lionelhutz

Dave, I'm starting to think you may have an internal issue in the foot well fuse panel. Power gets to the input stud but it doesn't properly get to the things it powers.

We'll wait for Sam to post what he tested.

David Shiel

If that fuse box is the case, I keep puzzling over the fact that the car started and ran perfectly before I unplugged the BCM, but this whole thing is way out of my wheel house. Your interest is really appreciated.
I keep thinking BCM or BCM /PCM communication. I never had any SES, service traction control or check tire monitor system before my BCM ectomy. No blown fuses in the fuse boxes.

Sam will be vacationing for a few days , but I am sure he will fill everyone in. At least so far we isolated the rapid battery dc problem and Autozone provided me a new 3 year/84 month battery free.
Thanks Again,
Dave

Bill Curlee

Humor me!! Find the Theft deterrent Relay.. Its above the BCM on the Fire Wall... It will have FOUR wires. RED, PURPLE, yellow and Yellow / black stripe.

Remove that relay. Locate the Purple and red wires in that relay socket.

MAKE SURE that the car is OUT OF GEAR!!!!!!!!!!! Chock the wheels!


Turn ON the ignition to RUN. Use a piece of wire or a paper clip and connect the RED and PURPLE wires in that socket.

That will or should IMMEDIATELY cause the starter to engage and crank the engine. See if you can crank the engine and see if it will RUN. If the key is in RUN and the engine cranks, it should catch and run.

If it cranks but does not run, see if you can read the DTCs BEFORE,,,,,,,,,,,,,, you turn the ignition switch to off.

Bill

David Shiel

I went out and took a look at it. There is what looks like a plug, and I saw a purple wire, but others are taped. Looks like a green plastic retainer clip on bottom. Does the relay face to front of the car forward of where the wires plug in? And, do you just pull the relay out toward front of car? Don't want to screw it up more.
Will it be diagnostic if car starts and thus drill or narrow down the root cause of the problem?
Will tackle in AM if I am on right track.
Thanks,
Dave
PS Sam spent about 5 hours on it and had his 4 volume service manual set with him. Taught me the basics of the schematics.

Bill Curlee

Dave

One day my Z wouldn't start. It was COLD and I was tired .. SO,,,,,,,,,,,,,, I ripped that damn relay off the fire wall and seperated the relay from the socket.

The relay is atached to the fire wall. The connector can be removed from the relay but its tough when the relay is in-place.

You can insert a jumper into the relay SOCKET from the rear as well and that also works.

Just remember........ Once you insert that jumper, the engine IS GOING TO CRANK, or at least it should.
If the key is in the RUN position, it should crank and run.

The relay is secured to the fire wall and the relay connections face REARWARD.


You have my number,,, Call me if you need to..

Good luck brother.

Bill

lionelhutz

Dave, I'm thinking when you were in the foot well messing with the BCM you bumped the fuse block or moved the wiring and it went to crap.

What does relay #46 do? It's a lot of schematics to go through searching for it.

lionelhutz

OK, relay 46 is the rear window defogger.

The fuse box should basically be divided into fuses that are hot all the time, hot when key is in acc and ign positions or hot when key is in the ign position. here are some important ones

fuse - when powered & what powered & color, connector pin, connector number


Fuse 25 - hot & BCM and IPC & Orn, F8, C1
Fuse 23 - hot & BCM & Orn, B7, C1
Fuse 9 - acc and ign & BCM & Yel, A3, C2
Fuse 13 - hot & BCM & Pnk, C4, C1

Hopefully, you know how to read the above. Basically, check the voltage at the fuse, check the fuse and then you'll have to get under the panel and check the wire coming out of the fuse block.

I would recommend you check the voltage at each wire while connected in circuit. Sometimes, without a load a wire with a bad connection will measure just fine but once loaded the voltage drops and it won't measure right.

Bill Curlee

Hmmmmmmm... I looked for relay #46 in 2001 FCM and did not find that specific relay.

If you look in the lid for the relay/fuse box cover,, what does it say relay #46 does for you????????

Is it in the under hood or passengers foot well fuse box?

lionelhutz

Bill - My service manual says relay #46 in foot well is RRDEFOG fed from fuse 48. I didn't see a relay #46 in the under hood box but I didn't look too hard for it there.

Bill Curlee

I have ESI schematics and it does not list 46. Dont know why..

Bill

David Shiel

front of me. It is a mini relay #46 on my cover and is for rrdefog. Never had issue with that. It looks on schematic like it is fed only from the BCM on CJ2 HVAC equipped models. It just kept rapidly cycling and drained battery. We (Sam and I) took it out and put 12 V to it and it seemed function properly. Reinserted it and it malfunctioned. Wrong message from BCM????

I took a break today as I am tired after the day with Sam and really frustrated with the damned thing. When I get this frustrated, I walk away for a little bit. But, I am going to go get some wire for a jumper for the red /purple jumper you suggested.

I have checked all fuses for continuity. All good. Not sure how to do the fuse socket volt test. When I took the BCM out the cover was on the fuse box and battery disconnected.

lionelhutz

I can't recall for sure. Are there little openings in the end of the fuse where you can probe to measure voltage?

David Shiel

and plug off it with the plug sockets nicely exposed. Tomorrow Vicki will be home, and she can sit behind the wheel when I jump the red/ purple wires with key in run. Feel safer that way.
I talked with my tuner and he pulled my file. He said he tuned security out of the PCM.
Battery is holding at 13 volts and I think I hear a very slight hum from the BCM. The mini relay #46 is out also.
I will call you after I do the jump of red/purple. I think Sam is eager to talk with you. I left you his number.
Thanks, Dave

David Shiel

for probes on top.

lionelhutz

Bill - Does the IPC work at all if you disconnect the star connectors so the IPC data link? Not sure if you know that one but just wondering. The gauges don't get their signals from the serial link but maybe the whole cluster is turned on and off by the serial link.

Dave - Well, then you know you to check at those probe test points. One side is the power side so that lets you know the fuse has power. The other side is the fuse output side and testing at that side lets you know the fuse is not blown. As for checking the wiring after the fuse, you'd need to go under the fuse block or to the connector of the item powered by the fuse.

I was thinking about this a bit more and it might help if you try everything and list what works and what doesn't work. Like lights, signals, radio, hatch release, gas door release, HVAC, etc etc.

David Shiel

Thanks Lionel,

1. I made a jumper from a copper coax cable to jump the red/purple wires to see if it will start. Try tomorrow and call Bill with results/ codes

2. I am becoming more convinced that the BCM is FUBAR.

3. Every wire and fuse we have checked has been fine. Prior to BCM removal evry thing worked OK except com codes and intermittent IPC out.

4. The RRDEFOG mini relay gets triggered, likely by the BCM, and runs the battery down rapidly. Our check of the schematic looked like on the CJ2 auto HVAC optioned car the only power feed to that relay is the BCM. It is out of car now.
.

5. Radio , PW, vert hatch and trunk are out .Interior lights ot also.

6. Seats, mirrors, memory , all driving lights, gas door, power telescope , hazard, turn and brake lights, horn and power locks work fine. Can't run HVAC as can't start car, but blower works. Slight flicker on temp dial **** areas which I did not have before

7.I can pull codes and check various system messages on DIC
IPC fires up then goes off.
So that is where we are. Again, will try the blue /red relay jump start tomorrow

Greg_E

I looked up the schematic for a 2001 Corvette in GM SI manuals and there are two schematics. C60 and CJ2. Not sure which one applies to your car, but both of them show Relay 44 as being RR defog.
Edit:I looked up the schematic for a 2002 and it does have relay 46, RR defog. You must have a late model year 2001 and the change was implemented prior to the 2002 model.

I don't want to get you off track, but just as an FYI, this is how that circuit is supposed to work.
The coil of the relay receives ignition voltage thru HVAC fuse 18 (10A) when the key is on. When the BCM receives the RR Defog on request from the secondary rear defog switch on the HVAC module, it grounds the control circuit in the BCM, energizing the R46 relay.

lionelhutz

4. The RRDEFOG mini relay gets triggered, likely by the BCM, and runs the battery down rapidly. Our check of the schematic looked like on the CJ2 auto HVAC optioned car the only power feed to that relay is the BCM. It is out of car now.

Yes, the BCM triggers that relay.

5. Radio , PW, vert hatch and trunk are out .Interior lights ot also.


- I believe the BCM tells the radio to power up.
- I know the hatch and trunk run through the BCM.
- I don't think it has anything to do with the PW. I believe the left door module just sends a signal to the right door module.
- Interior lights = courtesy lights? = BCM controlled


6. Seats, mirrors, memory , all driving lights, gas door, power telescope , hazard, turn and brake lights, horn and power locks work fine. Can't run HVAC as can't start car, but blower works. Slight flicker on temp dial **** areas which I did not have before

- Fog lights? = BCM controlled
- DRL? = BCM controlled
- Key chain fob? = BCM controlled
- I don't believe the BCM controls the gas door. I didn't see it in the BCM schematics but could have missed it.


7.I can pull codes and check various system messages on DIC
IPC fires up then goes off.



So when you say IPC is out what do you mean exactly? I thought you were meaning everything - gauges and DIC.

Does the DIC give any warnings, like a door or hatch ajar warning?

What was the state of the car when you did the above? BCM installed and star connectors in place?

I'm reading some stuff here that is BCM controlled. It may not be working right, but it doesn't appear to be dead either.

David Shiel

Car started by removing relay and jumpering red/purple. Getting reduced power warning , but car runs like a bear. I tried BCM relearn just in case before jumper, but no diff from that.

Windows and radio began working while car was running.

Cooling fans are out. Hatch and vert tonneau still don't work. IPC in and out. I still have mini relay 46 and security relay out( so I can upper the car.

Bill took a lot of time on the phone and was very patient with this electronic klutz. Thanks Bill. He is thinking foot well fuse box, possibly ignition plug. I'll see if I can get fuse box out a bit later today.
A friend who used to do all Hendrick's electrical work, just called to chat. I told him what was going on and he agreed with Bill, but added his money is on a BCM problem. I think a check of the fuse box and ignition connector will further hone us in.
Thanks again Bill and all, Dave

David Shiel

the car state was stars and BCM connected.

Windows and radio are again out with engine off. Can't pull codes now. No warning lights about hatch or door ajar. Yes, when IPC is out that includes HUD and DIC

I am going to try to check wiring under the fuse box and get to the ignition plug and jiggle it some if I can, as Bill suggested. We got some funky voltages on the fuse box.

Based upon what you last sent on the many things controlled by the BCM, I keep going there.

My friend said he has seen all of this on the C5s, decries the cheap plugs and says, as you folks do, that it takes very little in terms of low volts and bad plugs to really screw them up. He said he has had to replace a lot of BCMs, and fewer PCMs
Oh yeah, interior and courtesy lights are out. The gauge lights and door switch lights work.


Thanks for hanging in there. This should become a real learning experience.