Alero Options not working

[BillSchmidt]

I've got a problem with a 2001 Alero 2 dr 4 cylinder with ~130K. I have been chasing a series of electrical problems and am finally at my wits end.

The car has had the PCM, BCM, Passlock all replaced and reprogrammed by the dealer. Also, I have replaced the main fuse block as well as the one on the left hand side of the dash. The car would not start until the BCM and Passlock were fixed.

The problem that the car is still having is the power locks, power mirrors, power seat, trunk release, and stereo amp (factory) all do not work. When the power lock switch is pushed, you can hear the relay click and the chime. I have checked the ground for these circuits (under the driver seat) and found it to be functioning fine; the wires in the door and under the door sill trim are in tact. There is 12V at the trunk release and at the door lock actuator.

I am out of ideas and so are my buddies. I guess it's time to consult the experts. Help!
Bill

[Tech II]

Hi...I have one question.......were all the options that are not working now, working before the BCM was replaced?

At the power mirror switch harness, do you have power at term E and ground at term D?

Same for power seat switch, power at F and ground at term G?

The locks go through the BCM, and basically, the door lock switches send two different resistances, for up and down.....if they do, and the BCM does not operate the door locks, then it's possible it wasn't programmed correctly....

As for the trunk release, you disconnect the harness to the solenoid, and attach a test light to the harness...if it lights when the trunk release button is hit, you need a new solenoid....

[BillSchmidt]

Thanks, Tech II. The options were not working prior to the new BCM.

I will try the tests that you suggested and report back in the next couple days. Are the connections marked with the letters you mentioned? If not, how can I figure out which connection is which?

Thanks again for the help!
Bill

[Tech II]

The harness connectors are lettered.

[BillSchmidt]

OK, so I finally got the opportunity to do some testing on this thing.

The Power Mirror has 0V at E. None of the terminals have 12V. There is ground at terminals A and B.

The Power seat has 0V at D, and none of the terminals have 12V. There is ground at D.

I went back to the fuse block below the left hand pillar, and checked for voltage at the following fuses: B (Trunk Release), D (Power Mirror), H (Door Lock) and the Power Seat Circuit Breaker. None have 12V. I am thinking I have a problem either at this fuse block, or possibly from the harness.

What do you think?
Bill

[Tech II]

Bill, all those fuses get their power from a 40 amp fuse, LH BEC BATT1, in the underhood fuse block....if the 40A fuse is ok, attach a test light to one of the fuses that are out...take the back of your hand and hit the underhood fuse block to see if the test light flickers....if it does, there are silver screws in the top of the fuse block, tighten them to see if they are loose....

Have seen the screws come loose creating poor connections....if the fuse is blown, it will have to be determined which circuit is causing it to blow, or if there is a rub through condition on the single feed from the 40A fuse....

[BillSchmidt]

Tech II -
Thanks again. The fuse is OK, and there is power at the fuse. I hit the main box under the hood with my hand but the light did not flicker. I assume that is what you wanted me to do?
Bill

[Tech II]

Sorry, I was on vacation......

Yes, that is what I wanted you to do......did you check those silver colored screws in the UBEC to see if they were tight? the three screws to the right of the lower red arrow in the pic below...



If you have power at that main fuse(in and out), and no power at the other fuses in the other fuse box, then you have an open circuit.....more often than not it is at the UBEC(underhood bussed electrical connector), otherwise known as the underhood fuse box....

[BillSchmidt]

Tech II, thanks again. This fuse box you show is a bit different than the one I have. There are three "blocks" that bolt onto the bottom side of the fuse block. Those bolts are tight. There are no bolts on the top like you have shown. (Similar to the one shown here.)


I have a new problem that I just discovered a couple days ago (although maybe it's been there as long as the other problems have been). The headlights do not work - at least the low beams. The passenger high beam does work. There is no voltage at these other three headlight connectors.

This electrical gremlin has got me perplexed.
Bill

[Tech II]

Yes, the blocks install from the bottom side, but the screws/bolts that hold them in tight are on the opposite side.......they could be torx, hex, etc.

If the bolts are tight on the fuse side, and you have power out of the fuse , those other fuses should be getting power, unless there is an open circuit....

You can see that ckt. #442(red wire) comes out of the fuse block from the 40 amp fuse and feeds the door lock, mirror, trunk release fuses.....




As for your headlights, I will have to check those schematics....

[Tech II]

This might help with the lights.....

The same fuse is used for hi and lo(per side), so that is not the problem....

Do your low beams work with the auto headlights at night? If no, do the auto headlights work if you switch to high beams?

You may have an open in ckt #1201, a bad headlight switch, or both low beam lights are bad...

[BillSchmidt]

Thanks again, TechII. Some of the problems are fixed. The root cause was the under hood fuse block that I put in. I was not aware that there was more than one for the Alero, and naturally I pulled one from a car that did not have all of the power options. The original fuse block was re-installed and all of the options started working just fine. I replaced it with one that came from a wrecked car with the same options from the same year.

The problem now is that the engine will not start every time. The fuel pump does not engage and/or the injectors do not activate. Sometimes it will start just fine. There is no rhyme or reason.

Any ideas where to go now?

Thanks.
Bill

[Tech II]

When it won't start, check for spark, fuel pressure and injector pulse....