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Richard, Jaguar Technician
Category: Jaguar
Satisfied Customers: 15545
Experience:  12 years at a Ford/Lincoln Mercury and Jaguar dealer as technician and shop foreman.
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Jaguar X-Type The battery light on my 2005 X-Type Jag comes

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The battery light on my 2005 X-Type Jag comes on when driving about half the time. The OBDII code is P1111 which translates to Intake Air Temp Sensor Intermittent High Voltage. Does this mean that the sensor is causing the high voltage issue or that the alternator is sending to much current? What do I fix? and Where is the IAT? Can i change it out or is it part of the MAF or is something else the cause?

Hello and welcome to


WHen the battery light comes on this means there is a problem with the charging system and usually not an engine management problem. The code P1111 is a readiness code in which there is no repair needed and it does not need to be cleared. The battery and alternator should be tested. I also see issues with the battery cables causing this.

Customer: replied 6 years ago.
Carmax claims that they tested the charging system several times and could find nothing wrong. Meanwhile the battery died last weekend and I had to have it recharged at Autozone. How do I figure out what the problem is so I can fix it?
A digital voltmeter is needed to check this. We need to check the charging system voltage with a digital voltmeter with all accessories on to see if the voltage drops at the battery terminals then check it at the alternator power lug. If the voltage remains above 13.5 then this may be a problem with the cluster. You may even see around 15 volts which is normal. If the voltage is below the 13.5 then I suspect a problem with the wiring to the alternator or that negative cable. We need to check this when the warning light comes on. we can put the instrument cluster in engineering mode to see what voltage the cluster is seeing. First turn off the engine. Press and hold the trip button in the turn signal stalk then start the engine while holding the trip button. You will see the instrument cluster go into engineering test mode. Release the trip button then keep pressing it until the voltage reads a digital number.
Customer: replied 6 years ago.
One last question. I held the trip button and started the car. I did not see the instrument cluster do anything digital. The only thing digital is the odometer and it didn't look any different then normal. Am I missing something?
IT should say engineering test mode. Try it again and keep holding that trip button on the turn signal switch.
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