fault code FF 15
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Joined: Oct 2008
Posts: 1,930
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From: San Jose, CA, USA
air temp sensor voltage out of range.
The air temp sensor is on the left hand / drivers side air intake just in front of the air filter housing. Its in quite an exposed location and the connector is easily dislodged so thats the first place to check. The connector should snap or click home.
While you are investigating this, its a good idea to fully check your OBD I system is working properly, because its very easy (and common) for these useful systems to be disconnected on these cars. Note the system is NOT OBD II, so anyone that says "just get a scanner to read the code and clear it" is wrong.
You say you briefly saw the fault code on the trip computer......... if you have a true fault, this is what should happen.
1. Turn the ignition key on, but don't start the car. If you have a real fault, you should see the fault code being displayed on the trip computer. You should also see the words "Fuel failure" on the trip computer screen, just above the FF code. The check engine light on the instrument cluster should also come on and stay on.
2. Start the car. The Check engine light will stay on. The "Fuel failure" wording will remain lit on the trip computer, but the FF code will now disappear and the clock comes back on.
You need to clear the code, even if you fixed the fault and its no longer there anymore. The easiest way is to disconnect the battery for 60 seconds then reconnect. There is another way to reset the code without disconnecting the battery, but it is a bit more involved and requires you to take some trim parts off around the center console.
Let us know how you get on with your investigations
The air temp sensor is on the left hand / drivers side air intake just in front of the air filter housing. Its in quite an exposed location and the connector is easily dislodged so thats the first place to check. The connector should snap or click home.
While you are investigating this, its a good idea to fully check your OBD I system is working properly, because its very easy (and common) for these useful systems to be disconnected on these cars. Note the system is NOT OBD II, so anyone that says "just get a scanner to read the code and clear it" is wrong.
You say you briefly saw the fault code on the trip computer......... if you have a true fault, this is what should happen.
1. Turn the ignition key on, but don't start the car. If you have a real fault, you should see the fault code being displayed on the trip computer. You should also see the words "Fuel failure" on the trip computer screen, just above the FF code. The check engine light on the instrument cluster should also come on and stay on.
2. Start the car. The Check engine light will stay on. The "Fuel failure" wording will remain lit on the trip computer, but the FF code will now disappear and the clock comes back on.
You need to clear the code, even if you fixed the fault and its no longer there anymore. The easiest way is to disconnect the battery for 60 seconds then reconnect. There is another way to reset the code without disconnecting the battery, but it is a bit more involved and requires you to take some trim parts off around the center console.
Let us know how you get on with your investigations
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philwarner
XJ XJ6 / XJ8 / XJR ( X350 & X358 )
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Jun 26, 2021 05:43 AM
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