Guys,

I’m beyond frustrated with this Equinox. I have replaced, ECM, TBA, coolant sensor, plugs, 02 sensors, accelerator sensor (gas pedal) and a few
other sensors on top of the engine. When I start the car, it idles great between 700-800, and will idle like that indefinitely. As soon as I put the car in gear and start moving, the idle goes to 2k plus and won’t go back down. Then I get the dreaded “reduced engine power” service stabilitrack, etc. It will not reset unless I disconnect the neg terminal for 15 or so
mins. I cannot figure this out. Occasionally it will throw the codes p0641, p0532 and p0507. These codes don’t always show on the scanner. I have traced all the wires and cannot find any break, or exposed wire. I’m lost guys. I have been at this for 2 weeks now. Someone said it could be the Onstar, but I read to never disconnect it. Please let me know what you think, and if it’s happened to you before. I’m defeated guys. Thanks!!!

 

Common Problems That Trigger the P0507 Code

• Defective/sticking Idle Air Control Motor (IAC)
• Intake Manifold Vacuum leaks
• Carbon buildup in the Throttle Body air passages
• Defective Coolant Temperature Sensor
• Defective Charging System/Alternator
• Defective Power Steering Pressure Switch

I'd go for a bad IAC myself. Does your motor run rough? Wouldn't hurt to torque down your intake manifold either.

 

I'm thinking you have a wiring issue somewhere. Try unplugging the refrigerant pressure sensor in the discharge hose that goes between the compressor and the evaporator, and see what happens. If the engine runs fine with it unplugged you've at least narrowed it down to that circuit. SI seems to indicate you may have an issue with bus one of the 5 volt reference either being open or shorted to ground. The refrigerant pressure sensor and accelerator pedal position sensor use the same bus.

 

A little FYI,
The PCM is supposed to supply a 5 volt reference voltage to most of the sensors in the vehicle..
When things are right different sensors will alter this voltage and send the voltage back to the PCM as a signal voltage.
Here is where it gets a little hairy,
If for any reason ,
there is no 5 volt reference voltage available to the sensors involved, the PCM will pick that up as incorrect signal voltage and possibly throw a code showing the system involved.
One way to chase this down is to start at the PCM and see if the 5 volts is available there.
If it is then we need to find why and what is pulling that voltage down . It could be a grounded wire rubbing through someplace, a shorted sensor or possibly a break in the wire to the affected sensor(s). This is not something for an inexperienced person to become involved with. A wiring diagram is a necessity here and needed to know which sensors are on the circuit for tracing to be done. You could spend weeks and never find the cause. Best to have an experienced shop/person chase this down for you. I would seriously consider some experienced assistance from someone that knows and understands voltage drop testing and has the info and equip to do it.

 

One problem known to affect the TAC system is corroded connectors due to water intrusion. Although technically the P0641 should be addressed first since it could cause the other codes to set (as well as result in reduced engine power), it may be worth it to inspect these connectors anyway as water intrusion could be shorting the 5 volt reference to ground.

The first one is in the engine bay on the passenger side - the other is under the driver side of the dash. I circled the connectors in red.