Xantia HDI - ECU Problem

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Xantia HDI - ECU Problem

Post by thorter » 27 Jan 2016, 22:44

After quite a few years without any problem my 2000 year HDI 110 suddenly has an engine management system fault. Can anyone suggest a likely diagnosis or further tests? It ran without issue previous day and is under a car port so dry, though access is awkward.

Symptoms
Ignition on, and immobiliser key light comes on for 3 seconds, then it flashes continuously and the audible warning sounds until ignition off (key not recognised).
Double Ignition Relay and also Preheater relay click rapidly and continuously.
This starts immediately key is turned (ie before key light starts flashing).
It is the first relay section (tank pump, etc) that clicks, second relay (ECU power stage etc) is connected OK. Inertia switch must be OK to power first section of double relay.
Battery warning light also flashes in sync.
MIL is never ON.

Tried
Three keys all behave the same.
All relevant fuses OK.
Disconnected battery for 30 minutes.
Battery new, volts good and cranks engine fast.
Earth connection voltage drop to block when cranking is low.
Cranking voltage good at about 11v.
Double Ignition Relay swapped, but it also checks out OK on bench.
With ECU unplugged, ignition switched voltage on ECU pin 69 is a full 12v, and ECU wake up on pin 66 about 0.3v less.
Crankshaft sensor between ECU pins 14 and 41 measures 340 ohms (a bit low?)
ECU main earth pins 33, 49, 51 and 53 continuity OK.
Cannot hear tank pump, but then it is being fed the interrupted supply.

Thoughts
At first I suspected the key antenna unit, but that should not cause relay clicking.
May be failure of CPH unit or ECU; the fact that the clicking starts immediately the key is turned might suggest it happens before the transponder chip is interrogated.
Could well be a broken wire, but how to diagnose.
It might be a protection feature operating, but what?
Unfortunately I do not have a Lexia.

Any help appreciated!

Fred

(I live in West Edinburgh)
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Re: Xantia HDI - ECU Problem

Post by CitroJim » 28 Jan 2016, 05:18

Fred, I'll have a think about this but in the meantime if any help can offer full wiring diagrams...
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Re: Xantia HDI - ECU Problem

Post by thorter » 28 Jan 2016, 09:54

Jim, that would be very useful and much appreciated. Fred.
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Re: Xantia HDI - ECU Problem

Post by CitroJim » 28 Jan 2016, 10:45

thorter wrote:Jim, that would be very useful and much appreciated. Fred.


I'll put the links up as soon as I'm back at base later this afternoon Fred...

Sorry I'm unable to do it immediately...
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Re: Xantia HDI - ECU Problem

Post by CitroJim » 28 Jan 2016, 10:55

Ignore the above, here's the Injection Diagrams Fred. It must be afternoon somewhere in the world...

Injection Circuit Diagram

Injection Harness Diagram

Injection Locations

I have the immobiliser/CPH diagrams too but will need to scan those...
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Re: Xantia HDI - ECU Problem

Post by thorter » 28 Jan 2016, 18:49

Jim, thanks for these. Particularly useful is the location diagram showing the wiring runs. The CPH diagrams would also be very useful. I have Revue Technique which only has the ECU circuit.
Vehicle is an estate, and despite ORGA 8654, the engine is L3 spec without the third electrovalve/inlet control. Possibly Heuiez were using up left overs?

One possibility I am wondering about is a short somewhere that would pull the ECU volts low, ECU disconnects, volts recover and the cycle repeats.

Fred
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Re: Xantia HDI - ECU Problem

Post by CitroJim » 29 Jan 2016, 05:06

I'll get the CPH diagrams scanned up as soon as I can Fred...

thorter wrote:One possibility I am wondering about is a short somewhere that would pull the ECU volts low, ECU disconnects, volts recover and the cycle repeats.


Yes, very possibly either a bad earth or supply feed, most likely high resistance somewhere that does not show on an ohmmeter continuity check or 'off-load' voltage check but will show when the ECU supply voltages are checked under load...

The loom running under the rad is a source of a lot of issues along with the engine bay fusebox...
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Re: Xantia HDI - ECU Problem - Fixed

Post by thorter » 31 Jan 2016, 22:39

Now fixed, and it did indeed prove to be a bad contact somewhere in the ECU main battery feed via the notorious engine fuse box. For the record, here is some of the gruesome detail.

It is a proper pain to get access for electrical measurements to the ECU/CPH/Double relay when it is all connected. From the ECU schematic diagram, I extracted a simple drawing of the very few connections that might cause the ECU not to start up. All this wiring checked out OK with a multimeter. Despite this. when put back together, EML light dead, key not recognised and fast clicking double relay.

I decided to open up the double relay to get access for checking, and this wasn’t too difficult. Warming the sealing compound, it became soft enough to scrape off then prise to break the cover seal without damaging the actual works. The relay supplying the primary power to the ECU was contacting, but the second relay for the tank pump and the separate preheat relay were clicking rapidly. Monitoring the voltages, the main ECU input on pins 1 and 29 seemed to be OK at 12 volts, but was fluctuating a little - cause or effect?

A difficulty is that a resistance measurement with a multimeter is at very low current, so the next step was to check the wiring at 5 amps load using a headlight bulb. The voltage dropped across the wiring should be a fraction of a volt. On connecting this to the double relay feed, at first the bulb did not light, but after a few seconds it did, reading a satisfactory quarter volt drop. But the initial delay was suspicious since the connection setup was solid.

So I added a bypass wire soldered to the double relay circuit board, and took this direct to the battery positive. Lo and behold, the EML lighted initially, the key was recognised, the engine started immediately, all warning lights out. Presumably when the ECU decided the connection was unsatisfactory, it disconnected and retried repeatedly.

I have yet to identify if the problem is the fuse box or the cross wiring, but the engine is running perfectly again. I would be happy to provide further detail if anyone needs it.

So Jim, thanks again, and I no longer need the CPH diagrams.

Fred
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Re: Xantia HDI - ECU Problem

Post by Hell Razor5543 » 31 Jan 2016, 23:09

Well done.
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Re: Xantia HDI - ECU Problem

Post by CitroJim » 01 Feb 2016, 05:18

Excellent news :D Well done Fred!
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Re: Xantia HDI - ECU Problem

Post by davoxx » 11 May 2017, 09:13

Sorry to dig up old thread, but this is what i think my xantias are suffering from.

Can you tell me which wire you passed the 12v to?
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Re: Xantia HDI - ECU Problem

Post by ekjdm14 » 11 May 2017, 12:05

Dave, sorry I don't know the exact wire as regards colour or number but I would imagine it's pretty easy to trace with a diagram. It'll be one of the thicker wires going to the relay. the one that will need permanent (fused) +12v is going to be the input side to the relay (obviously the relay handles switching of this supply to the relevant circuits).

A look at the relevant wiring diagram will no doubt show which wire is supposed to be the higher current supply into the pump side of the relay, all the thinner wires will be earth/switching current. Hope this makes some sense to you lol, just in case the OP doesn't come back with a number or colour to chase up.

Just in case nobody else comes back, could you remind me the years and engines of the cars you have with this fault? if my BoL covers them and I get a moment I'll look it up later if you need.
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Re: Xantia HDI - ECU Problem

Post by thorter » 11 May 2017, 17:14

Before you start cutting into wires at the ECU, here is the rest of the story.

After getting the car running with a wire direct to the double injection relay main feed (ie the ECU feed), I checked out the battery positive wiring. Voltage drop to the starter was good (very low) when cranking, so I removed the insulation going down from the battery terminal, which had gone hard and brittle.

In fact the main lead turns out to be a bundle of different leads, the starter, and three or four other less heavy wires, each going to a section of the fuse box. They are all crimped together in the battery terminal. About a couple of inches down was a mass of green corrosion, and quite a few broken strands. The separate leads are insulated further down, but not right up to the terminal.

I considered remaking the complete thing, but as the starter part was OK I removed the insulation from each wire until I had an inch length of good copper strands, fitted a split copper sleeve over them, and clamped the whole lot together with a couple of small hose clips. The sleeve was made from a short bit of 15mm plumbing pipe. Of course, clean the corrosion as much as possible, and insulate very fully.

Your may find something different, but this may be a possible place to start. Presumably the lead to the ECU was down to one or two strands, and the starting current of the fuel pump dropped the volts enough to cause the ECU to inhibit.

Fred
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Re: Xantia HDI - ECU Problem

Post by davoxx » 16 May 2017, 12:38

yeah this was an issue with one of the cars (99 2.0i turbo) - i had 2v at the shunt in the fuse box under the dash, giving it 12v made it work.


Thanks for your help.
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