Hi.
So i had to do some welding to my x300.
very close to ecu ,front corner, jacking point floor area. Battery not connected. I was very carefull with all moist rags and all but still something went wrong.
Now Battery connected interior lights work and seats move....al fine, but try to start , power on, get no lights to dash. No warning/checklights or anything. Only dim backround light what goes out if i try to crank. I hear small click , not solenoid but a relay i think. Totally killed my lovely dailydriver. Hope someone can guide what module is the first to swap? Hapily many available ..ebay checked.
Br. Heikki

 

The ECU is electrically not powered until 2 relays closed , so not hot at all times

That doesn't say if there was a way for power getting into ECU from a back circuit

In starting the BPM ( hot at all times ) sums up the enables so the BPM provides a ground path to close the starter solenoid relay on top

You would have to feel the relay click by hand and this cuts the starter rotation issue in half

There is a hard reset of both the BPM and SLCM ( a starter enable to the BPM ) and the ECU ( which is not resetable ) is another BPM starter enable

Ask Questions and feel that relay as more then 1 clicks at the same time

Pics coming

 

Wifi iffy tonight

Try jumpering with a paper clip between the 2 white wires of the inertia / crash switch . low current

 

The starter solenoid relay has 2 fuses # 3 / 25 amp left engine bay fuse box and # 12 / 10 amp right engine bay fuse box

 

This starter solenoid relay can be swapped with another of same part # like a headlight , fog , or A/C clutch

The other 2 relays that must click closed to power the ECU ( for the starter enable ) is the small # 9 right engine bay fuse box , and fuse 10 . 12 , 14 , 16 in that fuse box

And the large right # 5 ECU controlled relay , there are also 2 fuses for that relay , but the starter should rotate without this relay closing , but no fuel injectors

 

Battery positive post fwd ?

 

There is a quick test to see if power is " controlled " to getting to all points of car

Have key in run position but engine not started

Remove the relay in the corner of each fuse box and it should click in your fingers back to open

The 5th relay as the left engine bay fuse box only operates the 2 car horns so is a swapping option

In each of the 5 fuse boxes fuse 1 - 9 are hot at all times

Fuse 10 , 12 , 14 , and 16 require the relay in the corner of the fuse box to close

the remaining fuses are hot at all times

 

Bed time in the USA

 

Thanks Parker.
After pressing reset button near ecu i got dash lighted.
No crank tough. Nothing clicks when trying to start. Relay swapped fuses checked. Odd is that airbag light goes red when trying to crank. Still working. Big thanks, lots info to read, and understand😀.
edit. Noticed that chk engine light goes off before trying to crank.... immobil. In ECU?

 

Dumb recommendation, but I thought I’d add anyways:

What is the condition on the battery? These cars are finicky with having a solid battery. Slightly undercharged at startup can cause weird things, specifically like this, to happen.

 

Good question so i checked. Seems to be almost 6 y. Old if one faded label numbers were date, so time to change. Its been a strong starter for now . Every now and then it does not crank from the first key turn tough but second try ok. Like it does not reg. the key.

 

Your going to need a new battery so good to work from a good battery base

The inertia switch can be finicky and not manually reset so the jumper between the 2 white wires

Your pressing switch may have made momentary contact to reset some lights sequence but on releasing it is back to bad

Your manual reset may have gotten you something better

If you pull apart the inertia switch spring loaded parts will fly everywhere

New battery as 6 years ( before testing to see ) is way over due

" Nothing clicks when trying to start "

That includes putting finger on the starter solenoid relay ?

The airbag does go through a normal self - test for a period on car start and should go away so nuisance in this case

Your immobilization ( chip in key ) on your non - North American Specification model ( NAS ) ...............

There is a devise ( labled reader / exciter control module ) by the ignition key barrel as the transponder to the chip in key with an exciter antenna coil ( on the key barrel ) between the 2

B!MCP has a picture

How to test the immobilizer alone ( ? ) a good result is the all good starter enables which commands the BPM to provide that ground path to make the starter solenoid relay click

In the end Andy ( XJREngineer from the original X300 design team ) in England can blank the immobilization parts inside the engine ECU as worst case

To see the immobilizer device ( labled reader / exciter control module ) external to engine ECU as it is wired is on page 207 ( middle of picture ) section 15.4 Security as the SLCM gives both engine ECU and the BPM it's start enable ( digital between the SLCM and both ECU and BPM )

jagxj1996.pdf

Best you can do is see if it is powered on pin # 1 other than build a device to tickle the antenna / coil but then you would have to dig it out to meter pin

Or instrument lights interpretation

You can command the starter solenoid relay to close by providing a ground on the pulling relay control coil or jumper with heavy wire and blade wire ends the sockets 3 and 5 , high current

To give you some joy

 

The airbag light works as it should in selftest and goes out as does chk engine before crank. When i try to crank
airbagl. Goes red when cranking.
tried extra power from other battery with cables but no help. Maybe inertia swich got some heat . Welds were VERY close . So ill try to find working one.
If i connect those 2 white wires in inertia swich it should crank?

tomorrow i get my son to feel those relays.

Sorry, takes time to understand everything as English isn't my native language. More questions to come.
Big thanks .

 

English is not native to English as well

So we can do a lot of head scratching for a bad battery

" If i connect those 2 white wires in inertia swich it should crank? "

This does allow engine cranking as it worked for me as I ended up jumpering the 2 white wires as the previous owner had a crash on front right side


To find a working inertia switch is iffy as the donor switch may have tripped from a crash and commonly not able to reset which is a case from reading others

The purpose of the inertia switch is to kill the engine which it does by stopping / opening the fuel pump relay and other those on the fuse boxes " king " relays ( one does include the right engine bay fuse box relay which powers the engine ECU off the top of head ) that may not include starter rotating engine ( engine ECU starter enable comes into play here though ) so there is a wiring pic on page 40 , but then takes time to wrap you head around and how it is all related

Your paper clip between the 2 white wires at the inertia switch does keep a ground path through the ignition mechanical switch to keep the relays closed as points 5 , 6 , 7 , 8 , and 9 double hash stopsign

5 - right heelboard fuse box relay ( this is your #1 fuel pump relay pulling coil control power as fuse # 10 ) not to be confused as is 6 double hash circle ( not below in next written text line )

6 - left heelboard fuse box relay

7 - right engine bay fuse box relay ( this is your engine ECU power as fuse 10 , 12 , 14 , and 16 )

8 - BPM power ( starter solenoid relay closing ground path providing / command )

9 - not found

 

New battery, no go.
next stop, inertia swich.....

 

The main feed cables from the battery to the front fuse boxes and starter/alternator run inside the inner sill behind the carpet on RH Side. There is also a main loom that runs there adjacent to the battery cables. Could be those have been heat damaged as your welding would have been very close to them.

 

Brendan ,

Deep

You went too far in disassembling your example to show him your work

At least you left it a daily driver with the steering wheel in place ......................albeit on the wrong side

 

Hi all.
Yes everything is possible as sparks might find the way to wiring no matter how well i protected those. I did some welding near seat also. Carpet off and lots of moist rags everywhere. . I just cant find any damage .
ill inform what will happen when ecu..inertia and others arrive. Some testing today also....

 

Ok so the broblem was Ecu. In Estonia there is a company with lots of x300s in pieces so i got 1994 4.0l ECU from there. Now running again. My org ECU has a sticker saying "Reworked to lna 1410 wd " and late 1997 date so whats the difference? If someone knows,please tell. Inresting to hear.
Thanks all for help.
br. Heikki

 

Probably has to do with this TSB , PROM chips update for updated EGR valve , you may not even have a EGR ( top of intake manifold ) as some X300s don't like I think England ( country / region emissions dependent ) or supercharged

05.1-26 amend4 (R493)

If your running good with what you have with the installed changed engine ECU......................

Idle speed good ? Do not adjust the throttle position sensor