Electrical start issue
- Thread starter DRL
- Start date
Aside from unplugging and replugging all connections…would you advise checking continuity of each connection? I suppose this is checking the electrical map and checking for appropriate resistance or continuity?
Have you confirmed every fuse on the main fuse panel and BCM is good?
If so, my first step would be to check every 12v supply wire on the ECM and BCM is getting power. I would do this by back probing the connector but that means you will need back probing ends for your DVOM. And use a 100% known good ground like a wire attached directly to the negative terminal of the battery.
If so, my first step would be to check every 12v supply wire on the ECM and BCM is getting power. I would do this by back probing the connector but that means you will need back probing ends for your DVOM. And use a 100% known good ground like a wire attached directly to the negative terminal of the battery.
yes. I have checked every fuse twice (and the important ones more). I will get some probing ends and start from there. I appreciate pointing me in any direction.
ah.b.normal
Goblin Guru
another troubleshooting item I performed:
Touched screwdriver to starter pos to ground to see if it would crank and no crank but spark.
[/QUOTE]
The test you described, "big post to ground", should always spark when grounded, indicating the battery is connected to the starter. The test you describe would NOT spin the starter over.
The big post on the starter should always be live because that big wire comes straight from the + post on the battery.
The second large wire on that post goes to the fuse box, at that funny tall jump starter bolt that sticks through the box cover and if it hasn't fallen off is covered with a red cap.
A smaller 10* wire off that post runs directly to the back of the alternator. There should be no other OEM wires on the large post on the starter.
The smaller purple wire, connected to the S terminal on the starter solenoid, "engages" the solenoid making the starter spin and is only "live" when the commanded by the ignition switch. It runs from the fuse box(probably directly from the starter relay) to the S terminal on the starter solenoid.
Please pardon me if you later did the starter test correctly and I have missed that post!
I am sorry if this all seems to be written for a complete novice; but I cannot always depend on everyone having my background on automotive systems.(and Ross makes me look like a hack!
) Having been my own mechanic for 40+ years, I realize simple, detailed explanation is best; but not always Short and Simple.
Touched screwdriver to starter pos to ground to see if it would crank and no crank but spark.
[/QUOTE]
The test you described, "big post to ground", should always spark when grounded, indicating the battery is connected to the starter. The test you describe would NOT spin the starter over.
The big post on the starter should always be live because that big wire comes straight from the + post on the battery.
The second large wire on that post goes to the fuse box, at that funny tall jump starter bolt that sticks through the box cover and if it hasn't fallen off is covered with a red cap.
A smaller 10* wire off that post runs directly to the back of the alternator. There should be no other OEM wires on the large post on the starter.
The smaller purple wire, connected to the S terminal on the starter solenoid, "engages" the solenoid making the starter spin and is only "live" when the commanded by the ignition switch. It runs from the fuse box(probably directly from the starter relay) to the S terminal on the starter solenoid.
Please pardon me if you later did the starter test correctly and I have missed that post!
I am sorry if this all seems to be written for a complete novice; but I cannot always depend on everyone having my background on automotive systems.(and Ross makes me look like a hack!
) Having been my own mechanic for 40+ years, I realize simple, detailed explanation is best; but not always Short and Simple.
Desert Sasqwatch
Bigfoot Goblin
Question: when this issue started you didn't happen to try to jump the fuel pump? Putting a jumper wire in the wrong location to run the fuel pump can burn traces on the circuit board in the fuse box. This has happened to a few builders and prohibits the fuel pump from running even though there is voltage at the fuse. Checking this requires looking for voltage from the fuse box going to the fuel pump connector, should be 12V.
Good thought. No. Different fuse box.
I am checking voltage in the BCM box. 12V on the right side. Only 0.6V on fuse 25 ECM/TCM. I’m going to try and look if this is normal unless anyone easily knows answer
If the fuse has only voltage one side it's usually defect.
Fuse 25 should have 12V on both sides.
Replace the fuse.
Electrical Diagrams — 2009 Chevrolet Cobalt L4-2.2L Service Manual | Operation CHARM
Detailed repair manual for the 2009 Chevrolet Cobalt L4-2.2L.
charm.li
As I continue to try and learn how to read a wiring diagram I kept connecting things I knew…
don’t know why but when I connected headlights and only when they are on, OBD2 now gets power and I was able to connect. Passkey light also comes on and stays on now. I have tried twice to due the relearn (4 cycles each) without success but I still have hope - just ran out of time.
will start reviewing codes:
don’t know why but when I connected headlights and only when they are on, OBD2 now gets power and I was able to connect. Passkey light also comes on and stays on now. I have tried twice to due the relearn (4 cycles each) without success but I still have hope - just ran out of time.
will start reviewing codes:
Couple of related threads
dfkitcar.com
dfkitcar.com
No Crank when Headlights off
I’m probably missing something really stupid here. Has anyone experienced a no crank unless the headlights are on?
No Start Issue - B+ Terminal/Fuse Box
It could be a bad/missing ground that ends of grounding through the headlight or relay once the lights are turned on.
Making progress but still no crank.
probed plugs at BCM and confirmed all ground intact. Identified missing power from battery and was able to trace to bad splice of power connector/cable to BCM. So there was power back feeding somehow. Put everything back together: turn signals and flashers now work correctly but OBD no longer connects (with or without headlights).I confirmed all fuses intact.
I notice that my tail lights are staying on with and without headlights and do not get brighter with brake pedal depressed. Potential issue to trace. Any ideas?
otherwise I plan to continue to check power/grounds to plugs at BCM and PCM (while I continue to learn how to trace wires based on diagrams).
probed plugs at BCM and confirmed all ground intact. Identified missing power from battery and was able to trace to bad splice of power connector/cable to BCM. So there was power back feeding somehow. Put everything back together: turn signals and flashers now work correctly but OBD no longer connects (with or without headlights).I confirmed all fuses intact.
I notice that my tail lights are staying on with and without headlights and do not get brighter with brake pedal depressed. Potential issue to trace. Any ideas?
otherwise I plan to continue to check power/grounds to plugs at BCM and PCM (while I continue to learn how to trace wires based on diagrams).
ah.b.normal
Goblin Guru
There is something wrong here and it is basic. I just know it! I'm betting Fuse box. Something cross connected? Maybe something conductive rattling around under the fuses on the circuit board? It is possible to install some of the relays in holes that are beside the correct holes. Not easy to do but I found one relay stabbed into four holes, just half were for one relay and half an adjacent relay spot. Ham fisted folks can do amazing things! Bent/loose connector on the engine harness multiplug(black rectangular box) under the fuse panel? Have you checked for a bent prong where that plugs in underneath?
You are learning a lot about reading wire diagrams and diagnosing electrical, I just wish it was under better circumstances! Pressure to find this problem is probably making you a little nuts. NOT a new thing, it always does. Patience and listening to the guru's on this forum will lead to success, Sadly, a quicker route is to involve an auto electric mech to look directly at the unit. (And those guys get paid well.)
You are learning a lot about reading wire diagrams and diagnosing electrical, I just wish it was under better circumstances! Pressure to find this problem is probably making you a little nuts. NOT a new thing, it always does. Patience and listening to the guru's on this forum will lead to success, Sadly, a quicker route is to involve an auto electric mech to look directly at the unit. (And those guys get paid well.)
Thank you for the support! You summarized my journey well. I scheduled a mechanic for this weekend …then postponed when I started to make progress. It’s not the money so much as the pride!
ah.b.normal
Goblin Guru
I went back a reread this post. Is this correct? The engine wire harness is from an N/A motor? The fuse box and the rest of the wiring is from an SS?
Engine wiring harnesses are not usually interchangeable between engine sizes. This stuff changed almost yearly. An SS engine harness has circuits an N/A motor does not have. Intercooler pump, VVT?, a second cam sensor, A mystery sensor by the turbo?(Mystery to me! I know one is there that is not on any N/A motors harness), etc.
Compare the wire positions on the big black block connector on both harnesses and make a chart of the connector positions on each(note wire color and size). Each row down is numbered and across is lettered. Holding the block in your hand the letters/numbers are molded into/on the side that the wires go into the block, not the face that connects to the fuse panel bottom. The numbers/letters are very small, use a magnifying glass if needed.
Engine wiring harnesses are not usually interchangeable between engine sizes. This stuff changed almost yearly. An SS engine harness has circuits an N/A motor does not have. Intercooler pump, VVT?, a second cam sensor, A mystery sensor by the turbo?(Mystery to me! I know one is there that is not on any N/A motors harness), etc.
Compare the wire positions on the big black block connector on both harnesses and make a chart of the connector positions on each(note wire color and size). Each row down is numbered and across is lettered. Holding the block in your hand the letters/numbers are molded into/on the side that the wires go into the block, not the face that connects to the fuse panel bottom. The numbers/letters are very small, use a magnifying glass if needed.