www.jec.org.uk

I am finding that the FWD alert button constantly has the Red light on which then triggers a warning message on the panel of "Cruise control not available" followed by "Driver intervention" after 10 - 15 seconds the message goes away. It doesn't matter how often I press the button to OFF it comes on again after half a mile or so. I have adaptive cruise control and front parking sensors although I have never figured out yet how to activate them. Are all these items controlled by the one module and is it something that a Jaguar dealer should be able to identify easily on their diagnostic machine. Taking car over to Ireland soon so need it sorted asap.

Thanks in advance

Hi,
The adaptive cruise control and the front sensors (assuming we are talking about factory fitted items) are separate systems.

A Jaguar main dealer or a Jaguar specialist (with either the Jaguar equipment or the Autologic Jaguar diagnostic kit) should be able to diagnose the cruise control fault.

Jaguar front sensors are activated along with the rears either by engaging reverse or by pushing the overhead button marked 'P'. Hence, it sounds as if your car may have two distinct faults. Mike.

Mike.

They are both factory fitted items. Cannot get my head round the front sensors being activated by selecting reverse (must be a logic I'm missing ). I don't have an overhead switch marked P but that may be because it is a convertible, I do however have an unmarked rocker switch under the steering column which doesn't appear to do anything and the previous owners both state they never even knew the switch was there. Do you think a poor battery could cause this as I read on another forum about someone having cruise control error messages and that was resolved by replacing the battery. I don't really want to approach a main dealer unless essential as will cost "an arm and a leg" however I do want to get it resolved properly and asap so if their machine can instantly diagnose then will arrange it.

Cheers

Walter

Hi Walter,
The logic of selecting reverse to operate the front sensors is that you must be manoeuvring (eg parking) so the sensors front and rear will be useful. After such a manoeuvre, without a button to switch off the front sensors there is a risk of the bleeping becoming annoying in stop start traffic. Hence, Jaguar (unlike some other luxury car manufacturers) allows the driver the option of switching them off.

Have you checked to see if the front bumper sensors are present and that they are not simply blanking plates? Check for wires at the rear of each sensor position.

A failing battery can produce many spurious dashboard messages, typically accompanied by the need to frequently reset the window drop but unless your car has other symptoms it's unlikely to be the battery which is causing the cruise control failure. In all of this I assume you carry out regular checks on the car's lights and that the car's brake lights are working correctly because the simplest cause of failed cruise control is probably a failed brake light switch.

Any diagnostic session is only as good as the operator. Computer diagnostics are far from foolproof! Your local Region members would be the best people to ask for a local recommendation for a good specialist with the right equipment and a sensible labour rate. Mike.

Mike.

Brake lights are fine, no flickering fading. I wonder if the switch under the column is the isolator for front parking sensors. I have only had car since last august and it had a full service then so haven't looked at anything since apart from routine lights, coolants etc. Funnily enough it has developed a problem with window drop when roof being raised. The windows do drop but obviously not enough because seal ends up distorted when roof closes so windows need to then be dropped an inch and raised again. Window drop has been reset umpteen times but no difference made. The battery shows normal on gauge and starts first turn of the key, could it be voltage fine but ampage/current low. Have been to 2 local recommended Jaguar specialists who said mechanics/servicing is no problem but a dealership best for electrical diagnostics.

Walter

Hi Walter,

I also have a suspicion that your unlabelled rocker switch may have something to do with your front sensors since the Jaguar factory hadn't begun fitting front sensors to XK8s in 2003. If so, you will need the services of a competent (not necessarily Jaguar) auto electrician to sort it.

If you are lowering the hood and having window/seal problems, the finger does point to a less than adequate battery. However, the hood should only be operated whilst the engine is running to minimise the strain on the electrical system (see handbook caution) otherwise that may be a contributory factor to these issues.

One final thought about the ACC failure before leaving you arrange a diagnostics session - make sure the front number plate occupies the standard Jaguar position to avoid any risk of it (or any badge) obscuring the ACC beam and creating a failure mode. Equally, ensure the ACC front sensor is located securely and is not directing its beam in the wrong direction (incidentally, some failed units have been known to make excessive buzzing noises). Mike.

I spoke to the dealership that supplied car new and they advised front parking sensors were an extra supplied on the car at new. I think I will get battery checked (and replaced if neccessary first) as prev owner said car didn't get much use in 3 years he had it but car was permanently connected to a charger of some sort so that may have affected the battery anyway. Need to make sure I have radio code first

Walter

Car going into local classic car specialist (who used to deal with my MGC)on thursday who has a computer test machine which can fully check the battery for me. Apparently it can check everything, volts, amps, each cell individually so at least I will know about that side of it anyway.

Walter

Battery passed all tests fine and is OK Main dealer is next step to get it checked out

Walter

Good luck. Mike.

Cheers Mike.

Booked in for diagnostics on monday, fingers crossed they actually find a fault and its a cheap fix Took cover off column today and traced the 2 wires from it all the way to wiring into reversing park sensor so that partly answers that query.

Walter

Todays update, car had full diagnostic check and all fine except for the Adaptive cruise control module, 100 % defective . Price to replace is £2677 but if I get one secondhand they will fit and configure for 1/2 hrs labour, quite good for a main dealer I thought. Any ideas where I might pick a good working one up cheap

Walter

Eurojag! Details in our magazine.

Always good guys to deal with.

Mike K.

yep agreed, Euro jag and then our old mate Neville at NE Jagspares, 0191 586 7770, both a pleasure to deal with

The ACC units are ridiculously expensive from Jaguar. If you can't obtain a second hand one, there is an increasing number of repairers for ECUs, one of which might be prepared to tackle your unit. Try googling 'ECU repairs' to find one. Mike.