Hey, i recently bought a 2004 s type in (mostly) pristine condition. I'm very happy with the car but I does have a few issues. #1 on the issue list right now is a sound that appears when i accelerate pasta 60mph(100 kmph). There are no warning lights illuminated at this point.

I can cruise at 55 mph all day without any issue but if i accelerate past 60 with either the cruise controller or the gas pedal, an electronic "thrumming"/high frequency beeping sound immediately pops up. This happens without fail every time I accelerate past 60. The sound does not go away with time. It appears to disappear on downhill stretches even if the speed is still above 60.

I have not been able to pinpoint the exact location of the sound but it appears to be emanating from somewhere behind the dash or in the foot wells.

I did have the car checked out by two independent workshops, the first did a basic check and found nothing while the second did find some fault codes:
B1318 low battery voltage
U0100 lost communication with ECM/PCM "a"
U0155 can communication fault with instrument cluster
U0415 invalid data received from abs unit
P0706 drive mode sensor range/performance
The battery voltage appeared to be slightly on the low side at 12.45 v despite plenty of driving around so i topped up the charge and now the voltage is 12.9 volts. I tried measuring the voltage drop during cranking but it does not appear to drop below 11.5.

Anyways this does not take away the problem. I'm guessing it has something to do with the pcm and possibly the throttle body. Since the sound is triggered by both the cruise control button and the gas pedal i guess both are fine.

Anyone have any ideas?

 

PCM is about your last suspect.

Tyres maybe.

If you have the sound then use the J-gate to change gear but keep the same speed does the sound change much / a lot / or what?

 

Thanks for the reply. Interesting point. If it is the tyres wouldn't the sound be constant above 60 mph?

As it is, the sound disappears the moment i release the gas pedal, irrespective of speed. It definitely has an "electronic" feel to it.

I will try to shift gears and see what that does.

Sometimes it does seem that the gas pedal needs to be floored to get the car moving though this night be subjective.

I can also say that the car was sold to me with existing "wheel vibrations" so i got the wheels checked out and rebalanced right away. That seemed to take away the vibrations. It didn't help that the seller had grossly overinflated the tires. reducing the pressure made the ride a lot smoother.

2004 jag s type.

 

Also could be a wheel bearing.

 

I'm almost certain that the sound is generated electronically. The slightest pressure on the throttle at 60ish mph brings it on. It does appear to be engine load dependent since the car will accelerate quite happily to the new set speed(beeping all the way) and once it reaches this speed it will stop beeping. I will try to record the sound tommorrow.

In any case, I had the bearings checked out by two independent workshops. No issues found. I tried shifting with the J gate and it made no difference. Any acceleration past 60ish results in the beeping. It seems to be coming from the right hand side of the car.

I've tried drowning it out with music but it doesnt do much to mask the annoying beeping.

2004 S type 2.5 V6

 

Could the noise be some sort of interference reaching a stereo speaker? Any change if you switch off the stereo?

 

Sounds reasonable. I can't imagine that the ECM itself can beep so it could be one of the speakers or perhaps I'm hearing the throttle body opening? This could explain why the noise goes away when a steady cruising speed has been reached(throttle body opening stays the same)

Turning off the speakers seems to make no difference though. Perhaps they are powered up regardless of whether the head unit is on or not.

2.5 2004 Stype

 

It's most odd. Doubt it's the TB, but ... (what else? dunno)

 

At this stage this seems to be the most likely cause. I will try to get the mechanic to drive and listen closely to the speakers.

Now that i think about it it seems highly unlikely that the sound might be from the throttle body. In that case it would be drowned out by the engine noise.

 

Consider getting one of these, a Steelman Engine Ear #65001 electronic stethoscope:

https://www.steelmantools.com/engineear-stethoscope


I have one and it is AMAZING. It is great for tracking down the source of noises. The microphone is highly directional and will pinpoint noises. I once used mine to find a leaking AC evaporator. It let me find a tiny pinhole leak by the nearly imperceptible sound of leaking refrigerant.

Have a helper drive while you carefully poke around. I bet this will find it.

 

Thanks for the tip! Thats going in the shopping basket along with an odb reader.

 

Do make sure that the OBD unit is Jaguar specific. Generic code readers are of limited use on our cars....

 

I went ahead and bought an icarsoft cr max https://www.icarsoft.com/Product/s-3...ft_cr_max.html

It appears to have support for most of the Jaguar models as well as what appears to be a very comprehensive list of ecu's. it appears to be the same list of functions/ecus that their Jaguar specific service supports.

 

I'll be very interested in what you find. AFAIK, there are only three components in the cabin designed to make noise:

1) The stereo speakers (multiple locations)
2) Tone generator for chimes, turn signals, etc. (instrument cluster)
3) The backup alarm (rear parcel shelf)

Did I miss anything?

That's not to say there isn't some other component somehow making noise, but that seems very unlikely.

 

Seems reasonable. It's unlikely that this is an intentional feature or a sign that an electronic component is on the verge of failure.

I have been at home with sick kids the past few days so I've not been able to go to the mechanic but i did get the obd reader. There were a lot of codes which i think were caused when the battery voltage dropped too low.. i reset them all and it seems like the car now has a bit more low down torque. Drove about fifty KMS and no new codes yet.

I'll try to get the stethoscope tomorrow and try to pinpoint the sound with a friend.

S type 2.5

 

I suppose the other possibility is a non-Jag add-on.

May be tough to find

Could be anything, even a speed limiter.

 

update: I managed to get someone to drive while i poked around with the stethoscope. The sound seems to be coming from all the speakers in the back.

Now i need to filter the interference. I'll pull the speaker fuse first and see if that sorts things out.

 

Maybe. Look in the trunk and see if you have the booster amp mounted on the underside of the shelf. If you do, at idle, wiggle the connector plugs on each side gentley. if one of those plugs has wear, it might start humming through the speakers. It can get louder at speed or you just are noticing it. Good luck.