Yeah- A no load battery voltage test is one step better than worthless. The voltage should be above 12 volts with headlights on and well above 10 volts while cranking.

 

This morning I was preparing to put the XJR battery on a long charge to see if that would correct the problem. Before I disconnected the battery, I put the key in the ignition, and turned it to Position II, and pressed the brake pedal. The gear shift interlock operated. It did not operate yesterday during the no-crank drama. So, I tried to start the car. It fired right up, the climate control beeped at me four times and then all was normal. I had a check engine light, but did not have any error messages from the instrument pack.


I did not read the OBDII codes this morning because it most likely is the P1797 and yesterday, during the drama the OBDII code reader could not establish contact with the ECM to pull the codes. I know. I should have tried to read the codes this morning, but it is too late now.


Go figure.


So today's plan is to:

• Charge the battery. Maybe the extended cold weather, minimal use of the XJR and testing wore the battery down. Or, maybe it just needs to be replaced.
• Test to see if the car cranks and test the voltage at the battery when trying to start.
• Pull, clean and inspect the instrument pack connectors while the battery is disconnected.
• If it cranks and starts...............drive it, but only turn it off when in my driveway.

This is getting to be very frustrating, so my mind jumps around a bit and thinks that other possible causes could be:

• Dragging starter.............. slowly killing the battery
• Bad Starter Solenoid
• Flaky Body Processor Module. I have a spare BPM with the same part number and revision. Can it be installed without programming?

As always, I appreciate your input and your support.

 

Have you cleaned up the grounds and positive connections ? It sounds basic, but a dodgy ground can cause mysterious issues. I had an intermittant no start that was due to nothing more than the battery ground strap - connection at the crimp.

 

I have cleaned some of the grounds in the engine compartment and the positive connections to the engine fuse boxes and Ecm enclosure. There are more to do.
Where is the crimp you refer to?

 

The crimp is where the braided ground cable attaches to the ends. I replaced my cable with an old-school round cable. Some people have soldered at the crimp.

 

UPDATE, March 3, 2015:
I charged the battery. It was reading 11.83v. It then read 12.86v.
After sitting overnight, the battery read 12.24v (no load). I tried starting the car and it started right up. I shut it down, disconnected the battery and proceeded to clean all the grounds and the 12v+ supply cable termination points.
I cleaned all the ground points except those under the dash ('A' Pillar) and in the console area. Those I will do very soon. All ground points looked clean. They are much cleaner now and shiny. The only ground that I found to have minimal to marginal corrosion was the ground for the EMS Relay and fuse box on the driver’s side of the engine (U.S.). It is shiny now.
I pulled the Instrument Pack Veneer and facing so I could access the connectors. They looked clean but I used electrical spray cleaner on the plugs and the instrument pack PC board pins anyway. They are definitely clean now.
I buttoned the car back up and tried a start. It fired right up and did so a few more times like it should. I drove it around town for awhile. It was great to drive it again.
Is it fixed? I would not bet on it at this point. Time will tell.
Later that day, I had a thought. The only other mechanical switch that I know of to play a part in the ‘crank’/’no-crank’ decision is the Fuel Shutoff switch.


The Fuel Cutoff/Inertia Switch normally provides a path to ground from a pin on the BPM through the Ignition Switch when in Position II. Additional ground paths are also provided to the BPM, but for different purposes. When the switch is tripped, the ground mentioned above is removed and a ground is provided to the ECM62 connector, pin 12 of the ECM. The ECM would not allow a crank and would not allow the fuel pumps to run with this ground present.


So, if the Inertia Switch is not tripped, but dirty/corroded causing an intermittent ground signal to the BPM, maybe, just maybe, it could cause the BPM to not allow the engine to crank. I have not seen the source code for the BPM or the ECM, but the code probably only handles expected inputs like ground present on a certain pin or not. I doubt the software was prepared to handle intermittent grounds or voltage signals.

I located the Fuel Cutoff switch and pressed the rubber enclosed button. It clicked! I did not expect a click, but since I had never touched the XJR type switch before, I was not sure what to expect. I don’t know if it was a full click or partial click.

The Fuel Cutoff switch on my ’95 XJS does not click unless it has been tripped. In my experience with my ’95 XJS, the Fuel Cutoff switch has been tripped by just being bumped while working on the passenger side of the vehicle. Maybe, just maybe, the XJR’s Fuel Cutoff switch is just as sensitive and had somehow been kicked or jarred enough to cause this. I also checked for water ingress and damage to the switch, but saw none.



So, my next step now, is to drive the XJR around town and always try to be in my driveway before cutting off the engine. I will also, be cleaning the console and ‘A’ pillar grounds soon and may also tap on the Fuel Cutoff Switch with a rubber mallet to trip it and then reset it multiple times to clean any dirt/corrosion that may be on the internal contacts.


We will see.

As always, your input is appreciated.

 

Let us know when / if you get this resolved. Mysteries are often inciteful (sp?). TIA.

 

Sounds dead battery, beyond charging.

 

Yeah, it sure has the old battery sound to it! Charging fixes a discharged battery, not one with a bad cell or diminished capacity from age.

 

UPDATE, March 15, 2015:

I have completed the following: (Sorry about the formatting. The forum engine is having a field day with my WORD doc)

• Replaced the brake switch as suggested by the Forum. I do not believe that this was the cause of the problem. The problem persisted after replacing this assembly with a new unit.
  
  The wiring diagrams do not support the brake switch being the cause, although many forum members swear by it and through the mystery of the ECM’s ‘smoke-and-mirrors’ could play into many symptoms that forum members have experienced.
  
  The brake switch assemble contains two micro switches. One is normally open and closes when the brake pedal is pressed to activate the brake lights. The other switch is normally closed and opens when the brake pedal is pressed to disengage the cruise.
• Checked and cleaned all ground points

•  
  1. Noticed that the 12v cable attached to the starter was not tight. It was not finger loose, but required minimal effort to back off the nut.
  2. Cleaned the positive 12v cable to the starter and to the solenoid
• Finished inspecting and cleaning, using electrical contact spray cleaner, all connectors that make up the CAN bus.

• Inspected and cleaned connectors that connects the SCP Network to:
  
  1. The BPM
  2. Inspected and cleaned the connector to the Dual Linear Switch
• Tested the CAN as described in the CAN Network Troubleshooting guide (Jaguar Service Training) found in the forum stickies. I will repeat a portion here.

1. Rechecked the Inertia Switch (Fuel Cutoff Switch). It no longer clicks when pressed. It clicked the first time that I checked it. It is a player in whether the car will start or not. It may also be a player in the crank/no-crank decision made by the ECM and BPM since it provides a ground (one of many) to the BPM when in normal state and when tripped, removes the ground from the BPM and adds a ground signal again, one of many) to the ECM.
2. Had the battery load tested. It passed, although I am not 100% confident that Advance Auto interpreted the results correctly. They said that it showed 12v during the load test. I am just not so sure about that. The battery, I think, is two years old (it has a 12/12 sticker on it).

The most significant factors found so far are:

• Dirty ground feeding the engine ECM fuse/relay box
• Loose/Not-Tight positive cable connection to the starter
• Inertia Switch not fully seated as it should be
• Extremely cold weather that could/would exaggerate any weakness in the battery

I have resumed driving the car around town, but am careful at this point to not stop the car until I am back in my driveway. I did however stop the car at the Post Office this past weekend and the car started right up when I left.

I am not fully convinced that the problem is resolved, and am uneasy, but time will tell.

 

Just a note on the CAN bus. 60 ohms across the CAN pins with all modules connected. 60 give or take a few ohms due to meter tolerances. The voltage on the CAN is to roughly equal 5 volts between the two. I usually saw 2.3 on one and 2.7 on the other. That is what I went by but the main idea is the two equaling 5.

 

Based on the info that the sum of the CAN high and low side voltages equalling 5volts, it looks like my CAN bus is OK. That is a relief and allows me to concentrate on other factors that may be the cause. Hopefully, the root cause has already been touched. I will continue to use the XJR and see if the no-crank issue surfaces again.

 

The CAN bus is a communication signal bus, so voltage levels only give an overview of potential problems. Any partial ground or loose connection can still trash it. You would need a scope to really tell what is happening. That said, I think you are wise to look elsewhere.

 

Thanks for the feedback. If the problem continues, it may be time to clean or replace the shifter linear switch.
I will keep the forum posted.

 

If I insert the key and turn it fast before the car finishes all its self test, it will not crank.
If I insert the key and wait a second it starts every time. This might be unique to my car, but it has been that way for a few years.

 

Same here!

 

Yes, the slight delay is the PATS system. It is slower than we like. Some cars are more noticeable than others. The ring around the ignition barrel reads the key then it goes across the network to the BPM then goes across another network to the ECM to give the okay to crank. After all the challenge questions go back and forth across the networks and are correct, it'll crank.

 

The timing of the start/crank attempt and the finish of the System Check may well be part of my problem.


My problem first manifested itself when I was running the engine in the driveway so I could observe the AC clutch cycle. While watching the clutch, the engine just shut off. No sputtering, no drama, it just shut off like someone had turned the key. I tried to restart, but experienced the no-crank symptom for 3 start attempts. The car then cranked and threw the P1797 code.


Now that I have cleaned all the CAN connectors, grounds and positive cable ends, cleaned the BPM connector, cleaned the starter and starter solenoid connections, reset the Fuel Cutoff Switch, charged the battery and now have weather temps in the 50s and 60s, the car, so far, cranks every time.


I have also changed my starting routine to wait for the System Check to complete before cranking.


I will continue to wait for the System Check to complete which is a small price to pay, but know that is/was not the entire problem.


I am glad to have completed cleaning all the connectors and grounds. At 14 years old, the car can only benefit from that activity.


I am still very suspicious of the Fuel Cutoff switch. It did click when I pressed the reset button. In subsequent checks after driving the car, the button has not clicked. Maybe the switch was not fully tripped and was interrupting the needed ground signal to the ECM intermittently causing a no-crank decision by the ECM/BPM. Speculation on my part. I am tempted to buy another Fuel Cutoff switch just so I can disassemble it to see how it is constructed.


For now, I continue to drive the XJR, but my trust level has not been restored and I am hesitant to turn off the engine except when in my driveway. Time will tell.


I will keep the forum updated. Thanks to all.

 

Wish we could up the RAM in it.

 

I drove the XJR around town today running errands. When starting, I always waited until the System Check completed before trying to crank the engine. All went well until my last attempt to leave my driveway.


I was waiting for the System Check to complete and then received the messages:

• ASC Not Available
• Trac Not Available
• Engine Failure
• Wrong Part Fitted, and
• The Climate Control beeped at me 6 times, I think it was 6, and displayed 'Err'.

The shifter interlock would not operate when the brake was depressed and the car would not crank. I could hear a relay click when trying to crank and noticed a brief dimming of the instrument pack lighting. Moving the shifter to the left from its Park position caused warning beeps as normal. I did not think to check to see if the 'P' light was lit during this occurrence. It has been lit during previous occurrences.


I tried to read any codes stored, but was not able to establish communication with the ECM, so no codes. I measured the battery voltage, no load, at 12.14volts. I know. A no load measurement isn't worth much, but I did not have anyone around to help.


I did a quick Hard Reset procedure which specifies that you remove the negative battery cable and place it on the positive cable while still attached to the battery for 30 seconds. The same error messages were given at System Check and the shifter interlock remained locked.


I then placed the negative battery cable on the positive cable, still attached to the battery, and left it for an hour.


I then reattached the negative battery cable to the battery and let the car do its System Check. The System Check completed, the Climate Control beeped 4 times, the shifter interlock resumed working and the car cranked and started and the CEL was now lit.


I was then able to read OBDII codes. They were in order:

1. P1797
2. P1000
3. P1797

So, this proves that what I have done so far, has not resolved the problem.


I guess that my next move in this process will be to replace the battery and resume driving to see if the problem occurs again. If it does reoccur, then I suppose it will be time to replace the dual linear switch.


Any suggestions and shared experiences are welcome.