System fault display

Q My 2006 Jaguar Sovereign 2.7 TDVI has been giving me this problem for some time now. When starting the car, the system ‘dings’ and it sounds as if the starter/engine kicks back on the second compression voltage drop. The fault code ‘handbrake fault’ shows on the speedo display, which locks on the handbrake. Up until now I have disconnected both battery terminals, held them together for 10-15 seconds, reconnected the battery, started the car, applied both the footbrake and handbrake together and off you go until next time.

I have cleaned the earth terminals beside both headlamps, plus the earths next to the brake servo, and fitted a new battery. I have also removed the starter motor, cleaned the mountings and had the terminals cleaned and tightened, as well as fitting a battery conditioner. Now I can start the car about four or five times and the fault appears whether I charge the battery or not!

I bought a digital voltmeter which runs from the cigar lighter and I now think that the alternator is ‘lazy’ – ie, when the battery is fully charged, the voltmeter shows 14.4 volts and the voltage drops after each start until the handbrake locks on at around 12 volts. Even when the engine is cold, the alternator will show 14.4 volts initially and gradually drop as the alternator appears to soak up heat. Oddly enough, the car will start OK after clearing the fault, even if the meter shows 12 volts for the next four to five starts. There are no fault codes logged. Michael Polglase

A The most likely problem is that there is a fault in the electric parking brake module software. This was a known problem and can be rectified by reprogramming the electric parking brake module. As you also have discrepancies on the voltage readings, I would inspect the earth connections to the parking brake module and also check for any resistance in the earth leads between the battery, body and engine.

Although you have cleaned all the connections and replaced the battery, I still believe that the problem is related to current flow. It may be worth trying to connect a second earth lead between the engine and the vehicle body to ensure there is a good flow of current when required.

Another possible cause is that the parking brake motor is failing and drawing too much current. Jaguar did release a technical bulletin about the electronic parking brake, but this was applicable only to vehicles up to 2005.

There is a reset procedure for the parking brake and it may be worth going through this just to ensure that this is not the problem. The procedure is as follows:

Ensure the engine is switched off, then disconnect the battery for 30 seconds. Reconnect the battery and start the engine.

Firmly apply and release the footbrake five times. The message ‘Not calibrated’ or ‘Apply foot and parking brake’ should be displayed on the message centre; this indicates that the parking brake is in calibration mode.

Lightly press the brake pedal and apply the parking brake using the EPB switch. Release the parking brake, then release the footbrake. The brake warning lamp should no longer be illuminated and the ‘Not calibrated’ message should have gone. Now apply and release the parking brake five times to ensure that no fault is present.