2009 Cobalt 2.2 Ecotech Crank No start

Had A 2009 Cobalt brought in for timing chain and ignition issue.
Replaced Timing chain. Original Key broke off inside ignition so replaced the complete Ignition not just tumbler and programmed new key.
Still have a crank no start tested all relays and fuses have spark have fuel spark does seem weak but main issue I am having trouble with is with my scan tool hooked up to read codes but when I go to live data if i crank the engine i lose power to obd2 port and have to release the key back to on position to reconnect I have checked all relays fuses inside and out and also grounds on engine all seem tight and not broken what can cause a obd2 port to lose power only when cranking engine also tach does not move during cranking so main reason wanting to view live data is to see if rpm is moving any suggestions
ALSO lose power to cig lighter during cranking as well so am I missing looking for bad ground someplace ?

Do you lose power on all of these fuses?

yes it does wipers rear defrost radio aux outlet

yes I lose power to those only in crank position

Does the Starter turn the engine?

yes it turns just fine just loss of power to those fuses and relays during cranking and the no start of course

Hi everyone,

I have a similar issue with a chevy HHR (pretty the same circuit). If your car has battery in the trunk, look for main power cable which comes from battery (+) to hood fuse box or the one which comes from battery (-) to body chasis.

I had to add a #4 cable from battery (-) to block in order to improve ground and decrease electronic noises.

Also main power cable was completely corroded and broken.

Check also for voltage between battery (+) & (-). Then between hood fuse box voltage input & block.

Voltage should be the same.

You can discard my theory quickly, by adding a second battery connected in parallel like this:

Battery (-) to block and battery (+) to hood fuse box voltage input.

I would look at this splice, very closely.



Also, with the Negative Lead of your DVOM connected to Battery (-), touch the Red Lead to the Engine block while you are cranking. What voltage do you read? Touch the Red Lead to the Body, while cranking. What voltage to you read?

while cranking with no charger voltage drops from 12.5 to 10ish at battery and at post by fuse block I also ran jumper cables from battery to fuse block and to ground on shock tower with no difference where exactly would that splice be you circled

Did you read the voltage on the engine block, while cranking. I know this sounds funny. :blink: You wouldn't expect to ready ANY voltage on the engine block. But, If you have a bad engine ground, voltage cannot make it back to the battery. You WILL read voltage on engine block, with a bad engine ground. Same thing goes for the body.

where exactly would that splice be you circled

You'll have to follow the cable from the batter (+). I assume it will be very close to, or at, the fuse box. All I can say, for sure, is "Between the fuses and the battery. :huh:

touching the engine while cranking i get either .1 or .2 volts nothing on chassis

Well, that leaves us at that splice/junction.

Trace the cable FROM the BATTERY and the cable FROM the STARTER. Find where they meet.

thanks for the help Will check it first thing in the morning battery had died while trying so want it back up to full charge