Transmission Gear 4 Incorrect Ratio
The P0734 code indicates that the powertrain control module (PCM) has detected an incorrect gear ratio when the transmission is commanded to shift into 4th gear. This typically means the transmission is slipping or not engaging properly, often due to internal mechanical issues, low fluid, or solenoid problems.
1. Symptoms You Will Notice
- Check Engine Light illuminated
- Harsh or delayed shifting
- Transmission slipping out of gear
- Reduced fuel economy
- Vehicle may go into limp mode
2. Most Common Causes
- Low or degraded transmission fluid level/condition
- Clogged transmission filter
- Faulty or stuck shift solenoid
- Worn or damaged 4th gear clutch pack
- Excessive torque converter slippage
- Faulty input or output speed sensor
- Internal mechanical transmission problems (bands, planetary gears, thrust washers)
- Transmission control module (TCM) with outdated or corrupted software
3. Step-by-Step Diagnosis
Step 1: Check transmission fluid level and condition; top off or replace if necessary.
Step 2: Scan for additional codes and perform a transmission system test.
Step 3: Inspect wiring and connectors to the transmission solenoids and TCM.
Step 4: Test shift solenoids and valve body operation.
Step 5: Perform a pressure test to check for internal leaks or worn components.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as it can cause further transmission damage. Limited driving to a repair shop is acceptable.
How much does it cost to fix?▼
Costs vary from $150 for a fluid change or solenoid replacement to $500+ for internal repairs or transmission rebuild.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.