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Thread: 4L80E only first and reverse gears

  1. #1
    Join Date
    Feb 2007
    Baja California Sur Mexico

    Default 4L80E only first and reverse gears

    Without any previous trans symptoms, the truck, in the morning wouldn't change out of 1st gear, had codes 81, 2-3 solenoid circuit, and 84, throttle pedal circuit. Problem cured after days of internet searching, testing voltage at trans plug, solenoid activation, input speed sensor, changed the throttle assembly, still code 84. Codes 81,82,83,84, now occurred without starting the engine, cleared, then 84 wasn't there. Swapped in the computer (ECM) from the other vehicle and no codes. Plugged the original one back in, no codes, went for a drive, got the gears back. Most of the time was spent searching the internet for similar problems, which got me to change the ECM, and also plug the old one back in. Hope this helps other people, no money spent. That is why I choose to have two identical vehicles.
    Grant H.
    1995 6.5 turbo GMC K2500 extra cab 4x4 pickup, PMD under bumper, mechanical wastegate, 228,000 miles, rebuilt engine, 4.10 diff, 16 mpg
    1994 6.5 turbo GMC K2500 4x4 suburban "F" VIN #9 resistor, PMD in the bumper, mechanical waste gate, 226,000 miles, Positrac 3.73 diff, 17 mpg highway.
    1982 4x4 shortbed 6.2 Chev 260,000 miles untouched motor 17 MPG 4.27 diff. Best thing I ever owned, 21 years.

  2. #2
    Join Date
    Sep 2007


    WOW! Good information, thanks.
    1997 Silverado 1500 6.5. with 185,000 miles. New fuel injection pump at 132,000 mi. FSD Heat-Sync in bumper hole, marine fuel injectors, air induction kit all from Walt at 148,000 mi. Replaced OEM Fuel Filter Assy, wastegate solenoid valve, OPS and relay at 155,000 mi. Harmonic Balancer replaced. Red dot and White dot EGR replaced. New starter, Instant Heat glow plugs, and glow plug relay/controller at 180,000. Replaced hydroboost and master cylinder in 2016.

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