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1996 GMC Suburban 7.4L Engine Reving in Park/Neutral with P0507 and P1509 Codes

Model: 1996 GMC Suburban Fault Code: P0507 Posted: 2014-01-20 13:56

I've been experiencing recurring engine revving issues on my 1996 GMC Suburban with a 7.4L V8 engine. The vehicle consistently runs at 1500 to 2500 RPM when in park or neutral, while in drive it maintains a stable idle between 1250 and 1500 RPM during stoplights. I've already replaced the Idle Air Control (IAC) module multiple times, upgraded the Mass Air Flow (MAF) sensor, and had the throttle body professionally cleaned. A vacuum leak test was also performed and returned negative. The PCV valve was replaced two years ago. Despite these efforts, the fault codes P0507 (Idle Control System Malfunction) and P1509 (Fuel Pump Control Circuit Issue) persist. Has anyone encountered this specific issue on a 1996 GMC Suburban? What steps did you take to resolve it?

Related fault codes
P0507P1509
Comments (2)
Anonymous 2014-01-21 08:29

Did you source your IAC valve from the dealership or an aftermarket brand? Some IAC valves are designed for specific engine applications and may not perform optimally in older GM trucks like the 1996 GMC Suburban.

Anonymous 2014-01-21 10:46

The most straightforward diagnostic step is to use an OBD-II scanner to command the IAC valve directly. This will help determine whether the idle control system is responding properly under PCM commands, and can identify if the issue stems from wiring or faulty IAC operation.