P0731 on Cadillac: How to Diagnose & Fix
Gear 1 Incorrect Ratio
1 Cadillac model · 1 documented issue · 1 critical · $600-$4,000 repair
P0731 on Cadillac by model: symptoms, diagnosis and fix
The 4T80-E four-speed used behind the Northstar develops two documented and related faults. The lower control valve body and its channel plate/gasket leak internal pressure, producing 1-2 shift delays, slips and flares with P0731 or P0732, and slipping or complete loss of fourth gear with P0734. Where the pressure loss has been present for a while, the fourth-gear (overdrive) clutch pack cooks off its friction material - owners report finding the pan full of clutch debris and the fourth clutch stripped bare. The transmission fluid pressure switch assembly sets similar codes and is a cheaper first suspect. Owners also report the plastic locating ears on the valve body breaking. Fluid contaminated with clutch material is what carries the failure across the rest of the clutch packs, which is why a late fluid change on a slipping unit often makes it worse rather than better.
Common Symptoms
- Slipping or no fourth gear / overdrive
- Delayed, slipping or flaring 1-2 shift
- Harsh or jolting shifts
- Check engine light with transmission codes
- Clutch material in the transmission pan
How to Fix
Scan the transmission and inspect the fluid and pan first. A clean-fluid pressure-switch or lower-valve-body fault may be serviced in-car; friction material or a lost fourth gear requires a rebuild or replacement unit.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Transtar/TransTec 4T80-E valve-body cover, spacer and channel-plate gasket set$18
1996-2005 Cadillac DeVille/Concours 4.6L 4T80-E branch. Gaskets only: the pressure-switch assembly, valve body and any fourth-clutch rebuild parts are separate and must be identified from the codes and transmission build.
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
Sources for this issue (3)
P0731 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0731 mean on a Cadillac?
P0731 stands for "Gear 1 Incorrect Ratio." This code means the Transmission/Powertrain Control Module detected an incorrect gear ratio in 1st gear. The module compares input (engine/turbine) speed to output shaft speed; when the car is commanded into 1st but the calculated ratio doesn't match the expected value, P0731 sets. This points to slipping, an incorrect shift, or a hydraulic/mechanical problem rather than just an electrical fault. You may feel slipping, harsh or delayed engagement, or the transmission may go into a limited 'limp' mode. On Cadillac it is documented across 1 model: DeVille.
What are the most common causes of P0731?
The most common causes of P0731 are: Low or degraded/burnt transmission fluid, Slipping clutch packs or worn friction components, Stuck or faulty shift solenoid affecting 1st gear, Internal hydraulic leak / valve body fault, Worn or failing torque converter, Faulty input or output speed sensor, Mechanical wear (planetary gears, bands) inside the transmission. The specific cause varies by vehicle.
How much does it cost to fix P0731 on a Cadillac?
Published repair estimates on Cadillac range from $600 to $4,000 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0731 on a different make?
View P0731 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.