[zee750s]

ok im tearing my hair out. i have replaced the bcm pcm and the starter switch. i also cleaned all the grounds on the interior. and tore apart the old switch and cleaned that and cleaned the lock cylinder as well. but i still have no gauges it came on once when i bought it now not at all. the check engine light is on but no mileage speed gas or temp working. please help i cant afford to spend to much on this car and love doing things myself.

 

[Starship]

The instrument cluster on your Malibu gets the speedometer, tachometer, and CEL from the PCM on separate circuits and the rest from the BCM over the serial data interface. I hope you didn't just throw the PCM and BCM together without reprogramming.

 

[zee750s]

i just plugged in the new ones and it didnt turn on the gauges so i put the old back in. nothing about reprogamming tho. do i just disconnect battery and relearn key to do this if so i did.

 

[Starship]

You need to take it to a shop that has a scan tool to do the programming. I'm not quite sure what's been done and why and thus there isn't much I can suggest.

 

[zee750s]

everything is back to the original parts. just tried the others in hopes that it would work. but didn't so I put out back the way it was.except for the ignition switch.can any scan toollike the one at autozone reprogram this. do I even need to since its all back to original parts? where are the ground locations at by the way . might have missed some.

 

[Starship]

If you put the original PCM and BCM back, there's no need to program. And, the kind of scan tools you need are professional ones costing thousands. See the instrument cluster diagram at http://cid-54465800aad91b49.office.live.com/self.aspx/pub/va103205.pdf. Maybe you can follow the wires to the ground splice points.

 

[zee750s]

If you put the original PCM and BCM back, there's no need to program. And, the kind of scan tools you need are professional ones costing thousands. See the instrument cluster diagram at http://cid-54465800aad91b49.office.live.com/self.aspx/pub/va103205.pdf. Maybe you can follow the wires to the ground splice points.

well thanks but i checked all grounds cleaned them up,and still no gauges.

 

[Starship]

When you turn the key ON, does everything initially look okay (lamps self-test, gauges sweep, etc.)?

 

[zee750s]

nope it just has the check engine light and the seat belt light on.

 

[DrivenDaily]

Starship, does his car have a 5V (or other voltage) regulator for the dash? All of my older cars did. It was a supply for the gauges only, not the lights. Do his gauges get the positive voltage, then go through the gauges, then to a modulated ground? Or does the ground come straight in, thru the gauges, then to modulated positive?

Knowing this could help eliminate sources of concern.

 

[Starship]

Oops, I had to go work on my heart rate. The dash gets the battery voltage. The serial data interface uses UARTs and thus the circuitry is getting 5V. After that, I'm not sure how sophiscated things get. Now, you are asking what I've never paid attention to.

The "seat belt light" tells me that it is getting something from the BCM. Now a lot of the gauge data first go to the BCM and then onto the instrument cluster. I'm surprised that the CEL hasn't been scanned for. How about it, zee750s?

P.S. I had to read what you said twice, DD. I think the latter is the case. You can't have a floating ground with the serial data interface.

 

[DrivenDaily]

So, if the gauges all run off the 5V supply, get their display signals from the BCM, and have a solid ground, then I might suspect the BCM. It seems to be one of the sources that could fail and take out various devices in the process. There's also the 5V supply that needs to be verified.

Of course, with low voltages dirty contacts can play a lot of havoc. I just learned that lesson with my DSLR camera. Intermittently it would not auto-focus. A guy in the camera club suggested that I clean the contacts between the lens and body. I did and the issue seems to be resolved! Point being, maybe the OP could take any contacts and carefully clean them to see if that helps.

Logically, all we're trying to focus in on is what device or connector could cause this all at once, then direct him that way.

PS - Glad you had your heart rate monitor nearby!

 

[Starship]

Since the BCM was swapped once, I'd think that ruled out dirty contacts at the connectors. There probably are DTCs both at the PCM and BCM that may shed light. It may just be a bad instrument cluster. It'd be so easy if everyone had a cool scan tool at their disposal.

Heh, my resting heart rate has been steadily coming down but I'm not there yet (goal is low 50s).

 

[zee750s]

Since the BCM was swapped once, I'd think that ruled out dirty contacts at the connectors. There probably are DTCs both at the PCM and BCM that may shed light. It may just be a bad instrument cluster. It'd be so easy if everyone had a cool scan tool at their disposal.

Heh, my resting heart rate has been steadily coming down but I'm not there yet (goal is low 50s).

ok 3 things .
1i replaced the speedo still nothing
2 what dtc? are and located
3 I hope you get better thanks for the help so far

 

[Starship]

I've started saying "DTC" as in Diagnostic Trouble Code because simple "code" to me often means an expression in a programming language that gets compiled into the firmware. I guess I could've said "to hook up an OBD scanner or code reader." And, I'm not currently sick or anything but have been working on my cardiovascular conditioning. Thanks for your concern, though.

I suggest getting it scanned for the diagnostic code(s). One thing that occurred to me is whether the instrument cluster ("speedo" if you will) is getting the constant power it needs. If you feel up to it, with the key OFF, pull the IPC/HVAC BATT fuse from the left instrument panel fuse block and then make sure the fuse isn't blown. While you are at it, measure the voltage at the junction with a multimeter. There should be 12V or better present on one side of the junction that should be hot at all times.

Do the same for the BCM with the BFC BATT fuse in the left instrument panel fuse block.

The other fuses labeled either BFC something or Body Function Computer only come into play with the key ON or ACC. Locate them in your owner's manual and then make sure they aren't blown.

 

[zee750s]

I checked the fuse first thing, none were blown.but ill check the power issue. should the bcf be constant as well?

 

[Starship]

Yes, these things are basically computers and thus take some time to go through the power-on self-test. Thus they are supposed to be powered up always. They just go to a sleep mode when the key is OFF.

 

[zee750s]

ok inside the vehicle i got a 12.6 at fuse g and a .3 at fuse h with vehicle off. havent got to the underhood junction yet to dark now. had to finish van matinence, but does the one in the left panel get power from different places. im beginning to think its a broken wire somewhere. as i checked all fuses first and the were good. getting very frustrated. g i think is bcm and h is pcm.

 

[zee750s]

oh and the check engine light im waiting on because i want to get it to my mechanic friend first for that after i get gauges to work, i know sounds dumb but. i replaced the brake line and have to do tie rod ends on it next. i just want the gauges to work first before i go anu further.

 

[Starship]

The BFC BATT fuse is indeed fuse G but the IPC/HVAC BATT fuse is in the lower right corner. Fuse H is PCM ACC which isn't always on and thus you're good still.