Wire harness Ground Issues 09-LS
 

OK, so i had to replace an engine wire harness (the monster that connects to everything) and it isnt working since i finished. I tried to double and triple check every connection, and i am stumped. There is a small ground off the harness at the top back of the engine right off the top right corner (as viewed facing the engine!) - and it isnt grounded. The big ones that attach behind the alternator and behind the radiator into the top of the tranny casing are not grounding! What am i missing?

The computer wont communicate with an OBD scanner and it wont even click at the starter. All the connectors seem to be tight, and it is a brand new harness that was matched to the vin.

Anyone with ideas? A ground for the engine that went bad? Previous issues that fixed something like this? My uncle who is a retired mechanic and myself a long time hobbyist are stumped! (Grant you our experience is mostly cars with minimal electronics) HELP!!

The one on the rad support and the one on top of the trans are connected. The rad support is the "main" ground.

You remembered to hook the battery back up?

What was wrong to begin with?

i had no signal to several wires throughout the harness. It was losing power as soon as it was warm. we also had a leak at the valve cover and that was fixed. We started testing wires to track down the problem, there were multiple either no signal or intermittent signals suggesting an incomplete break in the wire! All three ground points dont have a solid ground. Tried testing with different meters and nothing connected to the engine seems to provide any ground!

Is there a ground that is not part of the harness than connects the engine/tranny to the body to ground?

This might help.

https://www.chevyhhr.net/forums/how-...cations-56504/

Yep. There is a single seperate ground wire as Don mentioned before. One end is at the radiator core support(left side of car near the AC line) other end at the trans.

found ground - still no start!
 

So the ground was buried looking like it was attached but just sitting there! I connected it and all the power and grounds seemed fine - but nothing at the starter. Computer connects (Huge improvement) but with the engine not running it gives me little relevant data!

Tried a jump - just in case the battery had dwindled. No response!

Do i replace the starter? Is there some other connection i may have missed? Pulling my hair out, and my uncle with 40 years experience is stumped!

The main power wire to the starter comes straight from the battery. It's always hot. Are you saying there is no power to that cable ? If no power at the starter, time to get out the volt meter or test light and find where the break is.

Currently, the battery died and wouldnt even offer a hint of a groan at the starter when we tried jumping it. Battery out for the night to charge up (No garage to leave charger in.) Not sure why battery died, but we are going one step at a time. After charging, any suggestions on where to start?

As FMG said - "If no power at the starter, time to get out the volt meter or test light and find where the break is." Check the voltage at the starter while attempting to start it.
If power is getting to the starter, you can try jumping the starter solenoid to get it going - but the starter would need replacement.

If it wouldn't start with a jump (assuming it was hooked up correctly with the Neg attached to one of the strut studs on the inner fender), then you obviously still have problems.
Once the battery is charged, give it a try, also monitor the battery voltage when you start or attempt to start it.

The large red wire to the starter comes from the battery via the jump point on the fuse box, then goes to the alternator (always HOT). the starter is grounded to the bell housing. The wire to the solenoid comes from the fuse box.

I am thinking a total mis diagnosis. Did you think to check the connectors on the bottom of the fuse box?

OK, sorry for delay in response, cut computer cord on edge of tool box. . .thats my kind of luck!

So we have checked the starter, the battery, the fuse panel, the grounds. . .i tried to take everything apart and put it together double checking every step!!!! I am ready to fill the car with dynamite - except my wife LOVES the car!

The problems seem to all tie to the ECM at this point - it is the only common circuit among all the places not working right now! Last january - i had a problem with the steering not working and we went through a similar problem, but the mechanic who helped us then left the area so we cant even try to figure out what he did! Is there a diagram of the ECM wiring or is it just overlay the whole set from the Haynes Manual?

THANKS!! My sanity is being tested - I'm hoping the car can be resurrected before i am bald!

What was the "problem with the steering"?

If it was randomly going out, then coming back on the next key cycle; a good mechanic would have told you to go to a GM dealership and take advantage of the FREE special warranty.

I don't know if you are ignoring us or just not mentioning it. Does your post under the red cover look like the pic in post #11? Did you check that for 12V, then check the end at the starter for 12V then the end at the alternator for 12V?

Has the ignition recall been done?

Sorry, not ignoring, just overlooked in reply! The Power supplies look the same, and test around 11.8 volt after testing and trying to start for 2 days without charging! (had been 12.07 when battery first put back in!)

As for the steering issue, it started out by just randomly kicking out while driving, and progressed to not kicking in at all on some starts! We disconnected everything to the steering, reset it all - changed fuses and relays. . . We never changed any parts at that time!

Presently - there is power everywhere - but power from the fuse panel to the ECM seems to be interupted. The starter has power, the solenoid tested OK. Voltage seems to be right most places. the one thing not right is the ECM fuses in the underhood panel have low (3v) or no reading! took panel out to check it is tight but nothing seems loose and after restoring it we still had no power.

Cant figure out where to look next.

11.8V and 12.07v?? that is too low. What were the readings after it was charged?

There is a special warranty on the power steering motor. Get it fixed for FREE at GM.

Are you looking at wiring diagrams? Some of the circuits are 5V, some of the fuses are on the ground side. What specific fuses are you testing, they have numbers. The connectors all have pin numbers.

Did you go back to the connectors on the bottom of the fuse box?

Fuse #25 on the BCM (inside) supplies 12V to the ECM.

Is there 12V on both sides of fuse #5 underhood?

41, 43, 45, 46 all test low or no power! Key on/off/crank. . .no change in power at them!

is there a single schematic that might show all the overlaps from the ECM rather than looking at all the schematics separately?,

FUSE #25 on the BCM!!!! The fuse box inside the car on the passenger side under the radio.
In my book (Mitchell OnDemand) there is a 4 page diagram entitled "2.2L VIN B, Engine Performance Circuit"

Check your PM.