Need helps

[LQ4-TURBO]

I swaped to a 4l80e and I checked my truck for codes because when I went to put in gear the the gear selecter on the dash said it was in reverse but the truck wanted to move forward but not much even when I pressed on the gas peddle. Also the truck will stay idle but it sounds like it has a knock may e fuel related? Oil pressure is good.

The codes are
P0134 o2 senser bank 1
Po154 o2 senser bank 2
P0740 torque converter clutch solenoid circuit open
P0785 shift timing solenoid malfunction
P0134 02 senser bank 1 no activity
P0154 02 senser bank 2 no activity
P0740 torque converter clutch solenoid open
P0785 shift timing solenoid malfunction
P1810 DTC definition not found see service manual

I'm thinking when I downloaded the new tune it erased the codes?
I bought new 02 sensors and a new neutral safety switch for the gear selecter for the side of the trans. I then down loaded the new tune with the updated 4l80e segment swap.

The truck shows no codes but it still dosent want to move much and when it showing reverse the trucks feels like it wants to go forward?

Also one of my biggest headaches is the the bracket the holds the shift cable which one do I need I been having to have a friend hold the brake while I claim into the truck and manually switch the gears.

[LQ4-TURBO]

Well I've been doing a little research on my various codes and several places that I have read are saying that it could be the IGNITION SWITCH?

"The most likely cause of this condition may be a loss of power to the transmission on circuit 1020. This loss of power may be caused by an open in the ignition switch. This condition may also be the result of an incorrect installation of an aftermarket electronic device such as a remote starter or alarm system."


With the ignition switch in the RUN position, test for battery voltage at the appropriate fuse shown.

"If battery voltage is present at the fuse, inspect circuit 1020 between the fuse and the transmission for possible opens. If battery voltage is not present at the fuse, replace the ignition switch using the Ignition Switch Replacement procedure in the Steering Wheel and Column sub-section of the applicable Service Manual. Refer to group number 2.188 of the parts catalog for part description and usage."






Have any of you ran into this problem before and does it seem right.

Where is circuit 1020 located at?

The link

Trouble Code: P0785

Any help would be greatly appreciated, thanks!

[LQ4-TURBO]

Well I checked the ignition fuse and circuit 1020 but they where both good I also checked the trans pump and it was good. When I checked for circuit 1020 I pulled the ignition fuse and tested for power right at where the fuse clicked in and got about 11.20 volts I thought that was good? Am I tested the right circuit?

Should I replace the ignition switch?
Please help I've had this truck for over 2 years and only drove about 300 miles!

[Ray@NP]

First what is the year, make and model of the truck?

[LQ4-TURBO]

2000 Gmc sierra
I'm not home right now but I believe its an SE model
Its got an 6.0 and 4l80e swap

From all the research I've been reading with the codes I have, I think its the ignition switch? I'm almost 100% positive that's its NOT something internal with the transmission. Does the truck need to be tuned for the 4l80e to change into the proper gears? I know that it will need to be tuned in general for the 4l80e swap but when I manually get under the truck and place it into reverse it doesn't what to move. When I press on the gas its trying to move forward even though its in reverse?

I appreciate any help from you guys!

[LQ4-TURBO]

OK am a little confused I've had several people tell me conflicting answers.

If I got a segment swap down on a 4l80e would the trans shift like normal or would it still not shift right tell after it has been tuned? I'm not sure to pay for a trans tune or order an ignition switch etc?


One more thing the truck has been tuned for the engine that's in it but it doesn't what to idle sometimes it will sometimes it wont. When it does idle if I press on the gas it will wont to die. When this info and all the codes that I have could this be something else not related to tuning? Meaning would these codes show up if you swapped in the 4l80e and the truck hasn't been tuned for the 4l80e or could it just be that it might need a ignition switch or something else?

Thanks