 | Home > In Car Electronics > Keyfob unlocks, but won’t un-immobilise [Solved: Earth] |
 
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| Ianh Member Since: 17 Sep 2018 Location: Essex Posts: 2028  
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Disconnecting a main / starter battery, or a main / starter battery going very low should not cause the 10AS to loose sync with the Engine ECU. Noting it can cause a brownout issue on the later ALM CHxxxxx versions, but yours being a 2007 puma should be the Green 10AS unit.
The fact that your fob operates the central locking shows it is synchronised with the 10AS. When you say you can’t turn the car on, what exactly is happening ? Is the engine cranking but not starting, or not cranking at all ? I.e starter not turning etc. I’m more inclined to think you have a bad earth connection, a blown fuse or potentially relay issue. Even not having the battery terminals not pushed down and well clamped will prevent starting. |
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31st Mar 2024 4:32pm |
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| bitcoin Member Since: 21 Mar 2024 Location: UK Posts: 10  
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Thanks for the reply here
It’s a 2009 2.4 if that makes any difference. I’m not getting any cranking at all. So fob unlock. Key in the ignition. Move to position 2. Dash shows engine check light, battery light, and the glow plug light for a second. (The third relay under the drivers seat clicks at this time. I think this is the glow plugs?) Then I twist the key to try and crank but literally nothing happens. I do feel a slight click in the second relay under the driver’s seat at this point. Sometimes… and I mean maybe twice in trying this many many times I hear a slight click somewhere below the car. But usually just nothing. (I don’t feel or hear anything on the first relay under the seat). I have checked the blue fuses under there and are good. The earth connection to the transfer box was somewhat corroded (aluminium/steel) but I’ve put it back in very tight and would be surprised if it’s not getting any electrical flow? The battery has remained untouched throughout me doing the works and the car started fine prior to works commencing. I have had it on a charger for a day or so now though as I noticed when I was locking and unlocking the car with the fob (to get tools out the back etc) that the indicator lights stopped flashing - which I assumed to be due to low main battery voltage. (Could be wrong here) Main battery is showing 12.45 last time I checked and is on trickle charge |
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31st Mar 2024 4:41pm |
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| custom90 Member Since: 21 Jan 2010 Location: South West, England. Posts: 20436
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Battery clamps might be loose, either of them.
Press the fob rapidly to sync it about 5 times until dash alarm light flashes fast. When it slows to a normal speed you can lock or unlock it like normal. If you have checked all the main battery clamps, live and ground connections, physically and electrically. Then the starter may have gone. But check everything else first. $W33T $0U7H3RN $UG4R 🇬🇧🏴🏴🏴🇮🇪🇺🇸⛽️🛢️⚙️🧰💪 |
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31st Mar 2024 5:03pm |
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| Ianh Member Since: 17 Sep 2018 Location: Essex Posts: 2028
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May be a red herring, but when did you last change your fob battery ? It could be a strange coincidence but a low fob battery could be the issue, so fit a new quality Panasonic or Varta CR2032 battery, sync the fob as before so central locking works. Make sure you have only one fob with you and it’s close to the ignition and then try to start the vehicle.
I’m still inclined to think it’s an earth or fuse issue but for a couple of pounds it’s worth a try. Noting the 10AS does have a facility to tell you the fob battery is low , and that does include the indicators not blinking as normal when using the fob to central lock/ unlock. Ps. Another indicator that the fob battery is low is when the engine is running the red alarm dash light stays on (not blinking) when engine is running. Obviously you can’t start engine so not helpful now but good to know for the future. PPS, if you have another good fob you could try that as a test. Alternatively you could have blown one of the 10AS fuses. Looking at the fuse box diagrams I can see there are two in the under seat fuse box, ID 10 (20A), ID 11 (15A), and one in the under dash fuse box , ID 16 (fuse 8 , 10A). https://www.lrworkshop.com/electrics/defen...nd-headers |
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31st Mar 2024 5:27pm |
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| bitcoin Member Since: 21 Mar 2024 Location: UK Posts: 10
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I have already tried changing the fob battery unfortunately. Unlocked car. Pulled battery. Held buttons for 10 seconds. New battery in. Pressed lock 4 times (first three times nothing happened, then on fourth it locked) then fob is working as usual. Still no cranking though.
I have also just removed, wire brushed and replaced the earth cable/bolt from the right side of the transfer case. Again, to no avail and still no crank. Battery is sitting at 12.88v Battery connections seem firm and I haven’t touched them during any of the works - and it cranked just fine before. I only have the single fob unfortunately. Perhaps next step is checking the fuses you kindly listed above. A real head scratcher - would removing/replacing the earth on the tbox have the ability to blow a 10AS fuse? |
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31st Mar 2024 6:45pm |
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| custom90 Member Since: 21 Jan 2010 Location: South West, England. Posts: 20436
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If you have a multimeter check the mega fuse is in-tact on the live battery post with a continuity check or a voltage check on the starter itself, that way you’ll know there is voltage at the starter and if there is the mega fuse is in-tact.
Are you sure the ground cable isn’t damaged anywhere? It’s usually the most simple things that cause these issues. $W33T $0U7H3RN $UG4R 🇬🇧🏴🏴🏴🇮🇪🇺🇸⛽️🛢️⚙️🧰💪 |
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31st Mar 2024 7:00pm |
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| Siwynne Member Since: 04 Nov 2016 Location: West lancs Posts: 578 
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Disconnect the battery at the terminals and reconnect as per workshop manual. You may have confused things by just effectively removing the negative by playing with the earth strap. I can’t remember the sequence without looking but it is important. https://www.defender2.net/forum/post702214.html
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31st Mar 2024 9:19pm |
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| jst Member Since: 14 Jan 2008 Location: Taunton Posts: 8050 
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When you say nothing when ign turned to pos3 to crank you mean no crank and dash lights stay on? Or nothing in that it all goes off.
What's voltage pos bat to gbox casing? Try 12v to starter relY on sm. Does it crank and go or crank crank crank or not cank at all? Cheers James 110 2012 XS Utility 130 2011 M57 bespoke Camper 90 2010 Hardtop 90 M57 1988 Hardtop |
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31st Mar 2024 10:01pm |
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| bitcoin Member Since: 21 Mar 2024 Location: UK Posts: 10
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Okay I’ll try disconnecting and reconnecting the main battery to see if that helps
I think the sequence is: key in ignition. Ignition to position 2. Ignition to position 0. Then disconnect battery terminal within 15 seconds of moving to position 0. Fingers crossed - As for what exactly happens when in position 3 to crank: dash lights all stay exactly the same. The doubledin radio (installed by prev owner) screen turns black and the led illuminator on the cigarette lighter turns off. Then when back in position 2 the radio screen and cig lighter led turn back on. (The radio screen is not restarted. Just the screen seems to turn off then on again back to where it left off) |
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1st Apr 2024 7:33am |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17435 
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The radio screen going black suggests it could be that the starter motor is trying but is unable to turn (heavy current draw and no back-EMF pulling the battery voltage down).
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1st Apr 2024 8:14am |
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| bitcoin Member Since: 21 Mar 2024 Location: UK Posts: 10
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I see
Any way to better test this / find a resolution? (There is zero crank, like not even an attempt) I’m also wondering how this could have been caused (if this is the issue) by removing and reinstalling the transfer case. This case has a single earth going to it along with some road speed and high/low detector circuits. Could the starter motor be physically jammed in any way somehow? Tightening up the output shaft bolts did turn over the gearbox and engine a bit whilst in 6th gear but I don’t know how that could have caused a mechanical lock |
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1st Apr 2024 8:20am |
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| bitcoin Member Since: 21 Mar 2024 Location: UK Posts: 10
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Just disconnected the battery negative terminal to no avail
- unlocked with fob - key in ignition - move to position 2 - move to position 0 - remove neg terminal within 15 seconds - cleaned up terminal and refitted tight with impact socket I can’t be sure, but I feel like I might have accidentally very slightly removed the neg terminal before doing the key ignition thing whilst undoing the nut. Not 100% sure, but if I did lose connection for a split second, the alarm did not go off Either way, battery terminal is reconnected, key fob syncs by pressing buttons 4 times and all is the same as it was before - except the radio now asks what language to put it in lol No crank continues… |
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1st Apr 2024 9:43am |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17435
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There is good advice already in this thread.
it is most likely though not guaranteed that if a fault developed while you were working on the vehicle it has something to do with what you were doing. There is no connection at all between the immobiliser and the transfer box wiring so it is inherently unlikely though not impossible that the immobiliser is on the blink. You may (should) have disconnected the battery when replacing the transfer box (you haven't said if you did or not), and on rare occasions this can initiate faults. It is relatively unlikely though. You will definitely have disconnected the earth connection from the chassis to the transfer box however, and failure to reconnect this correctly, or some other fault connected with this lead will cause the symptoms you describe. It is worth remembering that the battery negative terminal is connected to a lead which runs firstly to the chassis and then on the the transfer box. This lead is the only one that connects the (rubber-mounted) engine, gearbox, and driveline to the chassis, and if it is broken, disconnected, or has a high impedance/resistance electrical systems on the engine will not work. So the starter won't crank, and if the car was tow started the alternator won't be able to charge (in practice what tends to happen is the handbrake cable - which is connected at both ends to metal - catches fire as it tries to provide an earth path for the 100-Amp alternator output). So the first check should be that this connecting is sound. (If the lead from the battery to the chassis is OK but the lead from the chassis to the transfer box is not connected, all the other electrical systems such as lights, radio, immobiliser, etc., will work; only those circuits which rely on the engine-to-chassis lead will fail, so starter and charging). If you have a multimeter, check there there is very low resistance between the transfer box and the chassis. If you don't have a meter (which will make diagnosing problems a lot harder) try connecting a jump lead from the transfer box to the chassis, or from the transfer box to the neg terminal on the battery and see if the starter then cranks. if it does you have found the problem, if it doesn't then you will need a multimeter or 12V test lamp. If you have ruled out the chassis-to-driveline earth lead, then I suggest the following:- 1. Check that you have a constant 12V supply to the terminal on the starter motor. Do do this connect a voltmeter or test lamp between the negative battery terminal and the lug on the starter solenoid. If you don't have 12V, check the lead, the megafuse, and the security of the positive battery terminal clamp. If you do have 12V on the lug, check that you have 12V between the lug and the body of the starter motor. If you don't, check the earth lead (again) and check the security of the negative terminal clamp. If all these checks pass then you have power to the starter, so it is time to look elsewhere. 2. The next area to check is starter energisation circuitry. I would suggest that the next sensible step is to bypass the starter relay (R102) under the driver's seat. If you bridge terminals 30 and 87 (the numbering follows the standard for a relay) then the starter should energise and crank the engine. Ideally do this carefully with a suitable switch, it is a high current circuit (fused at 60A) and there is potential for personal injury. If the engine cranks then there is no fault with the starter and the problem is with the circuitry that energises the relay or the relay itself. If the starter does not crank then either the lead from the relay to the solenoid is broken/disconnected (listen for the solenoid clicking - if it does the lead is OK) or the starter is seized or faulty, or the engine is seized or locked solid. 3. If the starter cranks during step 2 above, check that 12V appears between terminal 86 in the starter relay socket and ground when the key is turned to the 'crank' position. If it doesn't, then you have a fault with the key switch circuitry, most probably the switch itself. If you do, then the problem is either the ECM or the immobiliser. If this is the case diagnosis becomes quite a lot harder, so I suggest getting to this point and posting how you get on. I'm sorry to say that the TDCi Defender is notorious for being a right pain in the whatnot when it refuses to start, mainly because the immobiliser is not very robust. Patient troubleshooting in a logical sequence is usually the quickest solution, but it is important to be methodical. |
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1st Apr 2024 10:13am |
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| bitcoin Member Since: 21 Mar 2024 Location: UK Posts: 10
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Sorry @blackwolf I have now solved this issue! Thankyou so much for your input and suggestions
I had totally forgotten about the huge earth cable on the left side of the transfer case. I had ‘definitely reconnected the earth’ to the right side. But in doing so, in my mind I had ‘checked off’ the ‘reconnect earth’ task! I had also stowed this left hand cable well out of the way to give me plenty of room to put things back together and so I also hadn’t spotted a loose cable dangling around needing a home! So all in all, everything is working just fine again and at least I’ve been on a bit of an electrical journey and checked a few other areas to also be in good condition! Thankyou! |
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2nd Apr 2024 8:33pm |
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