Immobiliser fault? This Meggy is heading for the scrappy!

[triumph2.5man]

After many years of battling with our 1.5dci 80bhp 2003 110k miles, I have yet to concede defeat! However, my back is now against the wall and the car is probably heading to the scrappy.
After the usual raft of "stop-check injection" messages (seen 'em all before!) the car failed and had to be recovered to my home (and not for the first time but probably the last). I identified two leaking injectors and got the car running OK with several test drives. What happened next took me completely by surprise. The error messages stopped but the car would not start. After much repeated checking it appears that the UCH is not unlocking the injection computer. How do I know this? The injectors are not pulsing and the flow actuator solenoid on the high pressure pump will not open. So there is no diesel at the injectors. There is fuel at the pump inlet and removing the fuel temp sensor, fuel does pump out so clearly the pump is working OK and air locks are ruled out. The impedance of the flow solenoid is within stated parameters.
The first thing to check for is always the dreaded water ingress to the UCH but this car has none. I have checked every single fuse and relay on the car and all is in order. I removed the PCB from the UCH and it is in spotless condition. No other electrical faults are in evidence.
I checked everywhere for broken wires or bad connections and nothing found. Lots of wires to check! This has been going on for a week with no light at the end of the tunnel. During that week, the car has started once only - out of the blue. I took it for a 10 mile run and after switching off, it refused to start again! Daughter, who drives the car, is sick of it and does not want it back ever. When it failed last week, the police had to tow the wretched thing off the road as it stopped on a corner on a busy road. Luvverly - not!
The presence of four young girls in the back with darkness descending and a long wait for recovery added to the misery. Not many Megane fans in my family now!

I don't have access to diagnostics but i doubt such an obscure fault would be logged. The error messages on the display (of which there were many) have stopped completely which is ominous. The little handheld code reader from ebay was useless as it could not access the UCH or injection computer. A laptop with ELM327 interface was equally useless for teh same reason. I would have access to an expensive code reader (in fact several) but as I cannot move the car, I cannot get to the instruments! Catch 22. Stuck!

Just to sum up, the keycard is recognised and the starter turns over (but only for about 3 or 4 seconds), then stops. Second keycard is the same. Immobiliser light indicates as it should. I suspect a fault with either the UCH or the injection computer or both in which case, goodnight Irene, sorry, Megane! The car has very little value now.

This is complex but if anybody would like to make any comments I will be pleased. Keep them sensible and decent please....and yes I did check the crank and cam sensors!

Mike (aged 72 with many years experience as a mechanic but no longer a Triumph 2.5 owner....!)

[triumph2.5man]

Here is an update after much work today. The injection computer sends a signal of about 3.5 volts to the flow actuator solenoid which then opens and releases fuel to the rail (or circle in this case). When full pressure is reached, the rail pressure sensor sends a signal to the injeciion computer and the injectors start pulsing.Capisce?

In my case the solenoid is not receiving the 3.5 volts.
I wondered if the solenoid could be stuck shut but having removed it, checked it and applied voltage to the terminals it functions perfectly. it was fairly easy to remove and I noted that it contained an internal filter which was clean - no fuel pump bearing bits in there! The spring pressure on the plunger is adjustable via a brass plug on the back.

I did manage this afternoon to get the car to start. Faint! At the time I had a digital meter on the solenoid feed wires while somebody else operated the starter button. Initially there was no reading but after about 2 seconds, voltage appeared and the engine started and ran well and the voltage remained stable at 3.66v. I stopped it and it started again but only just. Took for a test drive, turned off and it has failed to start since! I suspect a bad contact (or "dry joint") in the injection computer and the impedance of the digital meter caused the current to flow. An obscure fault which could prove impossible to diagnose!

Mike

[tanto12]

I don't know where you are but could put you location and ask if there is anybody on forum close to your location who can do diagnostics for you

[triumph2.5man]

Another update! The car refuses to start at all. The chaps at the local Renault workshop are helpful but could give no idea of the fault short of taking it for a (expensive) diagnostic on CLIP. Not only can I not get it there but the car is now on a SORN. Daughter got so sick of it she bought another car! - a Megane 3 dci. Oh no, not again!

I had the chance to have diagnosis on a Snap-on machine but the only faults logged are old injector ones. Good as this machine is, it can never compare to CLIP.
The present fault is not logging any DTCs at all. I did notice one thing - the battery goes flat every evening. I found that, with the ignition off, the electrics are consuming around 3 amps. Judicious use of an ammeter traced the current back to the UCH. The UCH has 5 plugs and removing a certain one, reduced the current. I examined the PCB but no sign of any damage (nor did I expect to find any.). The PCB has 5 relays soldered on and any one of those could have failed. I suspect the UCH has developed a fault and is perhaps not releasing the immoboliser. This is just conjecture on my part but everything else on the car seems to work. The car, despite its smart appearance, has no value and replacing the UCH is out of the question

Nearing the end of the road and running out of patience....looks as if the beast has beaten me!
Mike

[VroomVroomClonk]

Hi Mike,

Where in the country are you please? I'm in Suffolk and I have a CLIP which you are welcome to borrow if you are nearby? Unfortunately I can't really post it to you as the software it needs is loaded on my daughter's laptop, and she wouldn't be too happy to see that go!

[triumph2.5man]

Hello again! I do wish I knew your name! I live in north Suffolk "the most easterly point of the British Isles" - soccer team play in blue - not the "tractor boys" but the "trawler boys"!
Sorry for delay in replying - been away for a week.
Before I take up your generous offer of CLIP, I have another iron up my sleeve but I am thinking if the UCH is knackered, then nothing will be able to communicate with it.
I might take up your offer, so watch this space! Incidentally where did you get CLIP from? Or would that be telling? I am thinking of buying a half-decent code reader but with thousands to choose from on ebay (all claiming to be as good as main dealer system!), it is hard to choose. The last one I bought was useless and unable to communicate with the injection computer. I look after the rest of the family cars (all old, high mileage CR diesels) so ideally I would like an instrument to cover all models and not just Renault. The big question I posed on this forum a few years ago (when there were many more bods responding), was never answered. OBD2 applied from 2004 with diesels. Is my 2002/2003 model OBD2 or not? ELM327 interface could not communicate with the injection computer either.
Regards, Mike (PS your little trick with the brake pedal switch worked a treat and was a permanent cure. Pity the same cannot be said about the rest of the car!!)

[VroomVroomClonk]

Hi Mike,

Sorry for the slow reply, I've just been away for a week now as well.

I've sent you a Private Message with some more info. Please let me know if you'd like me bring my CLIP and see if we can work out what's wrong with your engine.

[triumph2.5man]

Thanks for that. Have replied to your PM. is anybody else actually reading this....? Or interested?
I had access to a good Snap-on machine last week. Loads of DTCs in there as expected, most did not surprise me but two did. One related to the "switching and protection unit" (UCP to Renault) and another related to the "after ignition relay". (After ignition means with the ignition on).Snap-on machines do not give P codes.
Codes were all cleared and attempts made to start the car - failed. The point is no further codes were logged, confirming what I thought, that there is no communication at some point between UCH, UCP and injection computer.
This car has 4 relays that can be changed (2 under the UCP, 2 above internal fusebox. These are easy to test and all found to be perfect. However the UCP has 7 soldered-in relays and possibly five more. Next step is to consider changing the UCP and transferring the external multiplex unit to a replacement board to save the programming. Watch this space!
luckily I am retired so time is costing me nowt! Luckily also that I like a challenge....
Mike

[taffyhl]

Mike,

Reading with interest but it's way over my head so can't offer any advice I'm afraid!

Fingers crossed you solve it soon. By now I would have given up and crushed it!

Hywel

[gareyt]

I love your posts Mike, Please keep us informed of your progress its always great to read how people fix there megane's and the processes they go through.

Keep at it, you could be nearly there and you just don't know it yet.

[triumph2.5man]

Thanks taffy and Garey. Nice to know that at least two members are reading the rubbish I write!
Update. I purchased from my local scrappy, a UCP, cost me a tenner. Many Meganes to choose from, all in lovely condition (just like ours!). Before swapping components on the board, I decided to see what would happen if I fitted it untouched. Although the car would still not start, the immobiliser and the steeringlock disengaged and the starter whirred away merrily. This confirmed what I wondered, namely that the UCP is NOT coded to the car. The UCH is and it is the UCH that controls the immobiliser and clearly there is nowt wrong with that. Everything on this car works except the fuel injection and all the signs point now to a fault with the injection computer (the DCU - "diesel control unit" - all these acronyms!). Not only is the DCU coded to the car, it is imprinted with the VIN FOR LIFE! No possibility fitting a used one of those. And as for buying a new replacement, no chance!
Sadly the car has no future whatever the outcome and I am continuing with it only as a challenge to find the problem and perhaps help somebody else. This is not going down well with my family as the darned thing is in the way on the driveway!
Just one more trick to try......
Mike

[MeganeMule]

Iam also following avidly Surely buy a DCU from scrappys and get someone from on here with a clip to code it ?

[triumph2.5man]

If only it were that easy! Renault manual (not Haynes) makes it quite clear that DCUs are coded for life with the VIN. it cannot be deleted or amended. A DCU will never work with another car and cannot be made to! The chip that is coded is not an EEPROM.
Monsewer Renault has us over a barrel I'm afraid! I expect other makes are the same though.
M.

[gareyt]

I took all the electrical brain boxes out of my car once, I opened one up, nearly had a heart attack and then put it all back together with crossed fingers that it would be ok.

I didn't know about this DCU. It sounds like this is the end now. If this thing cant be replaced or repaired then what can be done?

[petepete]

My megane is 2008...

In the past when removing fuses from glove compartment I discovered one particular one once removed allowed me to start and run my car from the start button without using the key card...

with your problems I would use this as a fix..

lets just say I decided to prevent this possibility on my car as it left me feeling pretty dam insecure , cheers Renault !