I hope you´ll suceed..........

 

One last question:

releases the fuel filler flap with key in ignition switch too?

 

Gah... replacement ECM + matching KTM + matching transponder key = crank but no start. Same as before including not-very-helpful "ENGINE FAULT" messages. So it's not the ECM. Even tried the new ECM with the old transponder key and the old KTM but it would even fail to crank with those, as expected (security).

I put all my old kit back in after that; all of the BPM items work fine (seats, filler flap, lights) but it really is the only unit I haven't looked into yet, but I can't just put a replacement in, the car will probably just say "incorrect part fitted" without some WDS work. So I will have to get the car checked by an expert next week. Frustrating stuff.

I double-checked the fuses, relays and inertia switch before putting the battery back on charge.

 

Sorry for you,

but, even without all other issues, an ECM with LNC.... would never work in a 1997 car which need a LJA1410.. ECM!!!!!!
That´s the problem with the early XK8´s.
Why do you refuse to check the BPM?
A last other try is to check the starter relay (i know it cranks), respectively its connection to the ECM.

 

Yes, LNC1410BB ECM is 98 on.
From what I understand, it can't be substituted for a 97 but, all else equal, I'd expect it to at least start.

Back to basics: you need compression, fuel and spark for the engine to run. Which can you confirm?

 

Frank,

Have you tried: Old ECU, NEW KTM, NEW key? Try this if you can, and capture the codes! Without capturing the codes, you are flying blind. Let the computers help you.

Best of luck, keep us posted.

 

Won´t be a know-it-all,
for me the problem is the B1595 fault in the BPM.

 

The LNC ECM was for a 4.0 AJ26 with two-pin coils, just like my car, so I figured it might be enough to test with.

Starter relay is fine, and it just concerns cranking for which there is no issue.

The car has compression but has no spark and no fuel. Both coils (via ignition odules) and fuel are getting 12V but not the negative which comes from the ECM.

I tried combinations of KTM and keys, but it refuses to even crank whenever the wrong key/KTM combination is present.

I have not been ignoring the BPM, just leaving it until last as it's one item I can't just replace without reprogramming (which requires my car to be towed). Having pulled the BPM, its cabling was secure and in good condition; the circuit board is fine, no burst capacitors or any visual sign of failure. I may see if BBA-REMAN can take it and test it

I pull the codes but they are still the same as always. No P-codes, but lots of BPM codes. Dunno how that affects starting though, thought that was the ECM.

 

Hi,
Apologies if these seem like random musings, and feel free to contradict/correct.
I’ve searched for the start-up sequence for the XK, and found this on Gus’ website in one of the training manuals:
http://www.jagrepair.com/images/Trai...2002-20-02.pdf

“
Engine cranking and starting are controlled by the ignition switch, ECM, BPM, P / N signal, key transponder module, ignition key reader exciter in the ignition switch, ignition key transponder and the gear selector not-in-park switch.
Cranking and starting are accomplished in the following manner:
Ignition key switched from the OFF position
• KTM receives a signal from the ignition switch position I as the key is turned
• KTM energizes the reader / exciter, which causes the key transponder to broadcast its security code
• If the key transponder code matches the programmed KTM code, the KTM outputs an OK TO START signal to the ECM via a serial data link
• ECM receives OK TO START signal and transmission P / N signal (hard wired from transmission), and enables fuelling and ignition
• ECM outputs a SECURITY ACKNOWLEDGE signal to the BPM via a serial data link
• BPM receives a park signal from the gear selector not-in-park switch and enables cranking if the security system has been disarmed
Ignition switch to position III (CRANK)
• Ignition position III crank signal is received by the BPM
• BPM grounds starter relay coil to energized starter motor
• ECM receives starter relay coil signal and sets engine starting values
“

So it would appear that the security system is exonerated, as suggested, since you have crank.
You state that you have fuel pressure: - does this mean that the fuel pump runs for a second or two after switching ignition to position ii, or is that only after bridging the relay?

If you are getting fuel pressure at the rail, then do I understand correctly that both the ignition coil and fuel injector relays are energised and supplying power to the coils and injectors?

I’d agree that the 98 ECM, although not valid as a permanent replacement, would at least allow the motor to start: - from Vehicle - Specification Changes and Enhancements Information, 1998

“ECM
Software changes are introduced to support the revisions to the exhaust camshafts (10° earlier close). On NAS vehicles, additional software changes are introduced to operate the leak check of the fuel tank and evaporative loss system. As a result, the 1998 ECM cannot be installed in a 1997 MY XK8.”

Issue does seem to have similarities to the thread posted by toaster, although the OP didn’t report an ‘engine fault’ message – perhaps as it was an XJ rather than XK.

As if the ECM can't see/ignores the motor rotating?

 

Maybe deleting the DTC`s is the simple solution.................................

ADVANCED JAGUAR ELECTRICAL SYSTEMS
Service Training
2.2.6
Student Guide
Date of Issue: 02/15/2002
JAGUAR ELECTRICAL SYSTEMS: CONTROL MODULES
Control Module Configuration (continued)
How Programming Affects Diagnosis
When diagnosing electrical malfunctions, assume that no defect exists in the relatively robust CM hardware in the
vehicle. Since a defect is more likely in connectors or switches initial diagnosis should concentrate on these compo-
nents. Inputs and outputs can be monitored via the diagnostic equipment, if these are proven to have no fault the
failure must lie with the control unit.
There are two malfunctions of a control unit:
• A hardware problem
• A software problem (Programming).
Approximately 80% of all control units that are replaced have a software problem that can be either corrected by
performing a hard reset (disconnection of the battery power supply) or reprogramming of the hardware. It is sug-
gested before any modules are replaced a hard reset and/or reprogramming should be carried out. Several options
are available with WDS: Program New Module, Program Existing Module, Dealer options, Setup and configuration.
On vehicles that cannot be programmed via the diagnostic equipment, note the 3 conditions below before inter-
changing control modules between identical vehicles to confirm diagnosis.
1. Refer to the illustration on page 2.2.5, which shows a typical VCATS label, located on the floor of the lug-
gage compartment of XK8 models. Each label is specific to each individual vehicle, and lists the VIN of the
vehicle along with the part numbers of the CMs originally fitted to the vehicle during manufacture.
2. In the example on page 2.2.5, the part number of the Body Processor Module is identified as: LJA2500AG/
1055. In the illustration, the basic part number LJA2500AG has been programmed during vehicle manu-
facture for the specific market and features of the vehicle concerned, and is identified as 1055. This would
be the complete part number for a replacement BPM for the vehicle concerned if it were necessary to
order one from Jaguar Parts Operations. Note that the suffix 1055 (in the example above) does not appear
on the label on the CM concerned. This number appears only on the VCATS label of the vehicle.
3. It is permissible to
temporarily
interchange a CM from another vehicle for testing purposes, only if:
a. The full vehicle history of both vehicles is available
b. The history of both vehicles indicates that the CM in question has not previously been replaced by a
CM from another vehicle or by a replacement part
c. The VCATS label information for the full part number of the CM in question on
both donor and
recipient
vehicle is
identical
, as illustrated above.
d. The donor vehicle is known to have no electrical defect.
Always disconnect the battery
first
, and reconnect it after connecting the replacement CM. The possibility exists,
particularly for control modules that control the movement of door windows or power operated convertible tops,
for inadvertent uncontrolled operation of these systems if the battery remains connected during such operations.

 

Agree with Toaster's post, re: looking for problems outside of the modules...here's a simple one that hasn't been mentioned: have you checked to see if the big ground strap that bolts to the transmission under the car is securely attached?

Also, in the high power something, something module in the trunk (with the 250 amp fuses), one side runs the starter motor. The other side runs other engine related functions. Have you tested continuity on those fuses? (that wasn't a very educated explanation, but it's been awhile since I tested - and found - failed fuses back there.) Worth a shot.

 

If you like gambling:

BODY PROCESSOR MODULE (BPM) LJA2500AG - Jaguar XK8 Coupe 1996-1997 | eBay