Bill Curlee

There are ONLY TWO fuse boxes in the C5. Under Hood and Passengers Foot Well.

The BCM has MULITIPLE FUSES. You MUST,,, check the VOLTAGE on each FUSE to insure that you have FULL battery voltage on each fuse.

WHAT DTCS do you have???????

CHECL ALL of these FUSES and the GROUNDS!!

99 Schematic.

CKCars

Bill, Many thks for the paperwork...

The BCM Fuses in my understanding our in the cabin area passenger side. the located at 9, 22, 23 and 25. The voltage is 3.2 volts because of the short as presented when the blue harness is connected. My guess would be if I unplug the Blue harness... the feed on the fuse box will again read 12V. I keep thinking we might have to figure why we get a voltage drop from 12V to 3.2 when the feed is reconnected to the top of the fuse box. (Blue Harness)

???Question. Did my pictures show-up in the post...

And also why we have a good 12V in the cabin fuse box... only if the top blue wire harness is not attached...

Elect Problems... not my Fav... Keep helping me Friend.

In REGARDS: WHAT DTCS do you have???????

I have the Fuse Box out of the car at this time... so I can't see the codes at this time. I do remb... Service Engine and Low Fuel... But I did'nt have low fuel. I thought it's saying stuff because of low voltage... but maybe I'm wrong.

Bill Curlee

ANY,,,,,,,,,,,,,,,,,,,,,,, Circuit that reads something that LOW when connected to a LOAD, tells me that the IGNITION SWITCH supplied circuit is compromised.

It IS NOT shorted or you would see a BLOWN FUSE, SMOKE or FIRE.

The #13, #9 and #22 FUSES come from an IGNITION SWITCH source. The contacts inside your ignition switch are most likely BURNT/damaged!

I highly recommend getting a new ignition switch or servicing your switch.


Bill

CKCars

Bill, Would I have low voltage to the under dash fuse box... even if the ignition switch is bad??? Would the grounding out of the Fuse Box cause the IGN to fail also??? and reduce the voltage back to the fuse box??? If so, that would lead me to think the blue harness is someway connected to this loop. Does anyone have a drawing of the harness as related to the blue connection and fuse box. That would be helpful.

Bill... am I allowed to accept a phone call from a member... sure would save me my typing skills... which I have none of...???

I'm not the sharpest cookie cutter... but surly I can make this fix and move on...God I hope!

GCG

Just to double-check I understood it: you're saying that voltage at the yellow circled point in the picture below drops to 3.2v when blue harness is connected?

Bill Curlee

Can you move either of the battery terminal cable connections by hand?

If you turn the head lights ON, what does that B+ terminal on the under hood fuse box read? What does the Foot Well B+ terminal read?

Bill

GCG

Exactly! It seems there's a significant voltage drop at some point between the "+ battery post" - "under hood fuse box B+ stud" - "passenger fuse box B+ stud" path. Either that, or the battery is toast.

What is the battery voltage directly at the battery posts? What happens to the voltage if you turn on the headlights? It might be a good idea to have your battery load-tested at an autoparts.

If your battery tests well and is fully charged, I would thoroughly clean and re-tight all contacts along the path mentioned above as a first step.

MrLeadFoot

Guys, remember that the poor guy initially had smoke from the passenger footwell, and that he disconnected the battery after that, so this is likely not a loose cable problem.

CKCars

Bill, the answer is Yes. The B+ post at floor board is 3.2V. The B+ under hood is 12V +. If I disconnect the wire at B+ under dash... than I have the 12V there. Only when it's connected to the post it is reduced to 3.2V.

I tried it with the lights on and both the under hood and cabin terminals are nearly the same reading.

I do have a list of CODES. I hooked back up the fuse box under the dash and here they are as follows:

REDUCED ENGINE POWER

10-PCM NO CODES

28-TCS C1255. H

40-BCM. NO COMM

58-SDM. U1000 HC
U1040 H
U1064 H

60-IPC. U1160 HC
U1176 HC
U1040 H

80. NO CODES

99-HVAC. NO COMM

AO-LDCM. U1064 H

A1-RDCM U1064 H

BO-RFA. U1096 H
U1000 H
U1016 H
C21000 H
C2110 H

AND ... SERVICE ENGINE SOON. lol

I hope this is helpful. Thk you

GCG

When it reads 3.2v in the passenger fuse box B+ stud, what does it read in the under hood fuse box B+ stud, and in the battery + post?


12.x volts or 3.2v?

CKCars

I have at the battery and B+ post under hood 12V

I just posted in the content for Bill.... all the error CODES. Can you see them?

REDUCED ENGINE POWER

10-PCM. NO CODES

40-BCM. NO COMM

That's just a few of them. If you need the list... let me know

1m

Bill Curlee

The B+ wire from the under hood FUSE BOX B+ terminal to the Passengers Foot well Fuse box B+ terminal seems to be defective.

If it were me,,,, I would temporarily disconnect it and connect a temporary wire between the two B+ terminals.

Our Major Powere wires have CRIMPED wire eyelets. Sometimes those eyelets come loose, get corroded or burnt and loose continuity,

I would at least inspect each crimp eyelet and make sure that the connection at the terminals are 100% good.

I have see damaged wire covering. The damaged sheif allows moisture/water to enter the cable/wire and the stranded copper wires turns green and disolves. Use an OHM Meter and read END TO END on that B+ wire. It should read ZERO OHMS!

Bill

GCG

It would be interesting to know the voltage at the 3 points with the blue connector off and then with the blue connector on.

But if your battery only have 12.0v it is discharged. A fully charged battery should have more than 12.6v and placing a load on it (like turning on the headlights) shouldn't bring it down to 12.0v

As I mentioned above, make sure your battery is fully charged and have it load-tested at an autoparts

CKCars

Bill, My question would be.... why is the B+ under hood to B+ under dash be the culprit... if when you disconnect it from the under dash positive fuse post... it than reads 12V

Only when it is connected does the voltage drop. Also do my error CODES show any direction?
Am I missing something here. Thk you.

Bill... UPDATE:

I checked the wire between B to B and it visually ok and testing is ok. I had it disconnect on both ends. I than put it back on the under dash fuse box post and my meter gets a real small reading under a fraction like there is feed back. I think it was like 0.14

I have read some other threads that when the dash message was .... REDUCED ENGINE POWER that several have said tge BCM was the problem and had shorted out from moisture and or corrosion. We think the smoke was on the passenger floor board. Can the BCM have cooked when we shorted the fuse box???

Another question would be does the blue wire harness connect with the BCM and when the short occured it shorted the BCM and now when connected pulls the voltage down on fuse box.

I guess I could unhook the BCM and see if the voltage at the fuse box keeps 12V+

My next test. Hummmm

CKCars

I do have a bit of a discharge from working on it. More like 12.3V

With the blue wire harness attached to under dash fuse box it is 3.2V. The battery and under hood fuse box read 12V+. If I disconnect the B+ post under dash.... the wire with eyelet test 12+V along with under hood and battery.

I hope this is helpful

GCG

12.3 is not good. You should fully charge your battery.

This seems to point to a bad link between the B+ stud from the under hood fuse box and the B+ stud in the passenger fuse box. Thoroughly clean both ends and securely tight it. As Bill mentioned, from B+ stud to B+ stud you should have 0 ohm (or very, very close to zero), otherwise a significant voltage drop might happen under load. With no load (open wire) you'll see no voltage drop. This is probably what's happening now.

CKCars

I just,disconnected the BCM and now I have full voltage at the fuse box post under dash. This would cause me to think the short is in the BCM. The blue harness,was still connected to the fuse,box...

​​​​​​As I noted... no issues were found with the hot between B+ to B+. I have read in several,places that the BCM has gotten wet and shorted and the error message on dash was REDUCED ENGINE POWER.

Am I in the right area or not???? Thk you

GCG

It would be good to know for sure that you don't have a bad contact at some point along the path from the battery + post to the B+ stud in the passenger fuse box. It's easy to determine with a multimeter. A voltage drop of 9.1v (12.3 - 3.2) is alarming...

Check the continuity between the + battery post and the B+ stud in the passenger fuse box. It should be 0 ohm (or very, very close to zero).

This simple test will let you continue the troubleshooting process with a better perspective

Regarding the state of charge of your battery, you could use this as a guide:

If the battery is

12.5 = 85% charged
12.4 = 65%
12.3 = 50%
12.2 = 35%
12.1 = drained

CKCars

The check on the wires from the battery to B+ under hood has past test. The wire from B+ to B+ under dash has also past test and was disconnected from both positive post when checking.

I think I must not be representing my issue very well. ONLY when it is fully connected ... the wires ... and all plugs into the fuse box under hood are in place does the VOLTAGE drop .... ONLY at the B+ Post Voltage reading then DROP TO 3.2 Volts or across any of the fuse.

If I disconnect the BLUE wireing harness from the FUSE BOX... and then Voltage return to 12+ Volts...
***OR***
DISCONNECT THE "BCM" PLUG-IN WIRES (3) AND THE VOLTAGE RETURNS TO 12+V.

This leads me to think... that the BCM has a short and that the Blue plug-in to the under dash FUSE BOX in part is how the BCM is connected. We KNOW that there are 4 fuses in this fuse box panel that are related to THE BCM... So it might be that if the BCM is faulty and failed can be shorting the fuse box under dash.

DON'T FORGET THE DASH ERROR MESSAGE AND CODES.

"REDUCED ENGINE POWER" AND 40-BCM NO COMM

I hope someone can confirm that the Blue fuse box wire harness is INDEED connected to the BCM. And if the BCM had shorted out or failed... could reduce the current at the fuse box under hood.

I guess it would be simple if someone new this answer and said No it is not or Yes it is and can short the Voltage to this location.

I will consider replacing the BCM and if when I plug in a new one in.... the VOLTAGE remains 12V+ at all check point's... than we will have the answer.

It may be worth a go....

CKCars

So... Where is the best place to get a used BCM for a good $PRICE???

My part number on the part is #09367609

QUESTION: Can I select from other part numbers that are NON-Matching and from other years???

Mine is a 99-C5

Thks In Advance My Friends!