Gear 1 Incorrect Ratio
The DURAMAX-P0731 (Duramax) diesel fault code means: Gear 1 Incorrect Ratio. This is a serious severity code.
- Keep driving?
- Yes, with caution
- DIY difficulty
- intermediate
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What Are the Symptoms of DURAMAX-P0731?
- Check Engine Light on
- Slipping, flare or harsh shifts
- Transmission may hold a single gear
What Causes DURAMAX-P0731? (Most Likely First)
- Low or degraded transmission fluid High
- Internal clutch wear or a hydraulic fault Moderate
- Faulty input or output speed sensor reading Moderate
- Shift solenoid fault Low
Can I Still Drive with DURAMAX-P0731?
Yes, with caution. DURAMAX-P0731 is rated serious severity. Keep trips short and get it diagnosed soon rather than waiting for symptoms to worsen.
Frequently Asked Questions
What does P0731 mean on a Duramax?
P0731 means Gear 1 Incorrect Ratio. In gear 1, the transmission control module sees a ratio between input and output speed that does not match that gear.
Is P0731 a Duramax-specific code?
No. P0731 is a generic OBD-II code defined by SAE J2012, so it means the same thing on any vehicle that sets it. The exact conditions GM uses to set it on its diesels are in GM service information.
Mechanics Guide Step-by-step diagnosis
How Do You Diagnose DURAMAX-P0731?
Check the transmission fluid level and condition first.
Compare input and output speed readings on a scan tool in the affected gear.
Check for speed sensor and solenoid codes, which can cause a ratio code.
Sources 1
This page is built from documented references. Verify against your own service info before repair work.
- SAE J2012Diagnostic Trouble Code Definitions (defines P0731 as a generic OBD-II code)
P0731 on Other Platforms
The same code ID appears across other engines, vehicles, and equipment. Diagnostic flow varies by platform — see the matching breakdown:
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