I am in the process of diagnosing a "NO HAZARD/NO TURN SIGNAL" issue on my 1992 XJ40.
Prior to this, the vehicle had no exterior lights whatsoever.
I replaced all the bulbs and still had no lights.
I removed and serviced the four bulb failure modules cleaned up the ground points and the following were restored.
1. Headlamps; Low and High Beams
2. Park Lamps.
3. Brake Lamps.
4. Reverse Lamps.
5. Rear Fog Lamps
6. License Plate Lamps.

When I turn the ignition 'on' the turn signal bulbs in the instrument cluster turn on during the system check mode. So the bulbs are good there.
As stated above, No Hazard or Turn signals.
Looking at the 1991 MY electrical schematic is getting me all confused.
It shows Logic ground as Black/Pink at the Bulb Failure Modules. However on my car they are all black.
I need a simple schematic (if there is one) to guide me through the process.
I can't seem to find the Logic ground for the central microprocessor DBC 10234 which is part of the Hazard/Turn Signal circuit.
I see the Black/Pink wires in the related harnesses but not where they all converge to a single ground point or multiple points.
Also, there is a Brown wire from DBC10234 that connects to the Door Lock Module but I have no constant 12 volts there.
I have temporarily tapped a separate 12 volt supply to get the door locks to work.
I even replaced the DBC10234 and still no power.

should have 12 volts here
Anyone with the proper schematic for the Hazard/Turn Signal circuits for a 1992 XJ40?

 

First of all I am no expert on electrics - I've reflowed a few modules/fuseboxes and done some simple tracing, but that's about it!

However -seems to me if you don't have power coming OUT of the microprocessor on the brown and you changed the unit (eliminating it as the fault) is it possible that you don't have power coming in?

Does the microprocessor ground itself through the case? When you reflowed the fuse box for the transmission fault, did you do the other fuse boxes too?

Larry

 

I inspected the passenger side fuse panel today and found nothing out of the ordinary. Every circuit leaving the fuse panels have power.
I have to verify which wire takes power to the microprocessor but the schematics I have are very vague.
Had to stop working as the heat down here is unbearable.
I will start again tomorrow morning.

 

All I could find was the 1990 electrical guide

HTH

http://jagrepair.com/images/Electric...Electrical.pdf

Larry

 

Just so as not to seem dumb, which of the modules under the passenger side dash controls the Hazard/Turn Signal.
Is it the ECM/Body processor DBC4968 or some other module.
I do not know if I am doing this correctly but I am just trying to trace the wiring.
All I can confirm for now is that I have constant 12 volts on the NB wire going into the hazard switch and 12 volts coming out on the path with the diode to the YP wire. The voltage on the YP wire cannot be confirmed with a test light. It will not light up. The voltage can only be read using a DVOM. I guess that is because of the diode.
The Hazard switch turns on when the ground is completed through the YR wire in one side of the switch and out the other side through the BK wire which is the Logic ground.
Touching two of the blue wires at the Hazard switch I can hear something like a relay clicking under the passenger side dash. I have to get a helper to see whats clicking there.
I am lost in the maze. The problem is the change of wire colors at the connectors.
All I can hope to do is ohm out the system wire by wire from the hazard and turn signal switches, since I don't know what the hell I am doing at this point.
This is the last major electrical issue I have to resolve on the car.

 

Still lost, but today I figured the following:
The 3 way connector (Black) is part of the circuit but I do not know how.
The 36 way Black connector LB13 is the Input to DBC4968 which is the Central Microprocessor. I have 12 volts on various pins on this connector. I have to see if there are numbers on the connector to trace each circuit.
The 36 way Yellow connector LB14 is the Output from DBC4968 the Central Microprocessor.

The brown wire with the black connector shown in the photo above is on the LB14 connector (yellow) output and goes to a Brown/Green wire to feed the Door Lock Module.
(This wire should have 12 volts to feed the Door Lock module. Presently, it is 0 volts).

The Hazard Switch circuit is on the green 24 way connector located in the left side footwell
The Turn signal switch is a 6 way plug above the steering column.
All Black/Pink wires in the harnesses have continuity to ground at present. Is that how it should be?
I was assuming that the microprocessor was what created the ground as needed to complete a particular circuit through the Black/Pink wires.
WANTED:
Does anyone have a PIN OUT diagram for the Central Microprocessor? If not, where can I find one?

 

I guess no one has any answers for me regarding the hazard/Turn Signal issue.

I visited a "British" auto repair shop today.
I was told $130.00 per hour with a minimum of 1 day to find the problem. In addition to that the cost for parts and labor to install said parts.
The owner told me the charge would be around $1500.00.
For under $100 I can rewire my car with a conventional Hazard/Turn Signal system using part of the OEM circuitry.

 

Hi sanchez,

Sorry for the late reply - busy days. The pinout info for the CPU is given in the Electrical Guide on the various relevant schematics, such as Turn Signals, Central Locking, etc. You can download the manual here if you don't already have it:

Jaguar XJ40 Electrical Guide 1991-1992

Cheers,

Don

 

Don, I have that.
What I was looking for is the connector pin out for the LB59, LB60 and LB61.
If you look at Fig 5 and 5A of the 1993 Electrical Schematic you will see what I am looking for.
LB60 is input to the CPU
LB61 is output from the CPU.
The 1993 Schematic will not work for me as the power supply to the CPU is LB59 which is a 6 way connector which in the 1992 does not go to the CPU.
What I am trying to find is the constant and switched 12 to the CPU.

 

Ah! You want the pinout for the connector, not the CPU. You didn't say that!

I can't recall whether Jaguar ever published that information for the cars prior to '93, but you should be able to count pins on the connector starting at one corner as pin 1, trying different corners as your starting point until you find the correct wire colors connected to harness pins that are the correct number of pins from pin 1. The connector may even be marked at pin 1.

Alternately, you can count the pins in the connector on the CPU and then find the mates of the pins you need in the harness connector.

In these types of connectors, pin 1 is usually a pin closest to one corner of the pin array, and the pins are numbered sequentially starting at pin 1 and continuing to each successive row of pins. I've sometimes seen exceptions where the rows of pins were not continuous and the numbering was not completely sequential, but you can usually do enough deduction to find the pins you need when you factor in the colors of the wires.

 

I have resolved my "No Hazard/Turn Signal issue today.
After checking the circuit that sends power to the CPU, I had 12 volts at the back of the fuse panels but only 4 volts at the Brown/Green wire that feeds the CPU.
The harness from the Left fuse panel is tucked high up under the dash.
I started by removing the instrument cluster and upon removal, I saw the problem so I did not have to dismantle the dash any further.
The PO had someone install an Alarm system in the car, which I promptly disabled when I got the car.
Whoever did the alarm install, tapped into the 12 volt wire feeding the CPU and in the process had damaged some other wires as well.
I guess that with the heat the 1 inch piece of tape they used to insulate the wires became unstuck and the CPU feed was shorting to power hence the voltage drop.
I also learnt that a Short to power will not cause a fuse to blow rather, it will send the power through a different route.
I removed all of the alarm wiring and I properly repaired the 3 damaged wires and 12 volts was restored to the CPU.
All CPU functions have been restored.

Now I wait to see what Hurricane Dorian will do to my area.
I will continue my XJ40 saga after the Hurricane passes.
I have now completed all of the electrical faults that the car had.

 

sanchez,

Kudos on your achievement! It has taken some real persistence, but you've done it! Your search for knowledge and information and your enthusiastic approach to resolving every issue have been truly impressive!

Thank you for sharing your journey with the rest of us. Your contributions to the forum will be of tremendous value to other members for years to come.

Looking forward to the next installment in your renovation, and prayers that the hurricane has little or no impact on Florida or any other area in its path.

Cheers,

Don

 

Maybe I spoke a little too early.
I decided to use the car this morning to pick up some sand bags for the hurricane and I observed the following:
Turn signals, Flashing as they should with the left or right side light flashing inside the car.
Hazard lights flash on the outside front and back but no flashing lights on the dash.
I may have to pull the cluster again to see whether I missed something.
I do have a spare circuit board and switches for the Hazard, Front and Rear fog lamps.
I will work on that after the storm passes through.