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2004 Chevy Avalanche P0740/P0753/P0758/P0785/P0761: Transmission Solenoid Faults After Adding LED Floor Lights

Model: 2004 Chevy Avalanche Fault Code: P0740 Posted: 2016-09-02 14:36

I recently installed LED strip lights on the floor of my 2004 Chevy Avalanche using a fuse adapter connected to the IGN0 (10A) fuse in the interior panel. The next day, after attempting to drive the truck, the Check Engine light came on and I noticed the vehicle feels stiff and sluggish—like it's stuck in first gear—even though I'm not sure which gear it's actually in. After stopping at a sign or pulling out from a stop, there’s a noticeable delay before power builds up, and the transmission doesn’t seem to shift into second or third gears as smoothly as before. After a few seconds, it eventually shifts normally, but the transition feels abrupt and unnatural. I’ve been researching the error codes that appeared: - P0740: Torque Converter Clutch Solenoid Circuit Fault - P0753: A/T 1-2 Shift Solenoid Circuit Malfunction (4L60-E, 4L80-E) - P0758: A/T 2-3 Shift Solenoid Circuit Malfunction (4L60-E, 4L80-E) - P0785: A/T 3-2 Shift Solenoid Circuit Malfunction (4L60-E, 4L65-E) - P0761: Torque Converter Clutch Pressure Control Solenoid Fault These codes suggest a transmission solenoid issue. I’m wondering if connecting the LED lights to the IGN0 fuse caused a short or blown fuse, or whether all my transmission solenoids need replacement. I’ve confirmed that the truck has an alarm and starter system from 2004, which may be relevant for power distribution. Could the lighting installation have triggered the vehicle’s LIMP mode? I’m looking for guidance on how to safely add electrical accessories without causing transmission or ECU errors.

Related fault codes
P0740P0753P0758P0785
Comments (13)
Anonymous 2016-09-02 14:55

The transmission has likely entered LIMP mode, operating in a single gear. First, disconnect the LED lighting system—this was likely the root cause. Check the IGN0 (10A) fuse: is it hot on both terminals when the engine is running? The IGN0 fuse powers all transmission solenoids, so tapping into it can trigger faults.

Anonymous 2016-09-02 20:03

I made a critical error by using that fuse adapter. I assumed it wouldn’t cause damage since it was just an adapter. After removing the LED adapter and reconnecting the original 10A IGN0 fuse, both terminals show power when running—this suggests the issue may have been caused by overloading or improper voltage draw.

Anonymous 2016-09-03 06:59

With the new fuse installed, how does drivability feel? It should shift gears properly. The Check Engine light might stay on briefly but should eventually turn off. If shifting is still delayed or absent, try clearing the codes and test driving to allow the transmission to relearn gear shifts. Expect a slight delay in shifting as it recalibrates.

Anonymous 2016-09-03 07:40

The truck now shifts correctly—after a drive around my property, it transitions smoothly between gears. The shift timing is slightly delayed at first, but after passing several stop signs, the behavior returns to normal. Notably, when starting the engine, it initially feels weak and 'lazy' before gaining full power. The Check Engine light turned off after I replaced the fuse and started the truck two or three times—this was a key indicator that the issue was resolved.

Anonymous 2016-09-03 07:49

For persistent hard starting, check fuel pressure using a gauge. Are you still using the Christmas tree lighting system? A wiring diagram would help identify safe 12V power sources. Can you use a test light or DVOM to verify voltage at different points? This will assist in safely powering LED lights without triggering ECU faults.

Anonymous 2016-09-03 08:12

I’m currently checking this! I can read wiring diagrams and have a test light. I need to find a safe 12V fuse slot for the LED floor lights—ideally one that doesn’t use an active circuit. The adapter is grounded to a bolt (negative), and the positive side connects to the fuse. If it continues to cause errors, I’d prefer not to install them—but if possible, I’d like to keep the lights on.

Anonymous 2016-09-03 08:33

Check the 'SEO ACCY' fuse in your wiring diagram (available at http://www.revbase.com/BBBMotor/Wd/DownloadPdf?id=80939). This fuse should be unused—does it have a 10A fuse? Is it labeled as an accessory or upfitter fuse?

Anonymous 2016-09-03 09:12

I’ve confirmed: the SEO ACCY fuse slot has a 10A fuse in place.

Anonymous 2016-09-03 10:26

Consider using an unused, non-critical circuit—such as 4WD or trailer power—instead of tapping into IGN0. The IGN0 fuse is critical and powering transmission solenoids; adding load without proper knowledge can cause ECU faults or LIMP mode activation.

Anonymous 2016-09-03 11:00

The 4WD system has a dedicated fuse, and the wiring diagram confirms this. Can I safely connect the LED adapter to the SEO ACCY or 4WD fuse? Or should I use an unused fuse slot with no active load—ensuring it’s not powered during operation?

Anonymous 2016-09-03 11:13

It's not a simple fix: even if a fuse is unused, verify whether it remains hot in 'run' or only during start. Check the power source upstream of the fuse. Also, why did adding wiring cause a blown fuse? Is the lighting circuit itself faulty? Try an unused fuse slot—but always test for voltage and current before connecting.

Anonymous 2016-09-03 11:31

The SEO ACCY is labeled as 'Special Equipment Option - Accessory' (upfitter). I tested it—when the engine is running, both terminals show power. The lights work fine with no errors, and the wiring is properly grounded. This confirms that the lighting circuit is safe. However, tapping into IGN0 caused a fault because that fuse powers transmission solenoids. Using SEO ACCY may be safer. Thanks for your detailed troubleshooting—this helped me resolve both the LIMP mode and LED installation issues.

Anonymous 2016-09-03 13:57

SEO ACCY is an accessory fuse, often used for upfitter items like flashers or radios. Try using that slot—it’s a safer option than tapping into IGN0. Enjoy your lights—just keep the wiring diagrams handy for future modifications.