P0976 question

[skynyrdcat]

i HAVE THE DREADED 976 on an 07 cobalt 2.2.

When I check the trans fuse in the engine compartment I have 11.3v on one side ans 1.7v on the other side.

I assume that it's a short since it's hot on both sides, just wanted to get some other opinions on it.

Thanks in advance.

[cobalt123]

bump

[Tuner923]

Originally Posted by skynyrdcat i HAVE THE DREADED 976 on an 07 cobalt 2.2. When I check the trans fuse in the engine compartment I have 11.3v on one side ans 1.7v on the other side. I assume that it's a short since it's hot on both sides, just wanted to get some other opinions on it. Thanks in advance.

not necessarily a short...

there's not really a lot of info to go from here.. so

now If you are talking about some voltage on the ground after the "load" that is a sign of high resistance on the ground wire. more than likely meaning that there is a bad/corroded connector or the mount to ground is corroded or possible the ground wire is frayed or pinched...

how are you checking this.. where are you placing each lead of the meter? I really hope you are using a digital meter and not an analog voltmeter.

[skynyrdcat]

Originally Posted by Tuner923 not necessarily a short... there's not really a lot of info to go from here.. so now If you are talking about some voltage on the ground after the "load" that is a sign of high resistance on the ground wire. more than likely meaning that there is a bad/corroded connector or the mount to ground is corroded or possible the ground wire is frayed or pinched... how are you checking this.. where are you placing each lead of the meter? I really hope you are using a digital meter and not an analog voltmeter.

Digital yes.

I removed the trans fuse, put the blk dmm lead on the neg battery post and put the red on either fuse terminal. I have voltage on both terminals less than 12 on the IN side and over one on the OUT or trans side

[Tuner923]

I'd say next place to look is all wiring to the 2-3 Shift Solenoid

[skynyrdcat]

If I'm getting less than 12 to the fuse could that be the problem? The TCM is supposed to give ignition voltage to the 1-2 and 2-3 solenoids, and control them by providing a ground path for either. Ignition voltage would be 12.5v right?
I found where the harness was rubbing the corner of the bell housing and fixed it, so I only have power on the input side of the fuse now, but still less than ign voltage (11.7 now) would that be enough to trigger the codes / no shift?

I plan to check the TCM harness for voltage on the #2 (1-2 solenoid), #31 (ign voltage from fuse) and #20 (2-3 solenoid) wires, as soon as weather and time permit. But, if I only have 11.7 going to the TCM, I don't think I'd expect to see 12.5 going to the solenoids.
Any thoughts?
Assuming I find 11.7 going to the solenoids, should I try a fused jumper from bat + to the #31 wire?

[Tuner923]

Originally Posted by skynyrdcat If I'm getting less than 12 to the fuse could that be the problem? The TCM is supposed to give ignition voltage to the 1-2 and 2-3 solenoids, and control them by providing a ground path for either. Ignition voltage would be 12.5v right? I found where the harness was rubbing the corner of the bell housing and fixed it, so I only have power on the input side of the fuse now, but still less than ign voltage (11.7 now) would that be enough to trigger the codes / no shift? I plan to check the TCM harness for voltage on the #2 (1-2 solenoid), #31 (ign voltage from fuse) and #20 (2-3 solenoid) wires, as soon as weather and time permit. But, if I only have 11.7 going to the TCM, I don't think I'd expect to see 12.5 going to the solenoids. Any thoughts? Assuming I find 11.7 going to the solenoids, should I try a fused jumper from bat + to the #31 wire?

so you found a short on the wire to ground? Has the code gone away since finding the wire rubbing on the bell housing. That would cause a low voltage at the solenoid.

I meant to go into all data and shop key today but it slipped my mind today. I am going to set a reminder on my phone and print out a bunch of the wiring diagrams and related info. it's kinda hard to do this without it in front of me.

Jumper wires are intended to find an open in a circuit. but if fuse os the same amp rating or lower should be safe

out of curiosity what is your battery voltage KOEO? If it's 11.7v it would explain why you are not getting 12.5v at the fuse.

[skynyrdcat]

Originally Posted by Tuner923 so you found a short on the wire to ground? Has the code gone away since finding the wire rubbing on the bell housing. That would cause a low voltage at the solenoid. I meant to go into all data and shop key today but it slipped my mind today. I am going to set a reminder on my phone and print out a bunch of the wiring diagrams and related info. it's kinda hard to do this without it in front of me. Jumper wires are intended to find an open in a circuit. but if fuse os the same amp rating or lower should be safe out of curiosity what is your battery voltage KOEO? If it's 11.7v it would explain why you are not getting 12.5v at the fuse.

Some of the all data stuff doesn't line up... Some diagrams show the circut with a 15a fuse, some show it with 10, etc and one diagram will show RD/WH wire color and the next show a different color.

I'll check the battery voltage when I get home. I think I checked it but didn't pay much attention because it was normal. If it had been low I'd have taken notice.
Anyway, more info to come this evening.

[skynyrdcat]

Battery voltage 12.0.

IGN to TCM 11.8

TCM to 1-2 solenoid = .2v

TCM to 2-3 solenoid = .3v

I'm thinkin the TCM is shot. It should have ignition voltage to both solenoids with the key on, and then ground one of them accordingly. If I have power to the TCM and none coming out, I think that constitutes springing the $50 for a TCM.

[YelloEye]

I assume you have the wiring schematic in front of you?

If not it's worth it to get the service books and or have someone else take the same readings on their car.