100% AGREE! Make sure that they list ALL the DTCs and ALL the messages in the DIC.. You always need to describe if it cranks but wont run or it just wont crank!!

If there are a lot of old DTCs, have them clear the old DTCs and then read the DTCs again immediately after attempting to crank the engine (without turning the ignition off.)

 

Hi C5 Diag, good point. This is a no start no crank!!! I turn the key and the only thing that happens is what you see in the video. No codes at all through the DIC. Please advise. No codes DIC

Thank you,
Kyle

 

FIRST THINGS FIRST, get a new high end battery, C5's need more than 12 volts. I try to keep all my batteries up to 13 volts and never below 12.7. I have never had any luck with trickle chargers. once or twice a month I do a full charge up to at least 13 volts. Use to have this really good charger that would get me 13.3, darn thing wore out. worked for 6 years Make sure you get a smart charger, look at reviews, Amazon is a good source.

Then do what these guys say, brilliant folks on this thread! Saved my bacon a few times and saved me a lot of money! Thanks again guys!

 

Took a look at your video and it looks like you have a Serial Data Buss issue. All those messages , bells and no gage issues make that a possible culprit. Have your family try this: Open BOTH doors and shake the rubber accordion tube and see if that issue goes away. Then try to start it, You need to have who ever you are going to have do the testing for you call me!!!

You have my number. PM Sent

Bill

 

Yeah, looks like the classic data bus issue !!...water temp maxes out and fuel gauge goes to empty and probably power windows don’t work !!..Bill will walk you through it !!...what happens is one of the cars modules loses power or ground or you have corrosion issues and that power or ground will back feed to the serial data bus...now the modules can’t talk to one another and that is what you’ll see !!...I’ll see if I can find the video I did shorting out a modules data line (won’t hurt anything) and you’ll see all that craziness !!!

 

Just had my car detailed including the engine compartment. Now my 4 main tail lights don't work when pressing the brake pedal or the hazard button. Those lights DO come on using the turn signal. Which ground connection(s) should I try cleaning first? I know a back hazard switch is a possibility, but I'll try ground cleaning before ripping the car apart.
Thanks,
Randy

 

The brake lights main components are the Steering Column Multifunction switch and the Emergency Flasher switch. The Flasher is a PRIME culprit in this sort of issue. CYCLE it a BUNCH of times and see if that changes the symptoms.
Your detailer may have pushed it and its no longer happy. The contacts inside can and do get dirty . If you find out that it is the issue, I would change it as it only gets worse over time.

 

Thanks Bill. I've cycled the hazard button a few dozen times with no luck. I'll order the part in the AM.

 

Is the AC Delco part available anywhere or is Dorman # 924-609 the only replacement part available?

 

Help! PCM - NO COMM !

Mini backstory: 2003 ZO6 (I am original owner), engine died (dropped valve..sad day..good chance I shed a manly tear..), car sat for a few years (90% indoors) with no electrical power. I recently installed an LQ9 and sent PCM to ECS to get a good base tune. After installing the PCM and connecting the battery I was presented with the Christmas tree alerts (Reduced Engine Power, Service Vehicle Soon, Service Traction Control, Low Fuel) in addition to the fuel gauge being bottomed out and the temp gauge being maxed out, and the four outer brake lights do not light (3rd brake light is ok, running lights are ok, just those brake lights). Also, the first time I turned the switch ON I could hear the fuel pump running, but havent heard it since that one time. It has had moisture in it before, evident by fog on inside of windows, but never standing water in footwells, nor water leaks due to HVAC coil drainage.

Per Bill Curlee's info regarding grounds on the C5 I located and verified every single ground. None were corroded, but each one was opened, cleaned with a wire brush, checked for pin retention, given a dose of anti-oxidation goop for electrical connections and put back together.
I also pulled and visually inspected each and every fuse from both fuse boxes (engine bay & pass. footwell).
So far I've pulled the comb from the 4-wire STAR connector in the pass. footwell retried cranking; it would turn over but not start.
I disconnected the battery completely and removed the BCM (while wearing an anti-static strap), opened and carefully inspected it for signs of water ingress, but found none (though my eyes arent as good as they once were).

After reinstalling the BCM I pulled the comb from the other STAR connector and, using a good digital multimeter, checked the resistance on the Light Green wire and the Dark Green wire:
Lt Green - Grnd: 3.4M Ohms
Lt Green - Positive battery cable: 12.87M Ohms
Drk Green - Grnd: 3.38M Ohms
Drk Green - Positive battery cable: -infinite- (no change)

I then reconnected the battery and checked voltage on the same wires with the switch in both an ON and OFF state:
Lt Green - Switch ON: 55mV with massive fluctuation (most likely due to the square DC wave form)
Lt Green - Switch OFF: 24mV steady
Drk Green - Switch ON: 8V steady
Drk Green - Switch OFF: 12mV with some fluctuation

If I get a chance later today I will open the wheel well back up and check the dark green wire (#58 in the Blue PCM connector, if I read Bill Curlee's and C5 Diag's info correctly) for continuity to the STAR connector, as well as grounding, and shorting.

Is there anything, AnyThinG at all I can check on top of all this??

What am I missing??

 

Forgot to include the DTC codes
PCM
NO COMM

BCM
B0502 C
B0507 C
B2482 C
U1255 H

SDM
B0090 C
U1000 C
U1016 C

RFA
U1000 C

TCS
U1000 C
C1296 C

 

Looks like you’re having some serial data issues !!... It’s looks like the dark green wire (PCM) with 8 volts is the problem !!...If a module (PCM in your case) loses power or ground that power or ground can back feed onto the serial data line...power is back feeding onto your PCM data wire...with a DVOM you should only see the voltage fluctuate between .3-.4 volts on the dark green wire...DVOM’s refresh rate is toooo slow to see 7 volts...that is what I see on my 2001 key ON...with a scope you will see a 0-7 volt square wave...2 pics of my dark green PCM wire with my DVOM and scope..did you check G106 which is the PCM ground and located above the starter...the negative lead of battery attaches there ??...just looking is not good enough...I would also check the PCM grounds at your PCM...I like to load test my grounds with an old headlight bulb...if you have a 12 volt test light connect it to battery positive and with key ON check your 2003 PCM grounds...Best to check grounds with PCM harness attached and key ON...you will need to back probe these pins with your T pin and touch the tip of the test light to the T Pin...light should be BRIGHT if ground is good KEY ON !! !!...your grounds are :

pin 1- C1 connector (black/white wire)
pin 40- C1 connector (black/white wire)

pin 1- C2 connector (black/white wire)
pin 40-C2 connector (black/white wire)

To check power connect test light to battery NEGATIVE...check these pins KEY ON:

pin 19 C1 connector- pink wire...this wire will power up with key ON or cranking !!
pin 20 C1 connector- orange wire- this wire should be hot at all times !!

ALSO check PCM fuse 16 and PCM B 23 I believe !!...AND you can remove the 2 PCM connectors and make sure you have no bent pins and no corrosion...I’d spray DeOxit on PCM and harness connectors ...make sure PCM harness is firmly secured !!...clean BOTH of those “combs” with sandpaper or emery cloth and reinstall !!

 

YEP,, You have a serial data buss issue.. Clear ALL of those DTC and then see what you see in an ignition cycle before you turn off the ignition. That 8 VDC reading is way out of the ordinary. With that on the buss, it wont work! You only need the BCM and PCM serial data wires jumped together to get the engine to run.
You can try that. Disconnect BOTH shorting bars and Jump pins B (PCM) and M (BCM) together and see if it will crank and run.

If you truly have 8 VDC on the dark green (PCM Serial wire) the above will not work. You have to resolve that issue. Try to find out where the stray voltage is coming from.

 

Thanks so much for the fast reply!
I did get G106 (wire brushed the stud and all eye loops until shiney, added no-ox compound and reassembled).
I also pulled fuses 16 & 23 and tested for resistance; both were good with no resistance.

I'll be back home in an hour or less and will check the PCM pins as you suggested and report back.

Unfortunately I don't have a scope (wish I did..) but do have a 12V test light.

 

K, PCM connected, switch on.

With one side of the test light on battery positive, and touching to ground points via backside of the red and blue connectors (1/C1, 2/C1, 1/C2, 2/C2), no steady light. Light comes on for about 1/4 second, I hear what sounds like a relay click and light goes off. It never gets brighter than an orange glow before it clicks off.

Moved one side of the test light to ground. Testing pins 19/C1 and 20/C1 and bulb lights nice and bright with switch on.
Switch off, only 20/C1 light up.

I also disconnected the battery, removed the PCM, and tested resistance of the 4 PCM grounds to G106. All four read 1.1k ohms
What else can I check?​ ​​​Are my grounds bad?

 

Quote " All four read 1.1k ohms" Holy Moses. They should be ZERO Ohms or very close to it Something like 0.02 or so Yes, you have a ground issue if that in fact is the reading

BC

 

Will try to trace out each of the four grounds in a little bit and let you know whati find.

Could I, in theory and only as a last resort, run the four of those to the nearby frame rail and create a new ground point for them? Not ideal, I know, and I want things wired up the way they are supposed to be, but since all grounds are the same it could be something to keep in mind as last ditch effort

 

1.1 K ohms ???...I usually don’t test grounds using resistance but that’s way to high !!...with test light it should be nice and bright...did you try using the test light when you disconnected the PCM connectors ??..good job so far !!

 

There are 7 wires in a splice (S120) that all go down to G106...the 4 PCM grounds, the TAC Module ground, MAF ground and the ground for the control side of ignition relay 42...try this...remove the MAF sensor connector and check its ground with the test light connected to battery positive !!!...It’s either a back or black/white wire....BTW S120 is located 5.9 inches from the branch of wires that lead to the PCM...if the MAF ground is bad the high resistance may be between S120 where all those wires are joined and G106 !!...also you may have corrosion where the eye terminal is crimped to the wire that may not be seen...how did you arrive at those K ohm readings ??...did you check from the PCM harness to G106 with it removed or from PCM harness to ground with your other multimeter lead ???

 

I figured it would be an effective continuity test to ensure wire integrity.
I didn't think to try the test light when the PCM was out, but I did rerun the test and got the same results of 1.1k ohms.


​​​​​​​
I found S120 while tracing the grounds from the PCM. From S120 I see 3 black/white wires: one I traced back to the ignition relay in the engine bay fuse panel, but the other two disappear into the harness as it goes behind/beside the engine. I can only presume one these is going to the MAF, but not sure where the other is going. Coming from that direction (from beside the engine) are ground wires that go into the splice pack behind the battery. When checking resistance on these wires (one probe on the PCM grounds, the other checking each wire in the splice pack) to find the one that went to S106, I found one with little/no resistance, 2 with 1.1k ohms, and the rest were infinite. Now wondering if the ground issue is with a different module and the PCM was only a symptom.

Will check the MAF ground next, but still unable to definitively identify the PCM grounds wires after the disappear into the harness by the engine.

I got the original 1.1k ohms readings by removing PCM and testing across the PCM pins and G106, but only after the test light failed to light on these same points with the PCM installed.

I've checked with PCM in and out, and to G106 and to the eye loop on the end of the wires that attach to G106 while the eye loop is disconnected.