it works, also note that the immobilizer inhibits the starter and injector circuits until a valid mobilization code is received from the 10AS. Also the fault on this defender turned out to be corroded pins on the 10AS due to water ingress from a leaking windscreen. The corrosion on the pins stopped the mobilization signal from being sent to the EMS via the IC causing the EMS to think no code was sent, meaning the starter and injector circuits stayed inhibited. Problem was resolved with unplugging the two plugs and a liberal coating of contact cleaner to clear the corrosion. All works well now.

Defender2 - View topic - Puma Cuts Out – Why?

Originally Posted by Lorryman100 on Defender2.net

The 10AS unit doesn't stop the engine, the EMS does acting on information received from the 10AS unit.

The passive immobiliser works by switching on the immobiliser after a set time once the key/fob is removed. It detects this by using the transceiver coil on the ignition barrel to detect the key/fob. If there is a problem with the passive immobiliser through a fault with the transceiver coil or fob then it will act as if the key is removed by initiating the immobiliser which will stop the engine by inhibiting the starter and fuel injector circuits.

From the Puma workshop manual:



The pulsed feed from the 10AS module causes the magnetic field created by the transceiver coil to collapse and restore. The fluctuating magnetic field activates the fob (remote RF handset) to transmit a mobilization code to the 10AS module. The 10AS module receives the fob mobilization code via its antenna. This fob code is compared to a value in the 10AS memory. If the codes match, the 10AS module provides a mobilization signal to the instrument cluster. The instrument cluster acts as a gateway, converting the signal transmitted from the 10AS module into a signal that is recognizable by the ECM. So when the engine is running with a faulty passive immobiliser and it activates it will immobilise the engine by inhibiting the injectors causing the engine to stop.

@austastar, the reason for that procedure listed in the handbook is to drain any stored capacitance in the electric circuit. A bit of a faff procedure when disconnecting the battery and leaving it for 10 mins does the same job. A point to note as well is that if anyone has any issues with the alarm unit in that the led flashes continuously or the fobs suddenly don't work, then disconnect the battery to allow a hard reset of the 10AS unit. When the battery is reconnected the 10as reverts back to its last stored write settings which does not include any tamper/alarm activation issues.

HTH Brian.

Hi every one, I thought I would let every one know what happen at the dealers. Well the Defender went to City Land Rover in Melbourne on Tuesday, took them a while to find what was wrong. when they did, they said that it was the ignition fuse. It wasn't blowen but just dirty contacts, they pulled it out and replaced and the car started. All that drama for such a small thing, that is without the car for four long days.

Anyway a Big thanks to everyone who helped
Geoff.

Nice that it was something simple and easy to fix, but frustrating that it took so long to find it - a useful tip for people in a similar pickle. I'm filing this one away in the "Before you call the NRMA/ Land Rover Assist...check this" folder in my brain, so thanks for sharing Geoff.

I had a similarly frustraing issue the other month. 08 Puma, key fobs stopped working. Thought the batteries in them were gone and didn't want alarm issues by trying the door with key only (I wasn't aware that I could do this) as at the time I didn't have the security code.

Turned out to be just the car battery connections - they weren't tight despite being attached to the terminals and the bloke who came out did the diagnostic check and said they have to be on really firmly. I'd diconnected them the day before and not tightened them up enough prior to driving home.

Understanding car electrics is more difficult for me than understanding girlfriends.