So with power on pin 1 of the stop light relay and the 3rd breake light working you have a good stop light relay closing and this confirms the brake switch and ground path through the ignition switch

This confirms you have the grounding trigger to the SLCM at pin BT2 - 1

So your signal on your meter should go to zero with pedal depressed at pin 1 when the SLCM connector is connected

The SLCM will be putting a voltage out on pin 1 as a feeler seeking a ground

This voltage should be B + or 12 volts DC but it can be less

 

Pin BT1 - 3 and the other side brake light pin BT1 - 9

We can assume the SLCU is powered as is hot at all times

This can be seen on page 93 and 95 as point 50 which is fuse # 1

 

Is relay #5 only for the high level brake light?

 

with the connector removed pin / socket BT1 3 through the connector / bulb / ground path will read the resistance of the bulb

So 18 ohms may be the resistance of the bulb if removed and tested alone

But there is a history of the ground being bad after the bulb in the lamp assembly

A limited ground quality at that point other then the bulb resistance would give you a indication on the instrument cluster and possible low illumination of the bulb

Have to ask if the correct bulb and if manufactured correctly ( cheap source )

 

Is relay #5 only for the high level brake light?

Yes and trailer light which is not being looked at at this time

So we are looking at the output at the SLCU at pin BT1 - 3 and 9 with the connectors installed so maybe the center pin on the bulb socket

You hade some values above

 

pin3 - right stop 0.0v
pin9 - left stop 4.4v

Does this change with pedal travel saying it is flipping or trying to do something , just not fully like a 12 volt output

So you have a poor SLCM output

 

Sorry, my mistake. I checked.piin #1 input to SLCM ( with SLCM disconnected) not pin #3.

 

Will need to find a volunteer peddle pusher and confirm.

Could you advise on how I can confirm this with the meter please. I believe this is done by measuring resistance probing pin1 and earth on the battery? If so then I am not getting zero at pin 1 with SLCM connected. I'm getting 12 Ohms and the value doesn't change on peddle press or release.

 

Let me wake up

 

I took a look at this thread and followed some of the steps mentioned here.

https://www.jaguarforums.com/forum/x...module-239469/

Specifically:

SLCM disconnected case open - Continuity from SLCM connector OY to SLCM relay chip leg 4 as marked; continuity yes
Disconnected from SLCM and light assembly; OY checked from SLCM connector to ground; continuity no
Disconnected from SLCM and light assembly; OY checked from light assembly connector to ground; continuity no
SLCM connected case open, car battery connected, ignition on position 2; 12V sensed at each of the three relay chips

I wasn't able to check that the bulb would light using an external battery. but I do have continuity.

Last test:



With the SLCM open and everything connected, check the voltages on the pin marked on the picture when the brake lights are "off" and when they are "on". When the brakes are "off", there should be no voltage on the pin or there could be some small voltage. When the brakes are "on", you should see a voltage of some 5V or 12V or some in-between. If there is no such voltage on the pin with the brake pedal pressed, then the problem is not in the chip but elsewhere in the SLCM. If, however, you see a voltage change to 5-12V on the pin (but the right stop light does not come on), then the problem is in that chip and it will need to be replaced.

I saw 4.5v on the pin with brake peddle pressed & 0.0v when released. So.... the chips faulty?

Correction. I saw 0.2v on the pin with the peddle pressed.

 

The brake switch and ground path through the ignition switch ( run position but not started ) can be tested as resistance on the meter with the SLCM connector removed at pin BT2 - 1 ( orange / green wire )

Don't use a mini volt meter but a larger one powered by a 9 volt battery . A mini is lacking omf or power to get a good resistance reading

The same can be seen at the stop lamp relay ( removed ) at socket 2 but with SLCM connector off

But since you do get the 3rd center light you can assume the ground path to the SLCM at pin BT2 -1 is the same and good enough

The reading may not be a perfect Zero but close enough

Your meter ground ( black lead ) can be at any good point on the car frame and there are a couple of ground stud post other then the battery negative terminal which is still a good point just longer reach maybe

WiFi keeps going in and out

We may be getting the BT2 - 1 position mixed up

 

Looking at your inside SLCM post but gotta run to the store first

 

Bulb socket side of the socket ground path close to zero resistance to car frame ?

 

The brake switch and ground path through the ignition switch ( run position but not started ) can be tested as resistance on the meter with the SLCM connector removed at pin BT2 - 1 ( orange / green wire )
My BT2-1 has is O (picture of connector above with numbered pins) - Checking resistance to battery neg terminal is 14 Ohms and doesn't change with brake peddle

Bulb socket side of the socket ground path close to zero resistance to car frame ?
11 Ohms with battery connected to negative strap
0 with battery disconnected and going straight to negative strap

 

Dealing with garbage Wi Fi

Going to store

 

Center pin voltage on bulb sockets with pedal depressed ?

A heavy garden stone works

Using connected battery negative cable as the ground point

 

0,36 right
0.08 left

high level brake light confirming brake peddle pressed.

 

Looking like the SLCM is not putting output and looking at that specific post

0,36 right
0.08 left

DC volts output on the bulb center socket pins ?

 

At the SLCM (9 & 3)?

 

at the bulb sockets center pin , everything connected , battery and SLCM