weather calls Jaguar tools to action
sight of a fault warning message at 70mph can be very concerning,
and an owner embarking on a 5 hour motorway trip in a 1999 Jaguar
S-Type had exactly that problem recently - about an hour into the
Accompanying the warning message was an uncomfortable 'jolt' from
the engine and jump in fuel consumption.
The fault message was displayed for a while, then would disappear for
a few minutes, then reappear - accompanied by another jolt. This continued
for most of the journey, until the fault was being displayed permanently.
the dashboard was reporting a 'Failsafe Engine Mode' message, the Check
Engine light wasn't on - indicating that this wasn't a 'major' engine
fault. Scanning with a generic EOBD scanner showed no fault codes (understandable
given the engine fault light wasn't on).
But once the Jaguar
Enhanced AutoEnginuity tool was connected, the fault became
fault code report was showing 'Pedal Position Sensor Disagreement
Between Sensors' - pointing to a problem with the sensor unit
on the throttle pedal.
is a 'black-box' unit on the throttle pedal assembly, which houses
3 separate sensors to monitor the position of the pedal (pictured
on the right).
fault was confirmed by watching the graphs from the individual sensors.
Their outputs were all changing as the pedal was depressed, but
there were inconsistencies appearing almost at random.
A repair didn't look possible, so a replacement was probably the
spending any money, the first job was to check the wiring to the pedal
sensor unit. Connections seemed firm, but on disconnecting the wiring
and removing the pedal, part of the problem became clear. The contacts
within the connector appeared slightly corroded.
We began to suspect what might have caused the issue: the British wet
was returning from a very wet week in the Lake District - having had
people jumping in all week in wet clothes.
As the connector to the pedal assembly didn't have a firm seal, moisture
in the car seemed to have condensed on the connectors, causing the corrosion.
After cleaning the connectors, the pedal was now working much more reliably,
but was still intermittently triggering the same fault. Checking the
graphs, the readings from the 3 individual sensors seemed better, but
we were still seeing a few random inconsistencies.
spending the £150 on a new pedal sensor unit, it was decided
to try drying the sensor on a radiator overnight to make sure the
moisture wasn't causing any further problems.
The following day, the pedal was refitted and was back to perfect
working order. The fault code was again cleared and hasn't returned
repair: a little time investigating and £0 on parts. Owner very
Amazing that a wet British week was probably the cause of this fault.
With all this rain, I'm sure this won't be the last weather-related
fault we'll hear this Winter.
More details on the AutoEnginuity
Jaguar package can be found here.