Why would installing a K & N CAI kit cause check engine light to come on

You buy service repair info. (manual) an do the diagnostic procedures for those code's . Which include testing the electrical circuit's . or view video's on youtube showing how to diagnose .

YOU HAVEN"T DIAGNOSED ANYTHING YET ! YOU READ CODES ,THAT'S ALL
I have diagnosed my 2001 Nissan xtrail with 2 errors: P0102 mass or volume air flow circuit low imput & P0113 intake air Your best bet , take it to a qualified repair shop.

p0102 is your Mass Air Flow device.
p0113 is "air intake temperature" sensor voltage too high.
p0171 is "engine running too lean"
p0300 is "random misfire"

You can pretty much ignore your p0113, p0171 may be caused by a bad MAF, and p0300 may be caused by your p0171.

the actual indication for your MAF is that the voltage getting to the computer from the MAF is too low. It could be a bad MAF, or bad wire between the MAF and the computer.

http://www.explorerforum.com/forums/showthread.php?t=228242

This shows list of codes. You have so many faults hard to know where to start. Was new engine an EXACT match for the old one? If not, did you change ECM? Appears MAF is not connected or bad, and also #1 injector circuit is bad. Others also.

K & N is the number one killer of mass air flow sensors the oil gets burnt onto the fine wire and takes several cleanings to remove this film and the best sensor cleaner just aint good enough for one cleaning.

Using Google-- is how you look up OBD Codes

Problems & some solutions

Type:OBD PO102

Codes DO NOT mean you replace parts

They have nothing to do with parts
UNTIL the vehicle is properly diagnosed
& a PROBLEM IS FOUND

Here's code P0102.Here's code P0113.Here's code P0171.

My P0102, P113 codes turned out to be the connector to the mass air flow sensor - wasn't all the way on.

The common faults on this engine are EGR valve and IAC valve.
The EGR causes rough running and cutting out,
The IAC causes just cutting out without the rough running, stalling at junctions etc is the usual complaint.
If you pm me the cars reg, chassis no etc i could see if i could email you the manual its a pdf so should be quite straight forward.

P0102 OBD-II Trouble Code - Mass Air Flow (MAF) Circuit Low Input

What does that mean?
Basically this means that there is a problem with the Mass Air Flow (MAF) sensor or circuit. A more technical description would be that the MAF circuit had lower than expected voltage (air flow). Other MAF sensor circuit DTC trouble codes are P0100, P0101, P0103, and P0104.

Symptoms
You will likely not notice any serious drivability problems, although there may be symptoms such as a general decrease in power or sluggishness.

Causes
A code P0102 may mean that one or more of the following has happened:
* The MAF may be disconnected, or a wiring connection may be bad
* The MAF may be dirty or otherwise contaminated (Note: if you use a reusable oiled air filter, be careful not to apply too much oil or that can contaminate the MAF).
* The MAF sensor may be faulty
* The vehicle computer may be faulty (very rare)

Possible Solutions
The simplest thing to do is to reset the code and see if it comes back. Then start with the cheapest, easiest repair procedures:
* Verify that the Mass Air Flow Sensor wiring is connected properly and that there are no broken / frayed wires.
* Inspect for any air leaks near the MAF sensor.
* Take the MAF out and clean it using a spray cleaner such as brake cleaner or electrical contact cleaner. Be gentle with the sensor.
* Check the voltage of the MAF sensor (refer to a repair manual for vehicle specific information)
* Replace the MAF sensor.


P0113 - Intake Air Temperature Circuit High Input

What does that mean?
The powertrain control module (PCM) monitors the temperature of the air entering the engine. The PCM supplies a 5 volt reference voltage to the Intake Air Temperature (IAT) sensor. The IAT is a thermistor that varies resistance based on temperature. As the temperature increases, resistance decreases. Low temperature results in a high signal voltage. When the PCM sees a signal voltage higher than 5 volts, it sets this P0113 check engine light code.

Potential Symptoms
There will likely be no symptoms other than illumination of the Malfunction Indicator Lamp (MIL - Check Engine Light / Service Engine Soon).

Causes
A code P0113 may mean that one or more of the following has happened:
* Internally failed IAT sensor
* Faulty connection at IAT sensor
* Open in IAT ground circuit or signal circuit
* Short to voltage in IAT signal circuit or reference circuit
* IAT harness and/or wiring routed too close to high-voltage wiring (e.g. alternator, spark plug cables, etc.)
* Faulty PCM (less likely but not impossible)

Possible Solutions
First, if you have access to a scan tool, is there an IAT reading? If the IAT reading is logical then the problem is likely intermittent. If the reading is less than -30 degrees, unplug the connector. Install a jumper wire between the harness connector signal and ground circuits. The IAT temperature reading on the scan tool should be maxed out at the high end. For example it should be 280 degrees Farenheit or higher. If it is, the wiring is okay, and it may have been the connection. If it isn't install the jumper wire between the IAT signal circuit and the chassis ground. If now the IAT reading on the scan tool is maxed out then check for an open in the IAT ground circuit. If you get no reading at all on the scan tool, it's likely that the sensor signal is open or the 5 volt reference is missing. Check using a DVOM (digital volt ohm meter) for a 5 volt reference. If it's there, then unplug the connector at the PCM and check for continuity on the IAT signal circuit between the PCM connector and the IAT connector.

I really hope help with this (remember rated this).

At this point you need to test the signal from the MAP to the PCM (powertrain control module), it should vary between about 1 and 4 volts as you throttle the engine up and down quickly, if little or no change then the heated wire in the MAF is burned out and th sensor will have to be replaced, in that case, they sell rebuilt units at a very reasonable cost, try rockauto.com, best prices around period.