have a 98 vette convertible...
trying to troubleshoot electrical issue with car...think might be a bcm issue anyone else have a issuse with bcm and what did car do ?

 

Why do you think you have a BCM issue??

Normaly when you do you have all sorts of DCTs. The BCM is VERY sensitive. It hates moisture and the slighest noise on the serial data line send it in to a NO COMMS ISSUE.

What DTCs do you see. If your not reading the DTCs using the DIC,, you may not be seeing them all...

READING YOUR Engine Diagnostic Trouble Codes (DTC)

This procedure should be carried out any time you experience a problem with your C5. Most inexpensive store bought aftermarket code readers will ONLY read power train DTC’s. Reading the DTC’s with the C5 built in code reader will allow you to read ALL the modules in the vehicle.

The Diagnostic Display Mode is entered with the following procedure:
1) Turn on the ignition but don't start the engine.
2) Press the RESET button to turn off any warning messages. (i.e. door open, trunk open ect)
3) Press and hold the OPTIONS button
4) While holding OPTIONS, press FUEL button four times within a 10 -second period.

Initially, the on-board diagnostics go into an Automatic Mode which will cycle through each module and shows diagnostic codes in a pre-set sequence: PCM - TCS - RTD - BCM - IPC - RADIO - HVAC - LDCM - RDCM - SCM - RFA. All codes will be displayed for each module. ( i.e. PCM = 4 codes) If none are present in a given module, you will see No More Codes on the display.

There are two types of diagnostic codes, Current and History designated with a letter suffix, “C” or “H”. A current code indicates a malfunction is present in the module displaying data. A history code indicates a problem existed sometime in the last 40 or 50 ignition cycles. When not accompanied by a current code of the same number, it's potential evidence of a previous problem, now resolved, that was not removed by clearing the codes. More likely it's an indication of an intermittent malfunction.

Intermittent codes are the most challenging of the diagnostics. An intermittent code may have happened once, may have happened more than once but is inconsistent or may be happening on a regular basis but not at the time the codes are displayed. History codes can also be caused by a current malfunction in a system that is not operating at the time codes are displayed. An example is the rear window defogger which doesn't operate until the Body Control Module detects engine rpm. For history codes set by a module that does not operate with the key on and engine off, a special diagnostic tool called a Scan Tester is necessary to properly diagnose the malfunction.

Once the system has displayed all modules, it goes into the manual mode which allows selection of each module using combinations of Driver Information Center buttons. Manual mode can also be entered during the automatic sequence by pressing any button except E/M. Once the display shows Manual Diagnostics, select a module by pressing the OPTIONS button to go forward or the TRIP button to go back. Once a module is selected, a code is displayed, and if more than one are present; press GAGES to go forward or FUEL to go back.
To exit the diagnostic mode at any time, press E/M. If you want to erase codes in a given module, press RESET To reset the codes once in manual mode, press and hold RESET until it displays NO CODES Press OPTIONS to go to the next module. Repeat the steps until you have reset the codes in all the computer modules.
NOTE!! Only reset the codes IF you want to - it is NOT necessary to do this. Clearing a code does not repair a problem. You are simply erasing the evidence of it in the module's memory. If you clear the code/s, and extinguish the Check Engine Light, your emissions status ready will NOT allow you to pass an emissions test until you have completed the required driving cycles. There are a few body module DTC’s that if set will prevent the module from operating properly. Once the DTC is cleared, the module will return to full function. This is not true for power train DTCs.

If you have never read and cleared your codes, there will probably be a lot of old history DTCs. It is recommended that you clear your codes and see if any come back during a driving cycle. Those are the ones that you need to concentrate on diagnosing.

Once you have the codes, the next question is: What to do with the information?
First, consult the factory service manual. Any serious C5 Do-It-Yourself owner should invest in the Corvette Service Manual of the appropriate model year. The Service Manual is really a requirement if you want to understand and work on your C5.

NOTE and a WARNING. You can read the DTCs while the engine is running. I pull mine up all the time while driving.
WARNING. Don’t become distracted while reading DTCs while your driving and cause an accident!!!!! Use common sense and drive safe.

These are some very good C5 Diagnostic Trouble Code (DTC) explanation web sites!!! They also explain how to read the DTCs

Here are some very good sites that explain what DTC mean:

http://www.gearchatter.com/viewtopic11755.php

http://www.obd-codes.com/trouble_cod...d-ii-codes.php

Make sure to include the H or C suffix when you post your DTCs!!


BC

 

Could you be any more vague?

 

no codes coming up, have a modis i checked that first...the car will start only if i disconnect and reconnect the battery, if i leave it sit it wont restart, dash does come on but the stero & interior lights wont come on, alarm is acting up, fuel pump is working. then i disconect and reconnect the battery then car will restart...also checked the battery it tests fine as does the grounds

 

YES,,, That is caused by your BCM. Its not coming out of sleep mode. There have been others with this issue. One forum member installed a switch in line with the BCM fuse so he could just flick the switch and not have to disconnect the battery. He also stated that one day he removed the switch and it worked fine!

You could remove the BCM, remove the circuit board from the box and clean the board. They get corroded and have all kinds of issues. The one in my 98 was horrible!

Give the board a look see and cleaning and see if that resolves anything.

BC

 

thank you i will check it out

 

found a great link that helped me pinpoint that the bcm is my issue...Troubleshooting C5 No start Issues
Let’s start troubleshooting why you car won’t start or has intermittent starting issues. If you turn the Key to the start position and hear a few clicks from the passenger footwell but the STARTER does not engage this guide may assist you. We start with the easiest checks and proceed to the pain in the *** checks.

1. First of all you want to check the DIC for codes that may help you track down the issue

The Diagnostic Display Mode is entered with the following procedure:
1) Turn on the ignition but don't start the engine.
2) Press the RESET button to turn off any warning messages
3) Press and hold OPTIONS
4) While holding OPTIONS, press FUEL four times within a 10-second period.


Initially, on-board diagnostics go into an Automatic Mode which shows diagnostic codes in a pre-set sequence: PCM - TCS - RTD - BCM - IPC - RADIO - HVAC - LDCM - RDCM - SCM - RFA. All codes will be displayed for each
If none are present in a given module, you will see No More Codes on the display.
There are two kinds of diagnostic codes, Current and History designated with a letter suffix, C or ;H. A current code indicates a malfunction is present in the module displaying data. A history code indicates a problem existed sometime in the last 40 or 50 ignition cycles. When not accompanied by a current code of the same number, it's potential evidence of a previous problem, now resolved, that was not removed by clearing the codes.
More likely it's an indication of an intermittent malfunction.
Intermittent codes are the most challenging of the diagnostics. An intermittent code may have happened once, may have happened more than once but is inconsistent or may be happening on a regular basis but not at the time the codes are displayed. History codes can also be caused by a current malfunction in a system that is not operating at the time codes are displayed. An example is the rear window defogger which doesn't operate until the Body Control Module detects engine rpm. For history codes set by a module that does not operate with the key on and engine off, a special diagnostic tool called a Scan Tester is necessary to properly diagnose the malfunction.
Once the system has displayed all modules, it goes into the manual mode which allows selection of each module using combinations of Driver Information Center buttons. Manual mode can also be entered during the automatic sequence by pressing any button except E/M. Once the display shows Manual Diagnostics, select a module by pressing the OPTIONS button to go forward or the TRIP button to go back. Once a module is selected, a code is displayed, and if more than one are present;
press GAGES to go forward or FUEL to go back.
To exit the diagnostic mode at any time, press E/M. If you want to erase codes in a given module, press RESET
To reset the codes once in manual mode, press and hold RESET until it displays NO CODES Press OPTIONS to go to the next module. Repeat the steps until you have reset the codes in all the computer modules.
NOTE!! Only reset the codes IF you want to - it is NOT necessary to do this. Clearing a code does not repair a problem. You are simply erasing the evidence of it in the module's memory.
Once you have the codes, the next question is: What to do with the information?
First, consult the factory service manual. Any serious C5 Do-It-Yourself owner should invest in the Corvette Service Manual of the appropriate model year. The Service Manual is really a requirement if you want to understand and work on your C5. They are available through Chevrolet dealers and mail order sources, such as Ecklers and Mid America.

The diagnostics for some diagnostic codes call for a scan tester. Also known as scan tools or scanners these units are really hand-held diagnostic computers. A little larger than a portable cassette recorder, powered by the car battery and connected to the diagnostic link connector (DLC); they collect computer module data and display it on a small screen. Scan testers are operated by a small keypad. Software is usually in plug-in cartridges covering a specific model year.
Where you might get stuck needing one of these pieces of equipment is when the Service Manual calls for operating a specific module with a scan tester. If you are trying to solve a diagnostic code and determine that a scan tester is required but don't have access to one; take the car to a service facility for repairs.



The following is a list of all valid DTCs for Corvette C5: The ones shown in RED can be the cause of a NO START situation. However there are others that might also cause this. Those listed are simply the MOST COMMON issues.


DTC B0605 BCM Internal Memory Malfunction
DTC B0851 Battery 1 Out of Range
DTC B0856 Ba
DTC B2252 Key Cylinder Switch Circuit
DTC B2253 Key Cylinder Switch Circuit
DTC B2282 Battery #1 Circuit
DTC B2283 Battery #1 Circuit
DTC B2284 Battery #2 Circuit
DTC B2285 Battery #2 Circuit
DTC B2721 PASS-Key Detection Circuit
DTC B2722 PASS-Key Detection Circuit
DTC B2723 PASS-Key Detection Circuit
DTC B2735 PASS-Key Programming Mode Active
DTC P0230 Fuel Pump Relay Control Circuit
DTC P0562 System Voltage Low
DTC P0563 System Voltage High
DTC P1626 Theft Deterrent Fuel Enable Signal Lost
DTC P1630 Theft Deterrent Learn Mode Active
DTC P1631 Theft Deterrent Start Enable Signal Not Correct



If any of the DTC Codes shown in RED are set, you can find information and troubleshooting atGearchatter.com



2. Check for loose (proper torque is 71 inch lbs) or corroded connectors on the Battery and Load Test the Battery ! Most Auto Parts Stores will perform a LOAD TEST for little or no charge. Do not Assume that because the connectors look clean they are. Better to use a wire brush and baking soda here to clean the terminals.

3. Try to reset the VATS system using the following procedure:

The typical 1998+ Passkey relearn procedure is this:
1. Disable your headlamps. Attempt to start the vehicle. Vehicle may or may not 'fire' and quit. Some vehicles will not engage the starter. This is normal. DO NOT TURN OFF KEY YET !!

2. Leave the key in the "on" position, until the 'security' light goes out or quits alternately flashing between "Security" and "Battery". This relearn period always takes 10 minutes. How long does this take ? 10 minutes. How long do I have to wait ? 10 minutes.

3. After security light is no longer displayed, shut the key off ! Wait 5-10 seconds and repeat the above procedure (steps 1 through 3) another two completed times for a total of 3 start-relearn-attempts, remembering to shut the key off between each 10 minute relearn procedure. This will take 30 minutes--no less. If the 4th start attempt fails to start the vehicle you did one relearn step (or all of them incorrectly). If you left your headlamps on until the battery went dead and voltage dropped below 10.5 volts, no amount of relearn attempts will be learned !!
Don't read too much into this. Most people cannot seem to grasp the simplicity of this relearn procedure.



4. Check the VATS pellet in the key. Try using your spare key to resolve the issue. If the car starts using the spare key then you want to try cleaning the pellet on the key causing the issue. You can do this by simply using Isopropyl Alcohol on a damp cloth, followed by sliding the resistor back and forth between a piece of folded paper.

If the car continues to start using the spare key but does not start using the original key after cleaning you need to buy a new key !

Determine your VATS code ( A GM dealer should do this for no charge) or

If you have a digital volt meter, set it on ohms mode and measure the resistance of the pellet on your key. The BCM is programmed for a specific resistance value. The BCM measures the voltage drop across the key pellet. If it is within +/-10%, then the car will start.
The 15 resistor codes are:
Key# Value (Ohms)
1 392
2 523
3 681
4 887
5 1130
6 1470
7 1870
8 2370
9 3010
10 3740
11 4750
12 6040
13 7500
14 9530
15 11800

If you're getting 1460, you probably have a VATS code 6. You can set where the decimal point goes, but the point is the number is within +/- 10% of the value for #6.



Once you have this number...

Follow this link to buy a double sided GM VATS key.
One good source for the blank key is http://stores.ebay.com/Locksmith-Source The number key you want is your VATS code #

Once the key arrives Take it to a local locksmith. he should charge you $2.00 to cut it

5. Bad ignition switch. Try to wiggle and pull on the key while holding it in the crank position, also try just holding the switch in the crank position for an extended period of time and see if it will start.
Instructions and photo's on accessing the Ignition switch assembly can be found HERE


6. Check Minifuse 14 (10 amp) and Maxifuse 52 (60 amp) in the passenger toeboard fuse panel Located on the passenger side under the carpet, remove floor cover then fuse housing cover.




7. Check the Theft Deterrent Relay TDR relay which is GM part number# 12177233 (Superseded by Gm part Number 12177235 which is a direct replacement) located above the BCM in the same location. The easiest method to check this is to remove the relay and jump between the purple and red wires on the connector, If the car starts with a jumper in place you need a new relay ! Do not operate the car with the jumper in place, This is for troubleshooting ONLY. Attempting to drive the vehicle with any troubleshooting fix could result in permanent damage or FIRE !

This relay is located right above the BCM in the pass. side footwell. It has 4 wires attached to it:

Coil side:
Yellow - +12v from ignition switch during starting.
Yellow/black stripe - Ground signal supplied by BCM.


Note this will only show continuity to ground during starting (assuming no theft protection is occurring...the BCM has the ability to prevent starting by not supplying this ground signal).


Load side:
Red - +12v from battery
Purple - +12v to starter solenoid during starting.




8. Bad Clutch Safety Switch Just disconnect the clutch safety switch connector from the switch, use a small piece if wire and jumper the TWO connections in the plug. If the switch is bad, the jumper wire will allow the car to start! ***Remember*** if you jumper that switch out, the car will start IN GEAR with the clutch OUT!


9. Loose starter connections. VERY COMMON ISSUE!!! Loose wires on the starter and solenoid will cause this issue! If there loose, it will eventually cause the wire and solenoid to burn up! (get crispy) Then it will FAIL! Put the car on jack stands or a lift and check all the wires on the starter solenoid. Located on the Passenger Side Engine Compartment.


10. Starter solenoid. If the TDR isn't bad, then the solenoid is probably bad If it fails to start and trying the ignition switch a few times doesn't work and you’re stuck, whack the starter with a hammer or a wrench. Quick check to rule out the starter and solenoid is to jump the terminals on the solenoid with a screw driver or remote starter button, (preferred method).
If the starter engages it's not the starter or solenoid.




11. Starter. If the brushes inside the starter are worn or the commentator ring is corroded or burnt, the same mechanical agitation described in # 10 will also alleviate that issue (temporarily)

12. Check the Block Ground located directly above the starter Make sure you have two wires attached to that ground ,it is clean , corrosion free and tight.

13. When the car no-starts, try this.

1) Turn key off and remove from ignition lock.

2) Pull fuse #25 (in the passenger footwell fuse/relay box), wait 5 secs, and re-insert fuse.

3) Try to start the car : IF it now starts OK, you have a BCM problem : it does not send the PCM the "Fuel-Enable" signal.



When everything works properly : the BCM is the "Power Master" of all the computer boxes hanging on the serial data bus. When you shut the car off, then remove the key, and then open the door, this starts a power-down timer in the BCM. This timer is about 20 or 30 minutes. If the BCM sees no activity (key put in ignition, a door open...) during this 20 minute period, it sends a "Power Sleep" mode signal to all the other modules on the bus, and they go into a low-power sleep mode (so the battery doesnt get drained).

The BCM goes into a sleep-mode too, but it still has enough functionality to recognize that a door has been opened, or a key was inserted into the ignition switch, which terminates this power-down timer and wakes-up all the modules.

This sleep functionality of the BCM is also there for the anti-theft horn alarm. In sleep-mode, the BCM can also recognize a hatch-release request from the RF remote control (key fob), and then the BCM activates the hatch release relay. (The hatch release signal comes from the remote radio receiver and is transmitted to the BCM on the serial data bus.)

If you have this no-start problem, the issue may be that the BCM does not come out of its sleep mode : it does not respond properly to the door-open switch inputs (or the key-in switch input, or the hatch release request). If you try to start your car before this timer runs-out (as evidenced that the interior lights come-on when you open the door), the car will start. If this timer expires, and all the modules (including the BCM) go into sleep-mode, your car won't start.

The problem is internal to the BCM : It does not come out of its sleep-mode when you open the door, or stick the key in the ignition (the "key-in/out" switch). If you pull passenger footwell fuse #25 (the one shared by the Instrument cluster and the BCM), and then reinsert it, this forces a power-on-reset of the BCM logic, which forces it to come-up in the waked-up state, and now the car will start.

Fuse #25 is the power feed to the BCM logic/CPU circuit.

before the BCM is replaced in order to still drive the car, Youcan rig-up a normally closed pushbutton switch in-series with fuse # 25 allowing you to reset the BCM before you start the car. You have 3 options to fix this :

1) Kludge-fix it with a pushbutton switch Take a mini-fuse, cut apart the plastic and save the metal pins (cut the fuse element that is between the pins. Then solder on a length of insulated wire, from one pin to an automotive blade-type fuse-holder. The other side of the fuseholder pigtail to some more wire, to the Normally Closed (NC) contact of a momentary bushbutton switch. Connect the other terminal of the switch (C) to another length of insulated wire, the other end is soldered to the 2nd fuse pin. Install shrink tubing to insulate all the connections. Install a blade fuse (same Ampere rating as fuse #25) into the added fuse holder, then plug the mini-fuse pins into the fuse-box, where fuse #25 was. To start your car, push and release the bushbutton, then rotate the key and start.

2) Replace the BCM with a new one (get the correct pn, there are 2 or 3 BCM part numbers used, depending on the model-year), but you must get the replacement BCM programmed by a GM dealer for your cars RPO options. Because the car won't run without this programming, you will have to have a GM dealer do the BCM replacement and reprogramming.

3) Find a used BCM, of the correct part number on the forum or EBay (or wherever), which has the same options as your car does, and therefore already has the correct RPO programming.

Note : The antitheft horn alarm will not be functional if your BCM has this wake-up problem, nor can you pop the hatch from the keyfob or the dash switch unless you hit the pushbutton first.


Below is the wiring diagram for the starting circuit in the C5:

 

Has anyone ever fixed the problem by replacing the BCM? EVER???
The cost for a BCM is too high to "easter egg" a solution.
I have checked everything mentioned and nothing is bad. Tech2 won't communicate until BCM wakes up. I plan to check all of the power and grounds at the BCM tomorrow. I just have not seen a post that replacing the BCM was a fix!

 

A fix to what?? Be specific.

 

I believe this whole thread is about the BCM not waking up!

 

Ok. I guess one size fits all then.

 

Well after scoping all power, grounds, and star connectors on this 2001, I ordered a new (rebuilt) BCM.
After the option programming and theft programming process, everything worked ok. The BCM wakes up after 20 minutes, 2 hours, and even overnight. I found a source for rebuilt "Cardone" BCM's at O'Reilly's for $139 and a core of $40.

They had to order in which cost $7.50 shipping, but did the trick.
There, someone has actually fixed the wake-up problem by replacing the BCM.

One for the books!
Steve

 

Hello Bill , Question . Does this apply to C6s also ? ,

 

if not whats the procedure on a 2006 vert , manual trans , Thx , Eric

 

Well,,,,,,,,,,,,,,,,,,,,,,,,,,, YES! The C6 BCM is even MORE COMPLICATED than the C5 BCM. It communicates on a serial data buss & a CAN Buss.

If you have C6 BCM issues, you might as well head straight to the STEALERSHIP.

When you get a new one, there's a LOT of programming that you need to do to get it to function properly

The BCM is part of the fuse box in the passengers foot well..

BC

 

Hmm... another accidental C6 post by a new user in the C5 section on a 4-5 yr old thread. I think its becoming a fad...

 

i looked on o'rielly's and could not find it. could you please provide a link or part number? thanks so much.

 

It's there check this:

http://www.oreillyauto.com/site/c/de...1596&ppt=C0335

 

My '98 had a whole slew of electrical issues, from security issues - wait 10 seconds, pull key, through dash lights going on and off for no reason when driving at night, etc., etc. Too many "gremlins" to recall after all these years.

It was under warranty at the time (around 1999) and after the dealer tried three of four times to fix it, they finally put a new BCM in, and all the problems went away immediately.

Now was it a faulty BCM or just bad connections or a bad ground? Who knows. But swapping the BCM fixed it - never had a problem like it since.

 

Hi im having the same problem
how can you help me or give me some info I can use
everytime I turn off the off and I leave and come back the car wont start. I need to take the battery off and connect again to start

this issue is giving me to much stress