OK, here we go again... 2005 base model about 110,000 miles. Bought new battery at the end of November 2022, 3 year warranty.
I had an issue with it not cranking or starting on a few occasions in the past year of ownership, so aggravating.

It is not cranking or starting, nothing. all the lights work, dash, stereo, etc.

I replaced the starter relay already, checked every fuse, the grounds all seem good. Battery cables secured tightly, no corrosion.
Last time I had this issue, I brought the battery back to Walmart for testing (about a month after purchase), tested fine.

Before I put the battery on a charger, it read 12.5 V, I have had it on a charger for about 5-6 hours, reading 12.5 V. I do recall in the car, the gauge would read something like 14V on the dial, which it is not now.

I am so frustrated, thinking of just rid of this car.

Can anyone please help with advice? This is my daily driver, and luckily I work from home, but am stuck.

 

Sometimes these no crank/no starts can be a communication issue....you can try disconnecting the battery and with an ohm meter see if you see 60 ohms between terminals 6 and 14 of the DLC (where you hook a scan tool up to)...also you should see around 2.5 volts on each of these 2 terminals with a DVOM with battery reconnected.

 

ok, here are my results.

battery off the charger is 12.8v

battery connected, pin 6 above reads 1.36 v
pin 14 reads 1.36v . I did it again they both read 1.28v that time.

battery disconnected, between pins 6 and 14 is reading 95.3 ohms

what is this telling you?
and thank you very much!

 

So with the ohmeter leads connected to 6 and 14 you’re seeing 95.3 ??…and with voltmeter red lead to terminal 6 and black lead to ground (or using pins 4 or 5) and then 14 you are seeing 1.36 ??…I think you may be using voltmeter leads to 6 and 14 ??

 

I will watch the video shortly.
Yes, battery connected, pin 6 red lead Voltage on meter, black lead to a non painted bolt in the driver footwell for ground, I get 1.36 V, same for pin 14 red lead on meter, black to same bolt.
Battery unhooked, set to ohm on meter, red lead on either pin 6 or 14, with black lead on either pin 14 or 6 yeilds the readings above.

What is that saying?

 

If you are doing this testing correctly seeing 95.3 ohms is telling me you either have an open or high resistance in the CAN high or low wiring especially with the low voltage…the GM LAN operates on a 2.5 volt bias (I’d have the ignition in run mode”and it’s really best to use a scope on this because the signals wire operate in the microsecond or millionth of a second range…there are 2-120 ohm resistors in the BCM and ECM so them being in series you will see 60 ohms if wiring is good…first I would make sure your DVOM leads are good…they should read 0.0 or 0.1 ohms when held together…you always have to trust your equipment…the data bus wiring is below…second if you have a “better” scan tool to see what modules you may not be able to communicate with…CAN high and low wires are “twisted pairs” and are twisted together…terminal 6 is CAN high and 14 is low….CAN high wire is tan/black and low is tan…what I would do is disconnect the BCM connectors and with a jumper wire connected between the high and low terminals see what the resistance is now at 6 and 14…should be 0.00 or 0.01 ohms…this may just be corrosion on the connector…if resistance is good just reconnect the BCM and then go to the VCIM (Onstar) if you have it…from there ESC, TCM (auto trans), EBCM, and finally the ECM checking resistance jumping 6 and 14 at each module…I believe we had someone with a similar concern and his was the EBCM…any module outside the car would be suspect !!

 

Update: the multimeter leads touching each other together on Ohms reads 0, so that is good.
I hooked the battery negative terminal back up, took off the charger. The car started up, cranked about 5 cranks before started.
Dash voltage gauge now reads 14.3 V. Confirmed with my meter at the battery, 14.4 V
Tried it again, started up.. took about 5 cranks, which is a condition I have had in the past (aggravating)

I checked pins 6 and 14 again. With the ignition off (which is the only way I tested last time), pin 6 is 1.36V as well as pin 14. However, with the ignition in the Run mode (green circle on start button), pin 6 reads 2.45V and pin 14 reads 2.25 V.

Is that better?

The only thing I have recently changed on the car is added a front facing camera, which is hooked directly to the battery. I now realize that I should have tapped into a switched fuse or something under the hood, such as power windows, etc. I wonder if this camera is causing parasitic draw? I would think so, as tiny as it is. I just drove the car Saturday no issues for a few hours. Then come Monday night, no crank, no start.

 

Still 95.3 ohms across 6 and 14 ??…is that camera wiring connected anywhere else other than the battery ??..a scope is really helpful in this diagnosis other than just looking at voltage !!

 

78 ohms battery disconnected across pin 6 and 14.
camera is disconnected, but it just goes to the aftermarket stereo RCA type of jack, and power only, at the battery, 2 leads

 

Resistance is too high…you may have to start checking the CAN wiring or the module connectors…unfortunately we don’t have the silver bullet for you !!

 

Is it possible the clutch pedal sensor/ switch is failing intermittently? You could try disconnecting the wires from the sensor and connect them together. Be sure the car is in Neutral when trying to start.

 

Not to send you off in a different direction but have you seen this? I have a 2005 and have struggled with battery drain over the years. This became more severe after an ECM failure / repair. Battery would die within 3 days. This was applied and so far no issues. Good luck with the diagnosis / repair.

Mike

 

Is this something I would take the car to a dealer for? I do not have the tools to do this.
Thank you

 

Yes, or a trusted shop. I don't use the dealer.

 

or keep it simple and check for 12volts at starter solenoid when trying to start it. any noises/ click while touching the start button?? i mean under the hood, not inside the car. you said new battery, how are the battery cable connections at the battery?? totally clean and tight? i find a lot of times its something simple.

 

Had exactly the same issue, battery would just drain as well (radio, etc. worked fine), no crank, no start, swapped batteries, same issue, charged battery with a charger overnight, all fine and dandy, got out of work, battery at 6-8V, then charged on the way home to 12V+, overnight it drained to 6-8V again and would start as if I'd put a couple beers in the gas tank, a couple of days later, car died at a Costco after putting gas so some people helped me push it, so embarrassing, it would not start at all, called insurance, tried to jump-start but no dice, had to have it towed home.

Long story short, issue was the starter motor, here's a video I took of the problem:





Part number is (GM 3231625), I got mine at Rock Auto (remanufactured).

 

Well, I am back to no car to drive. I am ready to drive the car off a cliff at this point! This has been my dream car for 40 years, and I can not trust it even when it does run.

Anyhow, I am back to no crank at all, dash and multimeter read 12.5 V, push the starter button, nothing happens, except the dash lights go black and turn off, then back on, no interior clicks. Left the battery on the charger for 1.5 days, still 12.5 V and nothing.

What I found is that when the car is running, it shows 14.4 V, and if when I get in the car and push the button once, if the voltage shows more than 13 + V I have a feeling it will start. How can this be, I thought these are 12 V batteries?? All connectors tight, battery, ground, alternator.

@C5 Diag , I have not looked at the CAN connectors yet, I will try this on Saturday. I have no idea what left to do at this point. I am in Chattanooga, TN. I am guessing you are in Florida. Hell, if I got it started, I would be willing to drive it to you, and pay you to get this working!

ANY other ideas on what to check? I only have a regular multimeter, and can't really afford a $500 scan tool at this time unfortunately. Time are very tough financially at home

I

 

You could always take it to be diagnosed professionally, you don't have to let them repair it, just know exactly what's wrong with it, shouldn't be that expensive and you would now have a better starting point.

 

With the resistance reading higher than the normal 60 ohms you will have to check each CAN wire between all the modules..no need to come to Florida but you have to find the RIGHT shop to handle this…not a general repair shop or a dealership…a DIAGNOSTIC shop or auto electric shop can easily find the problem…not to much else I can help you with !!

 

Did you check the clutch pedal position sensor as suggested by shorting the 2 wires together?