Hello my xjr wont start. It cranks, fuel smells and sometimes it fires but still won't start. It gives 2 fault codes P0122 "Throttle/Pedal position sensor/switch a circuit low" and P1775 "Transmission control module mil circuit"

Maybe crank sensor or tp sensor has failed but is there way to test them or to know exactly which one is faulty?
1996 XJR

 

Disregard the transmission code

Disregard the Camshaft sensor for now as this assist starting but will start with the Crankshaft with more engine rotations .

The TPS will red 0.60 volts DC at idle with the connector on ( check under the TB ) on wire Green / Yellow as it comes over the fuel rail with the key in the on position and not running . Look for a smooth increase of voltage as you twist the throttle by hand , no bibs on the meter as this indicates a bad spot on the sensor

The Crankshaft sensor can fail without giving a code . It will read about 1300 ohms as a fundamental reading with a meter .

The # 1 fuel pump turns on for 4 seconds to prime the fuel rail then off with the key in the on position before start . The fuel pump will turn beck on again when the Crankshaft sensor sees engine rotation through the ECU .

Feel for 3 clicks on the # 1 fuel pump relay on - off - on as the engine rotates in the starting sequence .

You have a # 2 fuel pump on the S/C engine to help troubleshoot later .

See page 79 below : Yours is the AJ16 engine .

http://www.jagrepair.com/images/Trai...20-%202000.pdf

ask questions and someone will help

 

it was maybe just corrosion. Because i opened crankshaft postion sensor connector measured 1218 ohms then i put it back and then i manually turned throttle and car started... it hasn't run almost a year.

 

Yep , it's in a bad environment . So keep it protected with some spray .

Learned how important connectors and grounds are that are neglected .

 

Yeap, do you know anything good spray? I have used oil but i know it isn't that good. I had lots of similar problems with my range rover p38. It didn't charge, airbag light, speedometer, air suspension, tachometer, transmission and lots of other fault just caused by corroded connectors but really funny thing there wasn't any green oxide to be seen, they looked just fine.

 

There is a balance between raw unprotected metal making good contact for a short time before reacting to the environment and turning into a bad contact . Then you can use a protective film that is not always a good conductor across those points of contact but not to good a conductor like water and shorts out your connector .

My personal choice is to work the connector off and on while it's dry to rub off any corrosion in the points of contact then flush out with alcohol then some light spray oil . Then use a DC4 termed dielectric grease ( light bulb grease ) that at least prevents the environment from reacting with the metal . I have changed alot of connectors in my career that were too far gone as well .

Rolls Royce and some connectors on airlines are gold plated to be ahead of the corrosion as it's the least reactive metal .

This is different then connector fluid contamination like on the transmission connector.

Anyone welcome with their recommendations as I'm not always right as this is my first Jaguar

Thanks , Parker , Flight Line Avionics / Electronics Specialist , Trans World Airlines / American Airlines (Ret )