I finally got my car back on the road after a performance shop found out I had the cam sprocket off one tooth. Anyway's I only had one day of fun with it before it started to sputter on my way home from work. It was a minor hesitation/sputter around 60mph and the SES light came on and stayed on. When I got the car in my neighborhood it started to stutter and hesitate more noticeably. It sat in my garage overnight. Today I drove it a mile to the local Auto Zone and had it scanned. It came up with two codes: P0506 (something to do with the pcm not seeing the expected RPM) and P0155 (malfunction with the oxygen sensor 1 in bank 2). Could either one of these cause my car to run bad? It also started to backfire today which it has never done before. Any suggestions?

 

P0155 = Heated Oxygen Sensor (HO2S) heater circuit Bank 2 Sensor 1

Means either the power supply to the small heater in the sensor is faulty, or the sensor heater is faulty With LT headers, you need the heater to keep the sensors hot enough to work. Would make your car run poorly.

P0506 = Idle system low/Idle Air Control (IAC) valve responding

Your idle speed is too low, and the IAC motor can't contol it. Probably a result of the "sputtering", not the cause.

 

What would be your best guess as to what would cause the P0506 code? I didn't have any trouble with this until I used my air conditioning for the first time. I know the idle drops when you use the A/C.

 

The idle should NOT drop when you use the A/C. The PCM knows when the A/C comes on, and makes adjustments. The IAC valve should open to push the idle speed back up to where it is programmed to be.

As I already indicated, a faulty O2 sensor could cause the sputtering problem, and the sputtering problem may be causing the idle problem.

For some reason, the IAC motor can't control the idle. IAC passages or IAC motor could be dirty or plugged. Throttle stop may be incorrectly adjusted. IAC motor might not be working. A "scan" would allow you to observe how the IAC motor responds to the idle problem.

First fix the problem with the O2 sensor heater circuit. Eliminate one problem at a time.

 

Thanks Injuneer. That really clears things up. The O2 issue should be fairly easy to fix. I'll check the voltage at the connector before I buy a new O2 sensor.