The BCM (The inside fuse block) shouldn't have anything to do with it.

If the engine is not runninig the fuel pump will only run for 2 seconds; so checking the voltage without the engine running will not be reliable.

You may want to check the wire colors at the connector, Sometimes GM up an changes the pinout colors. Here is a link that has info about the change.
https://www.chevyhhr.net/forums/how-...acement-36541/

 

The voltage issue occurs upon immediate energizing the circuit...turning on the ignition and I am laying there with the meter. 2 minutes does not elapse....

Is there another cutoff in the circuit that can be bad? For example, my F150 has an accident/impact fuel pump cutoff circuit which may need to be reset in the event of an accident. I have no idea how the wires run from the fuse box under the hood. I have not verified 12V past the fuse or relay plug-in at the fuse box.

 

I don't know for sure. I think it is a straight shot, maybe a connector or 2. Via the body harness.

Anything happening on the floor around the tunnel or the door sills?

 

Looking at the diagram I posted before, the wiring schematic shows a gray wire going straight from the relay to the pump. If you only have 5 volts at the pump, what is the voltage coming out from the gray wire side of the relay ?
If it's 12 volts there then I would suspect a wiring problem between the 2.
Also, did you check the ground connection that I noted in that post ?

 

I meant the pump will run for 2 SECONDS with the engine not started.

The 5V is the 5V reference for the sensors.

There should not be 5V at the fuel pump connector. There is 12V, Ground, gauge signal and low reference (basically ground).

I believe the harness runs along the driver side sills then across under the rear seat frame then out to the axle beam.

 

So Don. Guessing that you mean the OP is checking the wrong wire. The 5 volt should be from the orange/black wire and 12 volt supply should be the gray one.

 

The ground is good for pin-out 3A...checked the continuity there last night.

Donbrew, When the ignition is initially turned on, I am expecting 12V (the primary power for the pump) on at least one of those wire connections coming out of the body-mounted electrical connection/block by the pump...looks like 3C on diagram. None are showing 12V to body ground. I understand that if energized properly, the fuel pump will kick on for a second or two until it builds enough pressure to kick off the built-in fuel pump pressure regulator.

firemangeorge: I have read 5V from at least two of the connectors at the back. I understand that if energized properly, the fuel pump will kick on for a second or two until it builds enough pressure to kick off the regulator. Nothing shows 12V at any of those connection pin-outs, under any circumstances. Didn't expect a sensor on a 12V car pushing 5V into the sensor, but I can take your word for it. I did suspect that could be the case for the sensors.

I think my next step is to unscrew the under-hood fuse box and check the power from the relay wire out (gray in color?) As expected, the primary power supply wire for the fuel pump is colored gray at the rear wiring harness that goes from the body power block/pin-out to the fuel pump. It is also a bigger gauge than the sensor wires, so I am pretty sure we are looking at the correct wires and pin-outs at the back when taking the voltage readings. The ground wire is black and also the same larger gauge.

I'm getting pretty frustrated. Trust me, the thought of running a whole new wire from the hood fuse block/fuel pump relay to the fuel pump has crossed my mind. I wish I knew where every possible connection was along the wiring harness so I can check them. I have seen faulty wiring harness splices from factory connections get corroded and either introduce high resistance or part. Admittedly, this is usually on dirt bikes/quads or really old cars. There has been no wet conditions here (Las Vegas) or anything going on inside where I would expect a damaged wire on the harness.

Keep the ideas coming. I really appreciate the effort.

 

The connector in post #16 does not agree with your reality because it includes a couple of LNF only connections (SS/2.0L).

Also, I didn't bother to point out the bottom diagram and the top connector are mates.

As to 5V, ever hear of computers? Regulated 5V is high reference, low reference is regulated 0 V (technically anything less than 5V, but ground/0V is easier). When you have regulated references, the computer can give a number to an output.

Imagine what the reading would be using a variable 11.5 - 14.5 Volt reference and a suspect ground. How would the computer know what .5 is?

There are no other connections that I know of between the fuse box and the chassis harness connector. Either there is a broken wire or you are measuring incorrectly.

This is the fuel pressure sensor connector an pin out along with the body harness routing, it goes through the sheet metal somewhere and connects to the axle beam etc. You have been under there so I assume you have seen where it emerges.

You could check continuity of the grey wire. Be sure to disconnect both ends.
Pin 3C on the body harness connector should be the pump supply voltage.

 

I got it fixed...I'll share my insights and lessons learned when I get a minute. I did end up dropping in the new fuel pump. I also did bust into the under hood fuse box to chase down the issue which led me to the final answer. We were chasing a ghost and I'll explain why. All the info in this post should be a HUGE help to the next person chasing a HHR fuel pressure or power issues. I certainly learned a ton! THANKS!

 

I guess you don't need this then: