calys968

Whoever had my T/A before me installed a Granatelli MAF sensor. I bought it in November and it's had the following trouble codes ever since I've owned it...
P0420 Catalyst System Efficiency Below Threshold(Bank 1)
P0430 Catalyst System Efficiency Below Threshold(Bank 2)
P0327 Knock Sensor 1 Circuit Low Input(Bank 1 or Single Sensor)
P0171 System Too Lean (Bank 1)

Then 2 days ago another code showed up...
P0174 System Too Lean (Bank 2)

Is it possible that all these codes could be caused by the Granatelli MAF? If not, what else could they be caused by?

Thanks in advance.

ArcticZee

Do you have an off road y pipe on your car? I have seen cars with bad MAF's that do throw lean codes. It is quite possible that some of the codes are cause by a bad MAF.

calys968

No, my car is pretty much stock except for the Granatelli MAF.
Could my car running lean cause the knock sensor code to show up?
Thanks for your help.

ArcticZee

As far as the knock sensor code goes, the sensor is either bad, or there is a wiring problem with the knock sensor. You should also make sure your MAF doesn't have a vacuum leak before the throttle body, and also check for any other vacuum leaks.