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Then you probably have loose connections on individual pins within the connectors and not with the BCM itself.

What do you mean by "reseating" the BCM?

Also consider using a Motive type pressure style bleeder.

I think Bosch is considered about the worst for GM. Typically GM and Ac Delco are considered to be about the same. I think the experienced guys on GM section of HPT also say that NTK also work for GM but I could be wrong and it’s NGK or Denso is the other brand they recommend. I doubt that this...

While Ross isn’t totally wrong, the voltage on narrow band o2s are actually a lot tighter than 0 to 5. I don’t have a service manual for your donor but I’m pretty sure all GMs use the same control strategy. My 2010 Camaro manual states that voltage is supposed to be 0 to 1275mV.. But these...

We really probably should have had you do a visual inspection of all connectors and pins related to the issue as the very first step. It's just hard to not jump into the full diagnostic mode.

The PCM side of the C1 connector. All three of the 5v reference 2 feeds connect to the same transformer inside of the case. The C1-30 connection inside of the PCM is looking like it has failed. It could be at physical connection to the pin or in a trace on the circuit board. There is a chance...

About the only thing that might be related to the current issue, is that during the removal of the fuse box (and I assume the PCM) you pulled on an already failing C1-30 pin connection inside of the case that caused it to fail completely.

Ross is trying to get you to check continuity between c1-30 and C2-9, not whether either of those is grounded. I would check with the ECM completely disconnected and measure on the pins of the ecm itself. They should connect up inside the ECM, although you are getting outside my knowledge on...

Have you looked up thee wiring diagram and pinouts from a real source for your donor? That should answer all of your questions.

About the only thing left is the pressure plate but I can’t say how it would fail like that or how to test it.

Did you look at any of the diagrams to see if you have 5V on the correct wire coming from the 5v Ref#2? The secret to doing electrical diagnostics is to pay attention to details. But it is starting to sound like a failure of the 5v reference 2 bus inside of the ecm.

Do you get 5V on either of the other sensors? If not, time to check and see if any of the 5v Ref2 feeds to the sensors are shorted to ground. With the sensors and the PCM disconnected check for continuity to ground of the C1 30 wire and the other 5v ref 2 wires to the sensors. Should be able to...

So it's time to unplug the Tac module and Map sensor and see what you get. Diagram in post 98 says that is the 2 other sensor on 5v Ref #2.

Connector end views are of the wiring connector, not the sensor they are being plugged into. If there is pigtail on the sensor, then you need to look at the pictures real close to confirm which connector you are looking at. But you should have 5v on two wires coming in anyway. Were the voltages...

The "near Ref" might have to take into account the pull up/down voltage that most of these circuits use so the ECM can have a voltage to check the wiring. Maybe it has 1 volt when at rest? But that is just a guess. Picture in post 115 says Pontiac G5 at the top so that is the base Cobalt, if...

Nail the brakes and see which ones lock first?

Two spots of the TAC harness could mean 5v on the feed side and 5v on the signal side if this sensor puts out 5v at no throttle. I assume this TAC works by increasing voltage on 1 sensor and decreasing on the other. Captain Dave, give us exact pins and names as shown in Ross's wiring diagram...

Use the names, Use the names, pin# and Connector # as shown on a posted wiring diagram. That way we can all be sure that we are all talking about the same thing.

And remember that if we can't see whatever wiring diagram or pinout you are looking at if it's not posted here. We don't have all of this stuff memorized.