P0829 code definition
The P0829 code is a generic powertrain code related to the transmission, including pressure faults and sensor failures. In this case, the vehicle's engine control module (ECM) has found a fault in the 5-6 shift function.
Codes related to the P0829 include:
- P0729: Gear 6 Incorrect Ratio
- P0730: Incorrect Gear Ratio
- P0731: Gear 1 Incorrect Ratio
- P0732: Gear 2 Incorrect Ratio
- P0733: Gear 3 Incorrect Ratio
- P0734: Gear 4 Incorrect Ratio
- P0735: Gear 5 Incorrect Ratio
- P0736: Reverse Incorrect Gear Ratio
What the P0829 code means
A P0829 code is stored when the ECM detects a problem with the vehicle shifting into Gears 5 and/or 6.
When a vehicle has a computer controlled automatic transmission, it uses shift solenoids to manage fluid transfers between the hydraulic circuits. This then actuates a change in the gear ratio in the transmission. Changing the gear ratios allows a vehicle to change speed.
Calculations using throttle position, engine load, and engine and vehicle speed help the ECM ascertain the correct gear ratio. Note, manufacturer code parameters vary (be sure to check your vehicle service manual or YourMechanic for specifics to your make and model). If the ECM detects a different gear ratio than the one it desires relating to the 5 and 6 gears, a P0829 code can be stored.
What causes the P0829 code?
Several problems may cause a P0829 code including:
- Transmission fluid may be low
- Transmission fluid may be dirty or contaminated
- Damaged or defective shift solenoid
- Internal transmission fluid passages may have hydraulic blockages
- Damaged or defective transmission control module
- Damaged or defective ECM (rare)
What are symptoms of the P0829 code?
Symptoms of a P0829 code may include:
- There may be no symptoms at all aside from a stored code
- A check engine or warning light may illuminate
- The vehicle many not shift
- The vehicle still shift, but very roughly
- The vehicle may exhibit signs of transmission slippage
- Decreased fuel economy
- Vehicle may enter “limp” mode
How does a mechanic diagnose the P0829 code?
A mechanic may use several methods to diagnose a P0829 trouble code, including:
- Utilize an OBD-II scanner to check for a stored P0829 trouble code
- Check the transmission fluid level
- Check the transmission fluid quality, checking transmission pan for debris (which can be the sign of a larger problem)
- Visually inspect the system circuitry and wiring for obvious signs of damage, corrosion, or wear
- Check for any possible transmission fluid leaks
- Use a manual pressure gauge to check pump pressure, comparing to manufacturer recommended levels
- Check for damaged or defective pump
- Check for damaged or defective electronic pressure regulator
- Check for damaged or defective shift solenoids by testing for reference voltage and ground signals
- Check all circuits in the 5-6 shift solenoid for continuity and resistance
Common mistakes when diagnosing the P0829 code
If the transmission fluid is low or dirty, it could cause insufficient fluid pressure and store the P0829 code. It is recommended to check and flush or fill a vehicle’s transmission fluid before proceeding with any subsequent diagnosis and repairs.
How serious is the P0829 code?
Because a vehicle’s safe driving operation may be impacted due to faults that store a P0829 code, this code is considered a potentially serious code. When this code appears, it is recommended to immediately take your vehicle to your local service center or mechanic for repair and diagnosis.
What repairs can Fix the P0829 code?
Several repairs can fix a P0829 trouble code and include:
- Fill the transmission fluid to manufacturer recommended levels
- If needed, perform a full flush on the transmission fluid
- Repair or replace any damaged, burned, or corroded wiring, connectors, and harnesses
- Repair any leaking hoses and related components
- Repair or replace damaged or defective pump
- Repair or replace damaged or defective electronic pressure regulator
- Repair or replace damaged or defective shift solenoids
- Replace damaged or defective transmission control module
- Replace damaged ECM (rare)
- Clear all codes, test-drive the vehicle, and rescan to see if any codes reappear
Additional comments for consideration regarding the P0829 code
Additional shift solenoid-related trouble codes will most likely appear with a P0829 code. It is always recommended to diagnose and repair trouble codes in the order in which they appear, as some may simply be a symptom of a larger problem.
Need help with a P0829 code?
YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.
This article originally appeared on YourMechanic.com as P0829 OBD-II Trouble Code: 5-6 Shift and was authored by Parker Hill.