No crank/epb fault
 

Hi all.

Hope to figure out this problem on my 2005 3.0 v6 sport auto!
It started after overnight park up as usual and when i went to start following morning i received non crank/start situation with epb stuck on together with flashing epb warning and the usual parkbrake unable to apply plus g/box fault, dsc, abs fault.
This happened the week before but found a blown fuse f35 in boot fuse box which i replaced and all was good until now.
Put battery on charge so once ready will try again. Also getting p1797 fault code and unable to read engine ecu because of this fault together with solid pats light with ignition on? not sure if this is of any relevance although the non start is a bit confusing.

Any further ideas would be very much appreciated

Bad power - probably battery but doesn't have to be.

They don't always recharge or may do only to a very poor charge that won't start the car.

Put battery under load & measure its voltage accurately.

How does the starter behave? Is there any response when you turn the key, such as a big clunk from under the hood, or maybe a brief spasm from the starter but nothing more? Or are things totally dead, as if you had never turned the key? Big difference in how to troubleshoot, so please clarify. What about the lights on the dash? Do they respond normally, even if the starter itself doesn't?

The blown fuse? That's a big 'un, 30 amps. It feeds the parking brake actuator. Have you checked it again? However, even if that fuse were to blow again, that should not stop the engine from starting. It would stop you from releasing the parking brake, but it shouldn't affect the starter. I suspect the fuse blew because the battery voltage was low. There's a weird quirk with certain types of DC motors. When voltage drops, the amperage ramps way up because the motor is still trying to do its job. This can blow the fuse, when there's nothing wrong with the circuit other than low voltage.

Good on you for charging the battery. However, if the battery's overall health is marginal, it may not take or hold a full charge. I would suggest putting a voltmeter across the battery terminals. Have a helper turn the key to start. Under the load of the starter, it's normal for the battery voltage to drop, but not too much. 10.0 volts with the starter engaged is good practical minimum. Not sure if Jaguar published any specific minimum, but that is applicable to most vehicles.

No there is no clunk or noise except the relay activating. The dash lights stay the same and no dimming.
Have rechecked fuse 30amp and no issues this time. Have also inspected all fuses concerned with the epb. I would also say it blew first time due to loading but this time no idea unless the epb regulator is sticking maybe?
The p1797 code kinda throws me because it leads me to think it maybe broken connection somewhere although have inspected the connector at the epb and is clean and intact as far as visual checks go.

May sound silly but i think the inertia switch that i totally overlooked could also be my problem? I will check once battery is charged as i didnt here the fuel pump priming either when trying to start and may also account for an unreadable ecu? Fingers crossed

Ok so ive checked inertia switch and is working and while there also checked with a direct wire to double check the switch itself and no joy. The battery if holding correct charge so now havnt a clue? All fuses check out and have pulled ecu in case of water ingress but nothing. Yet again another power out causes the car to brick itself and probably due to more broken wires! Will more than likely bin this thing as soon as i find a replacement as being stranded is no fun.

@Andyg1971, what is the voltage across the battery terminals with the ignition in the OFF position when checked with a voltmeter?

12.8v and has been confirmed as fully charged and tested so really not the issue now

Has anyone checked the shift cable to the gearbox? There are two 10mm bolts that can work their way loose and cause a no-crank situation.

With the ignition ON, do the gear indicator lights on the shift console illuminate?

yes i have made a point of checking the shifter cables as well making sure the shift light is lit and moves in time with gear position. Also with ignition off the gear lever dose beep when nudged out of park so is operating as it should!
I also get the communication between the ignition key and gear lever.
Have run the epb direct from the battery and it engages and disengages correctly but dosnt operate from the lever in car although everything including the epb lever is lit up green as the other lights on the consul/gear lever bezel.
Have tested the brake pedal switch and is working correctly

short update as havnt had much chance to gain any ground with this problem.

Have spent much time reading and trying to understand the starter system but have also ruled out the starter motor and solenoid buy testing at the relay, therefore looking further back as more likely the switching wire to the relay or signal wire from ecu. Its a pain in the backside as yet again a wiring issue stops me using the car again.
Anyway progress is slow but positive

The EPB would not stop the car starting.

Unless there's some weird short or cross-connection, maybe (could that? I'm very doubtful) - but otherwise it's nothing to do with a start/no-start.

Exactly! hence looking at the starter system as epb and starter motor are operational when the system works as it is supposed to.
The system itself relies on a completed circuit of tests before it will signal a crank situation so maybe can or power/ground related no doubt but all will be confirmed once ive tested various parts of the puzzle lol

You mentioned the PATS light in your very first post?
What is that light doing now?
If flashing start counting the flashes as that's how it displays error codes.
.
.
.

Careful there. Prestart voltage is important, but is not the end all. The important measure is the voltage present under the load of the starter, when the battery is working its hardest. It's possible to charge a tired/marginal/failing battery such that it will show decent prestart voltage and give the misleading indication that all is good. But put a load on it, and it falls down. That's why I keep harping to measure the voltage at the battery while you turn the key to start.

Try a click test at the starter relay. It's R20 in the box under the hood. Put your finger on the relay while a helper turns the key to start. If the command to the relay is good, you should feel a good strong click. Other relays may click at the same time, so make sure the click is equally strong at R20. If no click, it's possible the electromagnet inside the coil has failed. Try swapping in a known good relay of the same size and try again.

If the click test still fails and swapping the relay was no help (no command signal to the relay), try putting the gearshift lever in N instead of P. See what happens then.

Have done all this and more hence the latest conclusion but will update as i find nonetheless .
Just takes time when your disabled but not impossible and am on the right track.

And what exactly have you found? I got some mind-reading pills on eBay, but they don't seem to be working. I even took off my tin foil hat, hoping to pick up a stronger signal, but no joy.

For example, what happened with the starter relay click test? Is the command going out to the relay, and is it responding properly? If no response, are you getting power and ground on the control (electromagnet) side? Both are switched, neither is fixed. Are you getting battery power to the other side of the relay, where the on/off contacts are?

What was the battery voltage with the key turned to start? You hinted it was okay, but what was the actual value? We don't really have an official limit from Jaguar, just more of a general minimum based on other vehicles. Too low points towards a supply (battery) problem. Too high points towards the control circuit not fully activating and putting a normal load on the battery.

We'd love to help you, offer suggestions, etc., but you've got to throw us a bone or two. ;)

Lol you clearly dont take the same pills as me then?
Battery testing found nothing wrong with power supply and this was followed through with testing front to rear power and ground cables and mega fuses.
The starter relay test was completed and tested all connections to it and from to be good and able to carry signal except when trying to crank this would lead me to the conclusion of power or can fault in not being able to complete and ignition cycle test upon cranking the engine.
Have done the both ecm to diagnostic port tests and found can- to be a fault to be showing high resistance at pin 123 ecu and pin 14 on diagnostic port.
Will now be working through can circuit from dsc module back, to rule out any issues with wiring.
As usual with this car no problem ever seems to be text book and i am no expert so although i would love to be able to spin off lots of jargon i probably wouldnt understand! i realise this will take me more time learning although i am not a total idiot and have been fixing and servicing my own cars all my life but sadly i am not an electrical engineer.
As i said i will update as i find