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2011 GMC Sierra 5.3L 6L80E Transmission Limp Mode with P0702 Code After Debris Damage

Model: 2011 GMC Sierra Fault Code: P0702 Posted: 2018-12-01 20:40

I own a 2011 GMC Sierra SLE with a 5.3L V8 and 6L80E transmission, currently at 188,000 miles. The vehicle has been well-maintained with regular servicing and no prior issues until now. After hitting a deer, I damaged the transmission fluid line and lost approximately 6 quarts of automatic transmission fluid (ATF). Following this, the transmission entered limp mode and triggered a P0702 diagnostic code. I refilled the transmission with 6 quarts of Dexron VI ATF, which was recently changed about 15,000 miles ago—so I know the fluid is not degraded. However, I now observe noticeable gear slippage between 2nd and 3rd gears, as well as 3rd and 4th gears. The issue appears to be persistent even after refilling. Is this a solenoid-related problem or could it be due to internal transmission damage from the fluid loss?

Related fault codes
P0702
Comments (5)
Anonymous 2018-12-02 08:28

P0702 is a generic OBD-II code often associated with transmission issues, similar to the older P0700. I should verify this—does your vehicle show only P0702 or are there any additional codes? The 8th digit of the VIN indicates whether it's an engine or transmission variant (0 or 3). Could you confirm that? Also, did you use the correct ATF type—Dexron VI is recommended for this application? If the transmission is truly slipping, I’d expect more diagnostic errors. Have you used a dedicated transmission scanner to check for deeper faults?

Anonymous 2018-12-02 14:17

The engine code is 0. The original error message mentioned 'Solenoid A' and 'Solenoid B,' but I didn’t save it. I filled the system with Dexron VI ATF, and the slippage became apparent after refilling. Since my last ATF change was at around 15,000 miles ago, I’m confident the fluid isn't dirty or degraded.

Anonymous 2018-12-02 14:24

I'm using an OBD-II code reader. On a scale of 1 to 10, when the transmission is cold: 2nd to 3rd gear operates smoothly (score 2), while 3rd to 4th shows about a 4-point slip. When warmed up, 2nd to 3rd slips slightly (about a 2), but 3rd to 4th increases significantly to around a 6. I suspect some unusual downshifting behavior, though it's not extremely noticeable. Thanks for the input!

Anonymous 2018-12-02 14:28

I cleared the P0702 code, and since then, no new codes have appeared—though physical symptoms like slippage remain.

Anonymous 2018-12-02 16:12

Consult your transmission overhaul manual. You will need a dedicated transmission-capable scanner to properly diagnose this issue. I suspect your current OBD-II reader lacks the necessary depth to detect internal solenoid or hydraulic faults—this is critical for accurate diagnosis.