07 chevy equinox p0641

Alright this is my last resort before I take it out in a filed with a can of gas and burn it down. Lol j/k but don't think I haven't thought about it!
History:
No issues, I've had the car for 7 years and only had to do standard maintenance, tires,plugs,wires brakes, a alternator etc. Standard stuff. Got the code about 3 months ago with no accompanying code, I park and start it up in the morning and it's gone. For about 6 weeks then I get it again, goes away for a week, comes back, goes away and about 3 weeks ago it's now constant. Still with no accompanying codes. But my ac was clicking in and out, so I checked the switch( which this model has a single hi/lo switch right next to the compressor) as I try to unplug it, my ac kicks in. Boom, run up to autozone grab a ac switch, replace it and all good. 2 weeks go by with no code and then it comes back. This time the ac works and I get a map sensor code. I go grab a map sensor and the code does not go away( I broke the map sensor during removal so I couldn't take it back lol) after check all my wiring I plug a multimeter into the map plug and it shows 3v so I start wiggling the wires behind the plug and it's dropping to 0. Go grab a plug and replace it. Still 3v and still p0641 but no variation on multimeter anymore.

Now...
Now I spent an entire day under the hood and under the motor when it was on ramps and could not find a single rub spot anywhere. I go online and buy access to the full manual (I can't remember the name) but it has all the wiring diagrams,sensor locations, replacement steps etc. I find out there's 5 sensors on that 5v ref circuit. So I unplug and check each one individually all get 3v instead of 5v. Now when I hook up the multimeter and turn the key on, they get 5v for about 4 seconds, then it immediately drops to 3v, light on, reduced engine power etc. There's only one sensor I haven't checked and that's the fuel tank pressure sensor. The reason is this model has the octopus fuel pump assem. Where everything is all in one and on top of the tank. I even tried clipping the wire going to the sensor to see if the ecu is putting out 5v and it is NOT..with the map sensor wire clipped (only leaving about a 3 inch tag direct from the ecu) I'm only getting 3v.

Now after the short book lol my question is..will a short in one sensor wires cause all sensors in that ref circuit to drop? Is that why even with the wire clipped I'm only getting 3v?

Also I bought an ecu thinking that might be the issue but I can't get it to program. I gave them my vin and it will not work.

Also my current codes are p0641 and p0106. I checked the resistance on my map sensor with OL tester on multimeter and get a beep with 0.8 ohms. I check my a/c switch,egr and ict.

Secondary question that is likely irrelevant but I'm interested to know, the signal wire for the map sensor and ect connect together underneath the plenum and go to ecu. How the hell does that work?

Hey Maadpotter! For everyone else following along, I grabbed a few bits of service info:

Now after the short book lol my question is..will a short in one sensor wires cause all sensors in that ref circuit to drop? Is that why even with the wire clipped I'm only getting 3v?

The short answer is yes - A resistive short on any single 5V Reference 1 circuit (6259, 2704, 5047, 2700, 2709 or 1274) will cause the reference voltage to be low to all of them.

I say resistive short because it's not a dead short. Otherwise, your measured voltage would be zero. That makes your job a bit tougher, as you're now also looking for things like green corrosion and water intrusion.

In this case, I think I'd stick to Paul's approach. Key on, measure 3V on your disconnected MAP sensor. Find another 5V Ref 1 sensor and unplug it. Turn the key off for 10 seconds, then turn it back on and recheck. No change? Leave the last sensor unplugged and unplug another. Key off 10 seconds, key on, recheck voltage. Repeat until everything but the FTP sensor is unplugged OR the voltage comes back.

Secondary question that is likely irrelevant but I'm interested to know, the signal wire for the map sensor and ect connect together underneath the plenum and go to ecu. How the hell does that work?

Are you talking about S106?



That's actually a shared sensor signal ground between the MAP and the ECT, not the signal wire. That can be a bit confusing, as those are the only two sensors that share a ground on this vehicle. All the other sensors have their own exclusive ground circuit (again, on this vehicle).

Maadpotter wrote:

Also I bought an ecu thinking that might be the issue but I can't get it to program. I gave them my vin and it will not work.

Did you try plugging in the new ECM to see if it gets pulled down to ~3V? I doubt it would need programming to power the Vref circuits.