Jaguar S-Type Restricted Performance
On the petrol S-Type, Restricted Performance or Engine Failsafe Mode usually comes from the drive-by-wire throttle — either the throttle body itself or the sensor in the accelerator pedal — or from a failing ignition coil. The fault often stores no code, so I'd note exactly when it happens: at cruise, at idle, or in the wet. On the 2.7 diesel I'd look first at the particulate filter and the air filter.
How bad is it · Garage, carefully
Drive gently to a garage, and not at all if it cuts out
A throttle fault can stall the engine without warning, even mid-corner. On the diesel, a rising oil level means fuel in the sump, and the engine can run away on it.
Which one applies to yours depends on your symptoms, your model year and what has already been done to it.
Likely causes, most common first
Read the check cost before the odds: a free check that rules a cause out beats a likely guess that costs money.
A faulty electronic throttle body
The throttle is opened by a motor, not a cable. When its angle reading goes wrong, the engine computer drops into failsafe and caps the power.
Shudder and short rev drops every few seconds, an erratic idle, loss of pull at a steady cruise, the occasional stall, and the failsafe message. New coils may help for a while, then the fault comes back daily.
Read the codes for a throttle angle fault. If it is still there after the coils and plugs are new, the throttle body is next.
Replace the throttle body. A dealer unit is expensive — about £1,300 has been quoted — so a remanufactured one (around £200 plus VAT in exchange for the old one) or a good used unit is the cheaper route. When refitting, note which pipes are breathers and which carry coolant: swapped, they draw water into the inlet and can break a connecting rod.
A failing ignition coil
A coil that breaks down under load misfires briefly; the engine computer sees the misfire and switches to its emergency program before a code has time to set.
An orange warning and the engine emergency program message at 50–70 mph with a slight misfire, which then clears. Worse in heavy rain or after power washing the engine.
No stored code does not clear the coils. Look for damp in the coil wells; the left-bank coils on the V6 are the easy ones to reach and the ones most prone to damp.
Replace the failing coil, or the set if more than one is suspect. The right-bank coils take more work to reach.
2.7 diesel: fuel in the sump
A sticking valve can let diesel into the sump. The engine can then burn its own oil as fuel and run away, revving into the red even out of gear, until it stops.
A dipstick reading well above normal; the engine accelerating on its own; later a knock.
Check the oil level on the dipstick whenever the diesel goes into reduced performance. A level that has risen, or oil smelling of diesel, means stop driving.
Caught early, find the leak and change the oil. Once it has run away and knocks, the engine has to be replaced.
The accelerator pedal position sensor
The pedal tells the engine computer how much power is wanted. If its two signals disagree, the computer stops trusting the pedal and goes into failsafe.
Failsafe at a steady cruise but never at idle; sudden cut-outs while driving; sometimes a slightly uneven cold idle. A code for the pedal position sensor may be stored.
Read the codes and look for the throttle pedal position sensor. Live data from the pedal, pressed slowly from rest to the floor, should rise smoothly without drop-outs.
Worth trying before a throttle body: the pedal sensor is a ten-minute swap at the dealer.
2.7 diesel: a loaded particulate filter, a blocked air filter or turbo calibration
The diesel limits power when the particulate filter is full of soot or the engine can't breathe. The engine computer can also flag Restricted Performance in error when one of the two turbos spins up slower than the other.
Restricted Performance after about 15 miles, worse in slow traffic; switching off clears it, but it returns within a few hundred yards. Often no fault codes are stored.
Give it about 20 minutes above 40 mph so the filter can regenerate. Look at the air filter: it is due at 36,000 miles but often clogs sooner.
Worth trying: a long run for the filter; if it won't clear, a forced regeneration at the dealer. Ask the dealer about the bulletin that reprograms the engine computer for the slow-turbo warning.
The order to check them in
The point of the order is money: each step either rules a cause out or makes the next one worth doing. Green is free, amber costs a little, red is the one to arrive at last.
Read the codes
Look for a throttle angle, pedal position or misfire code. An empty reader is common with this fault and doesn't mean the car is healthy.
freeNote when it happens
At cruise but never at idle points to the pedal; shudder at idle as well points to the throttle body; in the rain or after a wash points to a coil.
freeDiesel: check the dipstick
If the level has risen or smells of diesel, stop and have it recovered.
freeDiesel: a long run and the air filter
About 20 minutes above 40 mph to burn off the soot, and a look at the air filter. If the message keeps coming back, the dealer can force a regeneration and update the engine computer.
a filterPetrol: the coils
Dry the coil wells and replace a suspect coil. If the message returns daily with idle shudder, move on to the throttle.
one coil, or a setPetrol: the pedal sensor, then the throttle body
The pedal sensor is the cheaper part and quick to fit. A throttle body is the bigger bill — price a remanufactured or used one before a dealer part.
pedal sensor, then throttle bodyGearbox Fault on the dash as well?
On the V6 and V8 petrol cars the gearbox is a Ford 5R55N. Have a transmission specialist read it first: a rebuild there costs far less than a dealer gearbox.
specialist diagnosisWhat it usually isn't
Don't spend money here first:
If none of this finds it:
On jagaux.com
- Jaguar S-Type MisfireIf it judders on light throttle and a cylinder code is stored, or there is water in the boot.
- Jaguar S-Type Gearbox Fault, Transmission FaultIf the dash shows Gearbox Fault along with the power loss.
- Jaguar S-Type Rough IdleIf the idle is rough but the car pulls cleanly once moving.
- Jaguar S-Type DSC Not Available, ABS FaultIf DSC Not Available or ABS Fault shows with the power loss, or the traction light flashes.
- Jaguar VIN decoderConfirm your exact model year, engine and factory options before ordering parts — free.
Ratings, fuse numbers and torque figures vary by model year and market. Read the legend on your own car before pulling anything, and use the figures in the manual for your car, not the ones in a video.
Check your VIN: exactly which car you have and which bulletins apply to it.