# Causes for code P2A00



## MikeGlosta (Sep 26, 2015)

Oxygen sensor
Mass Air Flow Sensor
Wiring
Gas Cap

Are there other areas I can check: This one's got me stumped


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## rogoman (Dec 16, 2004)

The P2A00 fault code is set because of a possible problem with the A/F sensor #1 or circuitry located in bank 1 which is next to the firewall. Here are possible causes:

- Bad Air fuel ratio (A/F) sensor 1.
- Bad Air fuel ratio (A/F) sensor 1 heater.
- Fuel pressure incorrect.
- Fuel injector(s) dirty or leaking.
- Intake system air leaks (vacuum leaks).


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## MikeGlosta (Sep 26, 2015)

Thanks for these suggestions:

I will add injector cleaner; check for vac leaks; clean connections BUT what I'm not familiar with is the A/F Sensor 1 heater: what and where is that?

Thanks


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## rogoman (Dec 16, 2004)

The heater is built into the A/F sensor itself; there are extra wires in the harness for the heater portion. The ECM performs ON/OFF duty control of the A/F sensor 1 heater corresponding to the engine operating condition to keep the temperature of A/F sensor 1 element at the specified range.

To clean the injectors, run some good injection cleaner, like Techron or Redline SL-1, through the system; give the cleaner about a week or two to do it's job. 

To properly test for an intake system vacuum leak, attach a vacuum gauge to a full vacuum source. With the engine fully warmed up, the reading at idle should be 18 - 20 InHg. At 3,000 RPM, it should be around 21 InHg. If readings are under 18 InHg, check the intake manifold nuts to make sure they are tight. The gasket may have failed; spray a water mist at the gasket to see if the gauge reading changes. Also check the intake plenum bellows at the throttle valve and at the MAF for cracks or loose clamps.


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## MikeGlosta (Sep 26, 2015)

Thanks for these pointers. Weather permitting ( the temp might reach 35-40 ) I plan to check the wiring along with hoses and clamps tomorrow. Poured a bottle of Techron into the tank so I'll wait to see what happens.

Note: The car is an 06 Murano, runs as smooth and with plenty of pep as the day it came out of the showroom. I've had the light come on after 10 miles, 75 and 175 - doesn't seem to matter. I'll be looking for a loose connection.


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