2007 2.2 Ecotec Will Not Start - Chevy Cobalt Forum / Cobalt Reviews / Cobalt SS / Cobalt Parts
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post #1 of 18 (permalink) Old 03-28-2018, 03:17 PM Thread Starter
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2007 2.2 Ecotec Will Not Start

Hello all,

I was hoping to get some advice as to what might be preventing my 07 from starting. It's actually a 2007 Pontiac G5, but I did not see a place to post this on the G5 section. The car has had this issue intermittently for some odd time and usually starts working after trying to turn the ignition a few times, but now the car has not started for about a month. I don't hear the starter trying to engage, or anything. In the past I would sometimes hear faint clicks from the starter trying to engage, and it would eventually start, but not for the past month.

For the crank circuit I checked and verified that I'm getting a constant 12V on the big terminal on the starter. I checked to see if I was getting the 12V signal to engage the solenoid on the starter when trying to start, but I was getting 0V on the signal wire at the starter. My first thought was maybe a bad ground as many people have mentioned on youtube videos I have watched, so with the battery disconnected I cleaned and checked the grounds G105(transmission ground) and G103(body ground). The resistance I'm seeing on any ground in the engine compartment is about 0.006 OHMS.

After putting the battery back in, the car still did not start so I moved on to checking the voltages at the crank relay in the fuse box under the hood(with the crank relay removed). This is where I get a little lost. From the Autozone wire diagrams it looks to me like I should have 12V as a constant voltage to pin 30, and then 12V going to pin 86 of the starter relay only in start and in run, with the clutch pedal pushed in. So far, this is exactly what I am seeing. But for pin 85 of the starter relay(starter relay control side) I am seeing around 3V in start and in run. I would assume this should be open in run and 0V in start. These voltage measurements were taken with the G103 as a ground reference, and then I used the ground on the strut tower to double check. I assume that a 9V difference between pin 85 and pin 86 is not enough voltage to energize the relay to start the car.

What really confuses me is that in order to complete this circuit in run, it looks like the ECM has to make a decision in order to ground that connection(to pin 85) so I can have 12V supplied to the starter relay coil. I'm not quite sure what conditions the ECM is looking for in order to complete that connection and ground the circuit. Does anyone know? Should I be approaching this issue a different way?

Last edited by internetpimp; 03-30-2018 at 09:08 AM.
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post #2 of 18 (permalink) Old 03-28-2018, 04:04 PM
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Have you tried re-seating the BCM connectors? The BCM connectors are very prone to corrosion and I find this procedure to clear a lot of idiotic problems that don't seem to make any sense.

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post #3 of 18 (permalink) Old 03-28-2018, 05:26 PM Thread Starter
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I think I just read another post in here where you mentioned that. I did try disconnecting and reseating the J1 and J2 connectors on the BCM a few days ago. It wont hurt to try it again though.
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post #4 of 18 (permalink) Old 03-28-2018, 06:28 PM
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The BCM takes into account all sorts of things before it issues a start command. Maybe you'd need to re-seat all 4 connectors, one is on the backside. 9 Volts to me sounds like a resistive contact due to corrosion cause that's what it does.

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post #5 of 18 (permalink) Old 03-28-2018, 08:58 PM Thread Starter
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I haven't re-seated the connectors on the BCM yet, I will do that tomorrow. Just to be clear though, I did not measure 9V across the starter pin terminal 85 and 86 on the fuse block or on the relay, I measured 12V at pin terminal 86, and about 3V at pin terminal 85(the terminals where the relay plugs into). I assume the relay was getting 9V across these pins when in run/cranking, but I didn't measure across these pins, just each pin terminal in the fuse block individually to body ground.
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post #6 of 18 (permalink) Old 03-30-2018, 08:24 AM Thread Starter
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So I re-seated all 4 connectors on the BCM with the battery disconnected. While the battery was disconnected I did some extra diagnosing to make sure that there were no shorts or opens in the High speed and Low speed GMALAN, along with checking the continuity and resistance across the ignition switch connections. With all of that being said, on the crank relay connections in the fuse panel(with the crank relay removed), I am now getting +12V on pin 86, and 0V on pin 85, along with +12V on pin 30 with the ignition in start. Unfortunately the car still will not crank at all. I checked again the constant +12V and the signal wire. The constant 12V is there, but I am still not getting 12V on the signal wire at the starter, I'm still reading 0V. I swapped the relays with a sister relay in the fuse box, and still I get nothing. I took the relay out and energized pin 85/pin 86, sure enough I heard the relay clicking and the normally open contacts toggled closed(verified with ohm meter, 0.002 ohms or so). So next, I check across the battery for a drop in voltage, with the engine in start I get about a 2V drop across the battery terminals. So, with all of that being said, I'm now assuming that something in the starter solenoid is shorted. I'm really dreading having to pull off the starter to inspect as I don't have a floor jack to use at the moment. Anyone have any advice up to this point?

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post #7 of 18 (permalink) Old 03-30-2018, 03:30 PM Thread Starter
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Seems like I may be having similar problems that the guy is this thread had:

https://www.yourcobalt.com/forums/pro...-no-start.html

I kinda wish he would have came back and told us what the actual problem was..... :(
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post #8 of 18 (permalink) Old 03-30-2018, 05:32 PM Thread Starter
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Never mind, I don't have the exact same symptoms. The other guy was getting 12V on the start signal wire when it was disconnected, but 0V while connected. I'm getting 0V regardless if the signal wire is connected to the starter solenoid or not.

Still constant 12V @ Pin 30, 12V on Pin 86 and 0V on Pin 85 on the starter relay connections on the fuse block when the ignition is in start. I checked the resistance on the starter wire from Pin 87 to the end where it connects to the starter(with the wire disconnected from the starter) and it reads good, I also checked to make sure that this wire was not shorted to the engine ground, or any of the body grounds under the hood.

I'm now starting to think that something may have shorted out underneath the fuse block. Does anyone know of a better way of trying to diagnose this problem before I end up ripping out the fuse block under the hood?
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post #9 of 18 (permalink) Old 04-06-2018, 05:45 PM Thread Starter
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An update for anyone who cares.

I ended up using some alligator clips to check pin 85 and pin 86 of the crank relay while it is plugged in. When cranking, I expected to see a 12V drop across the relay coil when energized. Nope, 0V. With the relay still plugged in, I saw 12V on Pin 86, and 12V on Pin 85, which means that the circuit is not completing and the only thing left is for the ECM starter relay control to provide a ground on C1[Pin 31].

From what I read in the documentation in the Chiltons manual online, the only things that are needed for this is for the ECM to see 12V on the "Clutch Start Signal" C1[Pin 56] and a start signal from the BCM via the High Speed GMLAN(The initial signal is supposed to come from the Theft Deterrent Module to the BCM via the Low Speed GMLAN). I verified 12V on the ECM "Clutch Start Signal" C1[Pin 56] and had no control module communication faults which I would have expected to see if any control module was not communicating(via the OBD2 connection with scan tool). If the Theft Deterrent Module was not providing the correct signal to the BCM, I assume I should have had the security light pop up on the dash when trying to start.

Anyhow, during my diagnostic process, I ended up wiggling some wires around on the left side of the steering column (I already had the covers removed) and the car started the next time I tried to crank the engine. I could repeatedly start the vehicle a few times, but then I couldn't. After constantly wiggling more wires around and trying to start, the car started again. It was hit or miss after that and I could not narrow it down to one specific wire as there are a ton of wires in the suspected wire harness.

Apparently now it looks like I have a issue with the wiring near the steering column. I just don't understand logically how or what wire(s) would actually be causing this issue. I will update this post when I have more information, until then feel free to provide any additional help, or any input on anything that I'm wrong about, or something that I may have missed.
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post #10 of 18 (permalink) Old 04-07-2018, 05:21 AM
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Thanks for the update and good luck finding that loose wire...
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chevy cobalt , no start , pontiac g5 , starter relay , starter voltage




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