I am having an intermittent no-crank issue with my 2001 XJR. I have studied the forum for info and poured over the wiring diagrams for the XJR.


I am documenting my progress hopefully for the benefit of all. This may take a while, but I don't give up easily.


Also, the info that I gleaned from the forum, shown further down, says to check the Shifter Quadrant at the cable. Can someone tell me what the Shifter Quadrant actually is?


I formatted this as best I could going from Word to the Forum. Apologies.


And as always, all the input, experience and wisdom of the forum members is always appreciated.




NO START NOTES 02/21/15

• Drive car to restaurant for breakfast. Driver door inside handle broke
  • Had to be let out using outside handle
  • This has nothing to do with the no-crank. It just made the day more special.
• After returning to the car, it would not crank (Was the ‘P’ illuminated? I don’t remember, but I think so)
  • Gear selector lock would not disengage when pressing brake and ignition in position II
  • Messages Engine Fail and ASC Not Avail displayed briefly after the no-crank
• Manually tripped gear selector lock and exercised gear shift. This did not resolve issue
• Tried starting in neutral…….. no go
• Waited a while and tried to start……… no go
• Exercised the brake switch by lightly depressing the brake pedal until I could hear the switch click. Exercised the brake switch a bunch of times. Then tried to start……… it did. The gear selector interlock also resumed working.

• Study XJR wiring diagrams
  1. Learned that the Dual Linear Switch notifies the Body Processor Module that the car is in Park or Neutral. The XJR does not have a rotary switch located on the transmission.
  2. The BPM controls the crank/no-crank based on the input from the Dual Linear Switch and other inputs.
  3. The Brake Switch provides input to the BPM to make the decision to trip the gear selector lockout solenoid. The wiring diagrams do not indicate that the brake switch is a necessary input to successfully crank the engine. Also, I have started the car many times in Park without the brake pedal depressed, so that seems to line up with the wiring diagram info.
  4. Researching the Forum and learned:
     1. P1797 is a Control Area Network (CAN) error
     2. It can be caused by a faulty module residing on the CAN
     3. It can be caused by a CAN wiring issue
     4. It can be the result of a Dual Linear Switch failure

The Dual Linear Switch can cause a no-crank issue that would be followed by a P1797.

ACTION ITEMS:
I am taking the following actions that if not successful, will lead me to replacing the Dual Linear Switch. I don’t have the ability to read/interrogate the modules on the CAN. I can only read OBDII codes.
My progress is being controlled somewhat by the very cold temperatures we are having, ice and snow.

1.  
   1. Check voltage at the battery. (02/22- measured 12volts)
   2. Clean ABS connectors. The ABS is on the CAN and I recently repaired the motor solder connection on the logic module circuit board)
      1. Motor Connector (02/22 - cleaned)
      2. ABS module connector (02/22 - cleaned)
      3. Clean connector adjacent to ABS pump (12 pin connector (02/22 - cleaned)
   3. Swap out Starter Relay (This would not cause the gear selector lockout. The BPM controls the gear selector lockout and the Dual Linear Switch provides a signal to the BPM confirming that the transmission is in Park or Neutral), but a flaky Starter Relay could cause a no-crank. The BPM triggers the Starter Relay. If this is the cause, the gear selector lockout not tripping could/might be a BPM logic error caused by the P1797. I am thinking outside the box here. (02/24 - replaced)
   4. Exercise the Dual Linear Switch briskly to possibly clean the internal contacts.
      1. Inspect to see if the switch is loose on its mounts (02/24 – exercised)
   5. Resume driving the car with fingers crossed.
   6. If problem persists:
   7. Clean Instrument Pack Connectors (weather permitting)
   8. Chase down and clean ALL CAN connectors
   9. Remove the center console, and replace the Dual Linear Switch ( Possibly open and clean. Adjust install position)
   10. Check for slack in gear selector cable

NOTES TAKEN from FORUM

P1797is a code for the CAN communication from the engine controller to the transmission.

Are there any other codes or is that the only one?

If that is the only one and it only happens at start up and never while you're driving, I'd guess a dirty connection, the relay that powers the transmission control module or even a weak battery. These cars are finicky about voltage and old batteries can cause all kinds of strange behavior.


There are three devices with mechanical adjustments that are involved in the start interlock system:

-- brake switch
-- shifter quadrant at cable (02/24 – I don’t know what the shifter quadrant is)
-- dual linear switch at shifter

They should all be checked for proper adjustment before replacement is considered.

When the car will crank but not start, check the following with the key at position 2:

-- does the interlock relay click when the brake pedal is touched?

-- is either P or N illuminated as relevant to the position of the shifter?

Failure of either of the above indicates the component out of adjustment.

Starting after jiggling the shifter or moving to N is a sure sign of problems with the interlock.

This condition can also be induced by a weak battery. A battery can pass a load test and still be weak because the charging system cannot keep up. Certainly load testing and returning to service without charging leaves the battery in a less than optimal state. Try a full 24 hour charge using a good charger and see if the problem goes away for a while.

Given the code and the recurring symptoms, I like the idea of going after cleaning all of the CAN bus connectors.

Once upon a time Old Mike (wonder whatever happened to him, been years) had the same problem. Chased it around a while, then replaced the brake light switch which was failing intermittently. Apparently a PIA task unless you are fairly small, light with small hands.

Did it once on a my Range Rover, but there was more room to work. Now, Old, weak, large and arthritic, I would take it to the dealer or my local Indy.

Yep! Replaced mine a few days ago and was a royal pain working in a small area.

It resolved ALL my issues and this will resolve this posters problems as well. So, order a brake light switch. I got a used one from Ebay. Good luck!

It resolved ALL my issues and this will resolve this posters problems as well. So, order a brake light switch. I got a used one from Ebay. Good luck![/QUOTE.

Well, since my brake switch is most likely the original, I will go ahead and replace it and continue checking all the CAN bus connectors. The brake switch isn't on the bus but its output is watched by the ECM, so who knows what goes on in the mind of the ECM.

I apologize for the long post, but there is much information that I discovered from the wiring diagrams concerning a no-crank. My problem is not resolved as yet, but I have Brake Switch on order and my fingers crossed.


All input is appreciated.




BRAKE SWITCH ANALYSIS


The Brake Switch provides two inputs to the ECM on two different connectors per the wiring diagram and is used to cancel Cruise Control.

• The first connection to the ECM is EM82-08. This is a direct input from the Brake Switch
• The second connection to the ECM is EM80-20. This is also a direct input from the Brake Cancel Switch. Since the labeled ‘Brake Switch’ and ‘Brake Cancel Switch’ are both connected to connector CC40, pins 1,2,3 and 4, It appears that the Brake Switch and the Brake Cancel Switch are in the same physical unit.
  1. The Brake Cancel Switch’s purpose is to cancel the Cruise Control without turning off the cruise (so you can resume). It connects from Pin 3 on the Cruise Control Switches and Pin 2 on the ECM.
  2. The Brake Switch output goes to the ECM (Engine Control, EM82-08). Pin 1 to the ECM and Pin 4 to power.
• The Body Processor Module, BPM, controls the Gearshift Interlock Solenoid and the Starter Relay. It receives input indirectly from the Brake Switch and Directly from the Not-In-Park Microswitch located at the Park position of the Gear Shift.
  1. The input from the Brake Switch to the BPM path is:
     1. Brake Switch to ECM
     2. ECM to the Controller Area Network (CAN)
     3. CAN to the Gear Selector Illumination Module back to the CAN
     4. CAN to the Instrument Pack then to the Standard Corporate Protocol Network (SCP)
  2. Input from the Not-In-Park Microswitch is direct to the BPM on Pin 58.
     
     So, now seeing that the BPM is ultimately responsible for activating the Starter Relay and the Gearshift Interlock Solenoid, it is reasonable to replace the Brake Switch.
     
     It is also important to note that the BPM will activate the Starter Relay without the Brake Switch being closed (foot on brake pedal) as long as the Gear Shift is in Park or neutral (Not-in- Park Microswitch). If the car is in neutral, the BPM would learn this from the Dual Linear Switch at the Gear Shift.
     
     Complicated huh?
     
     To recap, to crank and start the engine the following must work together

• Brake Switch
• Not-In-Park Microswitch
• Dual Linear Switch
• CAN

I plan to do the following as next steps:

• Check the CAN and SCP connectors on the Instrument Pack. Clean and check for corrosion, and pins that have been pushed out of alignment. I have already checked and cleaned the ABS, ECM, TCM, Illumination Module and Dual Linear Switch connectors.
• Check the Not-In-Park Microswitch for consistent function when tripped. Just because a microswitch clicks when tripped, doesn’t mean that it is opening or closing. The same is true of the Brake Switch.
• Replace the Brake Switch.
• Then is all of the above fails, clean or replace the Dual Linear Switch.

Good detective work on your part. Thumbs up.

Brake switches are a common item on those cars. In fact many brake switch failures occur with all manufacturers. I would go with new only. There have been many updates over the years to those switches.

One thing that came to mind was the CAN. I remember many of these cars doing a no start intermittent but mostly (not always) when the engine bay was very hot. Like happens a lot in florida, kind of thing. We eventually found the problem to be a diode in the left front engine bay fuse box that was inline of the CAN network. I don't exactly remember the repair but I think it involved replacing the fuse box. I remember always seeing a low brake fluid message on the instrument pack display whenever this occurred. It was a sign that the CAN went down.

As far as the shift quadrant. All I remember about those shifters is that the linear switch was on the side of it. I think there is a cable adjustment (I believe others would be referring to as the quadrant) and the linear switch adjustment. The cable adjustment is two large nuts that control fore/aft movement of the cable and is mounted on the right side/rear corner of the shifter.


Hope this helps a little.

Your input is a great help. It tells me more about the quadrant and alerts me to the existance of a diode on the CAN. I will check to see if I can find the diode in the wiring diagrams. Also, something has to terminate the ends of the Can.
Do you know if the CAN is terminated by the modules (ABS and Instrument Pack) or a separate component (resistor / diode / etc.)?

I saved this a while back and have not studied it yet, but it may be of use.

CAN Physical Layer and Termination Guide - National Instruments

I think motorcarman posted information on the termination and resistance of the CAN network. One end is the ABS module and the other is probably the INSTPAK. Maybe someone will remember and help.

The network diagram in JTIS may be hinting where the terminators are. It's drawn as if they're in ABS & inst pack.

Bob said https://www.jaguarforums.com/forum/x...ght=terminator

Hey BlackX300VDP,


In your experience with Jaguar, was there ever an explanation as to why the Brake Switch that does not have direct control/input over whether the engine will crank or not, can cause a no-crank situation?


Thanks.

You did not ask me, but if it is true, I suspect it might have to do with the requirement in some markets for the brake to be depressed before the engine cranks. In fact, new Jaguars in the US have that "feature".

Even though it is not necessary to depress the brake pedal to crank and start the engine on the 2001 XJR, something is causing either the ECM or BPM to decide to not crank.

I would love to see the programming source code for those modules to learn what might be happening.

So would a lot of us!

I personally have not seen a brake switch cause a no start on the X308 cars. Yes, the later cars need the brake pedal depressed but not your car.

What is your PATS light doing? Is it flashing during the no start? Is it on or off? That light will tell you if it is a security concern or not. The cars will crank and not start if there is a security concern.

I ignorantly got rid of all my old Jaguar paperwork from classes and the like when I moved houses. I know I had information in there for your concern that would help so now I'm going on memory.

If the PATS light is the red light, center top of the gear shift module, it was not lit or flashing during the no start. Weather and body willing, I will be replacing the brake switch this weekend. Based on the wiring diagrams, I don't see how it could cause this, but am willing to give it a try. I will post results, but it could take a while to find out since the issue seems random. Anything else you can remember will help us all. Thanks.

It's usually top of the dash by the front windshield. Engine off, flashes every 2 (?) secs.

I replaced the Brake Switch. The car started, but it started before I replaced the switch as well. I let the car run a bit, stopped it and started it again a couple of times. All was good. So while I was at it I replaced the driver door handle cable so I could open the door from the inside. Success! Easy job.


Then, I decided to take the XJR out for a drive. It would not crank. I tried jiggling the gear shift, exercising the brake switch, starting in neutral, etc. No crank. The Park Light on the gear shift module was lit and the PATS was not. I know that the Park Micro Switch is OK because the car beeps at me whenever the gear shift is moved away from the Park nesting position.


Just for fun, I measured the voltage at the battery. It was 11.83 volts. I put a battery charger on the battery which brought the voltage to 13.49v. The car cranked. Joy! But the joy was to not be for long.


I disconnected the negative lead from the battery and put the charger on it for a couple of hours. I then disconnected the charger, measured the voltage at the battery and got 12.57v. I get 12.49 v at the positive cable ends to the fuse and relay boxes and to the ECM enclosure in the engine compartment.


I then tried to start the car. No crank. Then the messages TRAC NOT AVAIL, ASC NOT AVAIL, ENGINE FAIL and INCORRECT PART INSTALLED. Also, the Climate Control displayed the message 'Err' and beeped several times.


I have not been able to get the car to crank again, so I have put the battery back on the charger and will do a hard reset.


Any ideas? The problem is not the Brake Switch.

It sounds like the battery may have an internal problem and will not hold a charge. Once it's charged again measure the voltage while some one tries to start the engine. I expect the voltage to drop off below 10 V.
All those codes are a symptom of a weak battery.