I recently added a voltage booster and subsequently generated a constant trouble code. The voltage booster was added for more pump capacity. There are two sources, Kenne Belle and MSD. I bought the kit from Sean Roe. He takes the MSD kit and modifies it for the Viper. The code that was generated was P0505, that is a malfuction in the Idle Air Control (IAC)motor. There is no circuit association between the IAC circuit and the fuel pump circuit. In addition, the pump was isolated thru a relay. Therefore, it was hard to understand the cause, it was almost as though the two were not related and the code simply only happened by coincidence during the install of the booster.
After about ten hours of trouble shooting with a multimeter and scan tool. I came to the conclusion the IAC circuit was not the cause. That specific code can be set during motor-run or on motor start. I narrowed this code down to the key-on cycle and specifically when the fuel pump cycled, therefore, coming back to the voltage booster again. The power to the relay was fed directly from the PDC post, therefore, this was not a voltage drop issue. I electrically shielded the booster and that did not help. I then fed the booster directly from the battery and the problem stopped. With capacity and radiated electronic noise (EMI) eliminated, the only answer is the high frequency noise created in the conversion circuit was induced into the PCM and generating an error code, it just happended to be an IAC code, it could just as well have been an O2 code.
I know that more than myself have had a a P0505 (IAC) trouble code. It appears that high frequency electronic noise could be the culprit and it is not an IAC issue at all, perhaps this post can shed some light on the problem. I also bought the Kenne Belle booster and I may try it to see if it also presents a problem. A point of interest, if you adjust the voltage to 17.5 volts (at low vacuum), the capacity at the pump is increased about 50%, that probably equates to 30-35% true volume. Both the MSD and Kenne Belle units have regulated outputs which keep the volume constant, which makes the tuning process more consistent.
After about ten hours of trouble shooting with a multimeter and scan tool. I came to the conclusion the IAC circuit was not the cause. That specific code can be set during motor-run or on motor start. I narrowed this code down to the key-on cycle and specifically when the fuel pump cycled, therefore, coming back to the voltage booster again. The power to the relay was fed directly from the PDC post, therefore, this was not a voltage drop issue. I electrically shielded the booster and that did not help. I then fed the booster directly from the battery and the problem stopped. With capacity and radiated electronic noise (EMI) eliminated, the only answer is the high frequency noise created in the conversion circuit was induced into the PCM and generating an error code, it just happended to be an IAC code, it could just as well have been an O2 code.
I know that more than myself have had a a P0505 (IAC) trouble code. It appears that high frequency electronic noise could be the culprit and it is not an IAC issue at all, perhaps this post can shed some light on the problem. I also bought the Kenne Belle booster and I may try it to see if it also presents a problem. A point of interest, if you adjust the voltage to 17.5 volts (at low vacuum), the capacity at the pump is increased about 50%, that probably equates to 30-35% true volume. Both the MSD and Kenne Belle units have regulated outputs which keep the volume constant, which makes the tuning process more consistent.
