My beloved 1994 Facelift XJS (UK model VIN ...19594, AJ16 engine with Auto box) has gone from spluttering to now not starting after little use over a snowy winter. Mechanic has tried everything else for the weak spark and suggests a new engine ECU.

A replacement engine ECU (pic attached model LHE1410BE/701 date of manufacture 28/06/94) seems impossible to find!

Does anyone know if a Lucas 15CU part DAC11505 from an 02/94 XJS or an X300 ECU (which look similar) part LNA1410GF/316 would work?

Any other suggestions? Have changed coils, O2 sensor, crankshaft sensor, cleaned ECU contacts.

 

Does the AJ16 have digital ignition (I assume it does)?

If yes, then you've probably got some ignition amplifier module. These can cause problems. And it does as it looks...

SNG Barratt - The Ultimate Jaguar Parts Specialist

For ~£35, I'd replace that first...

 

I think (but not sure) that the ECUs in AJ16 cars are also part of the security system so you have to do something clever to fool them into thinking that they are in the right car.

Have you checked injectors for good spray pattern plus change fuel filter and check fuel pump operation ? All can cause this sort of problem. Also check the connection on the engine position sensor. It's only role is to signal position to enable starting. Try swapping the Engine Position Sensor for a known good one.

Good luck

Paul

 

alec,

AJ16s don't use that ignition amplifier. That's only used with the old coil ignition system on AJ6 engines.

Paul

 

X300 have immobilizer, XJS have not. It will be problem.

 

If XJ300 have immobiliser and XJS do not then maybe an X300 ECU can go into XJS but not the other way round?
The car has the standard Jaguar security system with remote key fob and alarm but no transponder chip in the key. Not sure if it has an immobiliser.
What about whether the older Lucas 15CU ECU would work?
Anyone out there got an LHE1410 ECU to sell or able to diagnose and repair them?

 

Alec,

We have club members who have transplanted supercharged AJ16 engines and their ecus from x300s into XJSs and they have this problem of getting the ecu to interface to the car. You have to fool the x300 ecu into thinking it's still in an x300.

A dry joint on your ecu is a possibility, but more likely is moisture getting to the ecu connection plug. Have a look at that. Failed ecus are not a common cause of an XJS not starting or running properly. I've never heard of a failed ecu on an XJS amongst our club members.

I think there are a lot of other possible causes before I'd even start thinking about changing an ecu. Go through and check all the components in the fuel and ignition systems logically before you condemn the ecu.

Hope that helps

Paul

 

I had water in my AJ16 ECU 2x. Probably 3x since my grandfather thinks they changed it when the car was still his and only a few months old back in 95.

My xjs is garaged and not my daily driver. But gets washed a **lot**.....there are others who have had the same problem. Water finds its way down thru the bulkhead from either external water or a/c drops.

Solution is to seal the path with silicone and to use ECU connector synthetic grease (it's a FORD part number, and it's not dielectric grease found in your parts store) all over the pins above the connectors themselves.


And you must find a AJ16 XJS ECU. I don't know that the last two digits are so important, since I have gotten 3 used one from wrecked AJ16 XJS as a back up with different letters (LHE 1410XX) and they all worked fine in my car when I tested them. The ECU from the X300 will not work
Good luck !

 

Thanks Mark.
I have had problems with water leaking (probably from windscreen/cowling junction) into passenger footwell although the ECU connectors look fine.
Would you or anyone (in the UK easier) be interested in trying my ECU in their AJ16 XJS to see if it works or lending / selling me a working one? These LHE1410 ones are really difficult to source! I can't find anyone in the UK who tests or refurbishes them for a reasonable price? I don't think AJ6 engineering do sadly.

 

Have you checked the throttle butterfly? They get gummed up and don't open properly.

 

alec,

I'm still not sure why you think your mechanic automatically thinks you've got an ecu problem. You mention having a "weak" spark. That implies coils, plugs or wiring rather than ecu. Is it really a "weak" spark or is it a mistimed spark which implies engine position sensor?

Has he gone through the ignition systematically identifying where is the problem rather than expecting you to just throw money at the problem. Does he have a good knowledge of AJ16 XJSs?

Good luck

Paul

 

Although common, I don't think your coils are going to prevent the car from starting. That sounds like a crank sensor.

Sadly, with the AJ16 XJS's it IS sometimes necessary to throw a few parts at the car because it's an archaic OBD2 System and won't accurately tell you which of the electric ancillaries has failed. If you know that there has been water dripping on the ECU I would venture to say that this is the problem. When my last ECU went out before the water-proofing, I though that it had survived the water....until the car started having the same problems again, and on the advice of another member , I took out the ECU and put light pressure on the pins with a spectacle screwdriver, and surely enough the pins damaged by water where loose like teeth in a mouth with gingivitis, and one pin even snapped right of. But they did not look corroded at all.

 

Thanks all.
It's not an AJ16 XJS specialist but they've takien advice from a couple. It did idle a little and lose a strong spark but now it doesn't crank with a weak spark. We've changed all six coils and checked the wiring. Haven't yet changed crankshaft sensor or engine position sensor. Will try those first.
The ECU pins look clean apart from a dash of white copper salt on one. Will massage them with a screwdriver to check - haven't opened the ECU's inner compartment yet Took the covers off and couldn't see anything obviously corroded or burnt but the real clockwork is inside that I think.

 

Stupid question perhaps, but are crankshaft sensor and engine position sensor same thing or is engine position sensor an additional part?

 

Alec,

Not a naive question at all. Many people don't understand the difference between these various sensors, particularly as they often get given the same acronym - CPS.

The Crankshaft Position Sensor is mounted on the front of the engine and creates a signal based on seeing the gaps in a toothed ring mounted on the end of the crank. It constantly sends a signal to the ecu to adjust ignition timing based on the timing it sees between each tooth. Failure of the CKPS is a common cause of starting problems.

The AJ16 doesn't have a Camshaft Position Sensor but it does have something similar which is an Engine Position Sensor. It is mounted on the right front of the engine where the distributor used to be on AJ6 engines. It indicates the TDC position of the engine (on the compression stroke of the cylinder) in order to enable the ignition firing sequence on starting. Once the engine has started, it doesn't do anything. Again, if that had failed it would prevent proper starting.

On AJ16s, CKPS seems to fail more often than EPS. You mentioned in your first post that you'd changed the CKPS.

In theory, neither of these, or the ecu, will give you a "weak" spark. They all determine the timing of the spark but not the power of it. If you have a "weak" rather than a mistimed spark, I would still look at coils, plugs and wiring first. What has made the mechanic say that you have a "weak" spark?

It should be possible to monitor the CKPS and EPS signals, but maybe not so easy for an amateur.

If the engine is turning over quickly but not firing, I would:

- Remove each spark plug in turn and check that all spark plugs are sparking properly (which should verify coil and plug)
- Put fresh fuel in the tank (eliminates possibility of stale fuel, especially if you haven't used the car over the winter)
- Check the fuel pressure on the rail (verifies fuel pump and filter)
- Check wiring connections on EPS, CKPS and ecu plug

If all the above is ok, then I might replace the CKPS for a known good one. After that I would change the EPS for a known good one.

Only after all of that would I even start thinking about ecu failure.

Hope that helps

Paul

 

Has the Throttle potentiometer sensor been considered. That freaking part seems to cause all sorts of mystery problems. The inability to get it properly diagnosed coupled with the cost of the part makes it a hard part to throw at the car without knowing if it will work in advance.

 

Engine position sensor changed and still no joy.
So am still seeking a new ECU! Part LHE1410. If anyone able to source / sell a working one please let me know!
Cheers.

 

I've now sourced an ECU part LHE1410AG/601. It's had 2002 and 2003 PROM upgrades and been rebranded LHE1410AL.
How does this differ from my original ECU LHE1410BE/701 ? What's the difference between the 601 and 701? Does it matter that I have a UK RHD car and it's from an LHD US car?

 

IDK if anyone has really documented the software variances or hardware variances (if there are any) between ECUs. There ARE sensor differences on the emissions side between some cars, and USA cars don't have an immobilizer to interface with unlike UK cars. If you put a USA ECU in a UK car, I have no idea if it would just ignore an immobilizer or not. We know that there has been on and off success swapping ECUs between X300's and XJS AJ16 cars, others have had problems.

Often ECUs are updated in a series, and newer ECU iterations are workable on older cars.

E.g. from Jaguar Classic Parts for AJ16 cars (not 3.2L versions):

AJ16 ECUS

XJS
S (Spain?)
4.0 Automatic
TO VIN 221299
LHE1410AG601
LHE1410AH601
LHE1410AJ601
LHE1410AK601
LHE1410AL601
FROM VIN 221300, FROM VIN 221300 - TO VIN 222631, TO VIN 222631
LHE1410AH601
LHE1410AJ601
LHE1410AK601
LHE1410AL601
4.0 Manual
FROM VIN 221300 - TO VIN 222631
LHE1410AH602

J & P (Japan & Portugal?)
4.0 Manual
TO VIN 221299
LHE1410BG702
LHE1410BH702
LHE1410EC702
LHE1410ED702
FROM VIN 221300 - TO VIN 222631
LHE1410BH702
LHE1410EC702
LHE1410ED702
FROM VIN 222632
LHE1410EC702
LHE1410ED702
4.0 Automatic
FROM VIN 221300, FROM VIN 221300 - TO VIN 222631, TO VIN 222631
LHE1410BH701
LHE1410EC701
LHE1410ED701
FROM VIN 222632
LHE1410EC701
LHE1410ED701

A (Americas?) 4.0 Auto from 221300
LHE1410BH703
LHE1410EC703
LHE1410ED703

C (Canada?) 4.0 Auto
FROM VIN 221300, FROM VIN 221300 - TO VIN 222631, TO VIN 222631
LHE1410BH704
LHE1410EC704
LHE1410ED704
From Vin 222632
LHE1410ED704

N (N. America?) from Vin 221300
LHE1410EC705
LHE1410ED705

Brazil, N
LHE1410ED705

X300
4.0 Litre,automatic
TO VIN 754303
LNA1410AH
LNA1410MB
↳LNA1410MB00D
↳LNA1410AH00D
↳LNA1410AJ00D
↳LNA1410AK00D
↳LNA1410AL00D

4.0 Litre,automatic, emission A, LWB
TO VIN 787953
LNA1410DC
FROM VIN 787954
LNA1410DD


4.0 Litre,automatic, emission A
FROM VIN 754304, FROM VIN 754304 - TO VIN 787953, TO VIN 787953
LNA1410VG
LNA1410VH
FROM VIN 787954, FROM VIN 787954 - TO VIN 802986, TO VIN 802986
LNB1410AC

4.0 Litre
FROM VIN 787953
LNA1410WC
LNA1410WC00D

4.0 Litre,automatic, emission C
FROM VIN 787954
LNB1410CB

4.0 Litre,automatic, emission D
FROM VIN 787954
LNB1410CB

4.0 Litre,automatic, emission E
FROM VIN 787954
LNB1410CB

4.0 Litre, emission C, LWB
FROM VIN 787954, FROM VIN 787954 - TO VIN 802986, TO VIN 802986
LNB1410FC
FROM VIN 802987
LNB1410FD
LNB1410FD00D
LNB1410FE00D

4.0 Litre,emission A,USA,Mexico,S,Canada,V,Taiwan
LNA1410AJ
LNA1410AJ00D
LNA1410AK00D
LNA1410AL00D

4.0 Litre,automatic,emission A,LWB,USA
LNA1410DE
4.0 Litre,emission A,USA,Mexico,S,Canada,V,Taiwan,less LWB
LNA1410VJ
4.0 Litre,automatic, ,unprogrammed unit,less USA,less Mexico,less Canada,less Taiwan
TO VIN 787953
LNA1410WD
4.0 Litre,automatic,emission A,USA, ,Mexico,Canada,Taiwan,unprogrammed unit,less LWB
FROM VIN 802987
LNB1410AD

XJR
4.0 Litre supercharged,automatic,emission A
TO VIN 754303
LNA1410JA
FROM VIN 754304, FROM VIN 754304 - TO VIN 782980, TO VIN 782980
LNA1410SC
FROM VIN 782891, FROM VIN 782891 - TO VIN 787953, TO VIN 787953
LNA1410SD
FROM VIN 787954, FROM VIN 787954 - TO VIN 802986, TO VIN 802986
LNB1410DB
FROM VIN 802987
LNB1410DC

4.0 Litre supercharged, emission C
LNA1410TC
FROM VIN 787954, FROM VIN 787954 - TO VIN 802986, TO VIN 802986
LNB1410EB
FROM VIN 802987
LNB1410EC

4.0 Litre supercharged, emission E
TO VIN 754303
LNA1410TC
FROM VIN 787954, FROM VIN 787954 - TO VIN 802986, TO VIN 802986
LNB1410EB
FROM VIN 802987
LNB1410EC

~Paul K.