A couple of weeks ago, with the car turned off, keys out of the ignition - about every thirteen seconds you could hear the air injection pump coming on, running for a couple of seconds and then turning off. The next day the car battery was dead (no surprise) so we charged it up and took it to the shop (AAA) . They told us that it was a faulty MAP sensor and didn’t give us a price quote to fix it, just an invoice/diagnostic bill. But they did unplug the air injection pump so that the battery wouldn’t keep getting drained. We drove the car home and called them the next day to get an estimate for the repair and they said that they misdiagnosed the problem and that it was actually a MAF sensor that was causing the air injection pump to come on when the car was turned off and that it would cost around 500 dollars for the part and labor. Too steep so we decided to hold off on the repair. Understanding our reluctance to go through with the repair, they recommended that we plug the air injection pump back in and still drive the car but to make sure that we unhook the battery at night/when the car would be sitting for many hours without being started.
Here’s where it gets a little confusing (or at least for me). I did take AAA’s advice and went ahead and plugged the air injection pump back in and for the last couple of weeks it’s been fine. No issues with the battery being drained whatsoever/no air injection pump coming on with the car turned off. But today the air injection pump started doing its thing again.
The check engine light was on so I hooked my code reader up and pulled the following codes:
PO128 (thermostat coolant temp below regulating temp)
PO491 (secondary air injection system (Bank 1)
PO2431 (secondary air intake system FLW/Perf B1
So what do you guys think? Does all this point to a faulty MAF sensor?