So I have an '03 XJ8, and it just threw a P1121 on me. Note its p1121 only (besides the p1111 or p1000 code it threw after I cleared codes.) No 16XX codes like you usually see.

About 7k miles ago I replaced the throttle body with a JayTan rebuilt one, so I am not in a rush to blame the TPS just yet. I checked all the fuses, none blown. Anything you guys can tell me?

 

Well if it is not the TB, it would seam it is a bad wire or connector. Try looking at the connections for corrosion, then clean well with contact cleaner and reseat.

The JTIS diagnostics say:
Pedal position sensor to ECM sense
circuits 1 and 2 open circuit, short
circuit or high resistance

Sensor power supply fault

Sensor reference ground fault

Pedal position sensor failure
Good Luck

 

P1121 isn't the TPS but the TPPS (throttle pedal position sensor) on the other side of the tb - this is more likely worn out if not replaced - if it keeps doing it, gradually getting shorter between restricted performance it'll need replacing.

 

As long as none of the PS are available as spare, probably in these cases is more indicated to recommend a full refurb of the throttle body. I assume that they are changing both during the refurb process... or not? Anybody can guarantee this?

Is the car a X308 or X350?