The diagnostic trouble code (DTC) P0733 indicates an "Incorrect 3rd Gear Ratio" detected by your vehicle's Powertrain Control Module (PCM). This code signifies that the transmission is not achieving the expected gear ratio when in third gear. This can lead to poor performance, transmission damage, and potentially dangerous driving conditions. Understanding the causes, symptoms, and diagnostic procedures for P0733 is crucial for effective troubleshooting and repair.
| Category | Description | Possible Causes |
|---|---|---|
| Symptoms | Noticeable indicators of a P0733 code. | Check Engine Light: Illuminated on the dashboard. Transmission Slipping: Especially noticeable in 3rd gear. Harsh Shifting: Rough or jerky transitions between gears. Reduced Fuel Economy: The engine may work harder to compensate for the incorrect gear ratio. Limp Mode: The transmission may enter a limited-function mode to protect itself. Complete Loss of 3rd Gear: The vehicle may not shift into 3rd gear at all. |
| Possible Causes | Potential mechanical or electrical issues leading to the P0733 code. | Low Transmission Fluid: Insufficient fluid level. Dirty or Contaminated Transmission Fluid: Debris and contaminants affecting performance. Faulty Shift Solenoid: Malfunctioning solenoid responsible for controlling fluid flow to 3rd gear. Damaged Gears: Worn, chipped, or broken gears within the transmission. Worn Clutch Packs: Reduced friction in the clutch packs responsible for engaging 3rd gear. Internal Transmission Damage: More severe mechanical failures inside the transmission. Faulty Transmission Control Module (TCM): Rare, but a malfunctioning TCM can cause incorrect signals. Wiring Issues: Damaged, corroded, or loose wiring to the shift solenoids or TCM. Faulty Speed Sensors: Input and output speed sensors providing incorrect data to the PCM. Valve Body Issues: Malfunctioning valves within the valve body impacting fluid pressure and flow. |
| Diagnostic Steps | Procedures to identify the root cause of the P0733 code. | Check Transmission Fluid Level and Condition: Inspect the fluid level and look for signs of contamination. Scan for Diagnostic Trouble Codes: Use an OBD-II scanner to read any stored codes. Inspect Wiring and Connectors: Check for damage, corrosion, or loose connections to the solenoids and TCM. Test Shift Solenoids: Use a multimeter to test the resistance of the shift solenoids. Monitor Transmission Data: Use a scan tool to monitor real-time data from the transmission, including gear ratios, speed sensor readings, and solenoid activation. Perform a Transmission Flush: If the fluid is dirty, a flush may help to remove contaminants. Internal Transmission Inspection: If other tests are inconclusive, an internal inspection of the transmission may be necessary. Check Speed Sensors: Verify the proper function of the input and output speed sensors. * Valve Body Inspection: Examine the valve body for worn or sticking valves. |
Detailed Explanations
Symptoms
The symptoms of a P0733 code can vary depending on the severity of the underlying problem. The most common symptom is the illumination of the check engine light on your dashboard, indicating that the PCM has detected a fault. You may also experience transmission slipping, particularly when attempting to shift into or operate in 3rd gear. This slipping can feel like the engine is revving without a corresponding increase in vehicle speed. Harsh shifting between gears, especially when transitioning to or from 3rd gear, is another common symptom. A reduction in fuel economy can occur as the engine works harder to compensate for the incorrect gear ratio. In some cases, the transmission may enter limp mode, which limits the vehicle's speed and gear selection to protect the transmission from further damage. In the most severe cases, you may experience a complete loss of 3rd gear, meaning the vehicle simply won't shift into that gear.
Possible Causes
Several factors can contribute to a P0733 code. Low transmission fluid can cause insufficient lubrication and pressure, leading to slipping and incorrect gear ratios. Dirty or contaminated transmission fluid can also impede proper operation by clogging valve bodies and interfering with solenoid function. A faulty shift solenoid responsible for controlling fluid flow to 3rd gear can prevent the gear from engaging correctly. Damaged gears within the transmission, such as worn, chipped, or broken gears, can directly cause an incorrect gear ratio. Similarly, worn clutch packs responsible for engaging 3rd gear can reduce friction and cause slipping. Internal transmission damage, such as broken shafts or damaged bearings, can also lead to a P0733 code. While less common, a faulty Transmission Control Module (TCM) can send incorrect signals to the transmission, resulting in improper gear selection. Wiring issues, such as damaged, corroded, or loose wiring to the shift solenoids or TCM, can also disrupt communication and cause problems. Faulty speed sensors, specifically the input and output speed sensors, can provide inaccurate data to the PCM, leading to an incorrect gear ratio calculation. Finally, valve body issues, such as malfunctioning valves within the valve body, can impact fluid pressure and flow, affecting gear engagement.
Diagnostic Steps
Diagnosing a P0733 code requires a systematic approach. Start by checking the transmission fluid level and condition. Ensure the fluid is at the correct level and look for signs of contamination, such as a dark color or burnt smell. Next, scan for diagnostic trouble codes using an OBD-II scanner. This will confirm the P0733 code and reveal any other related codes that may provide additional clues. Inspect the wiring and connectors to the shift solenoids and TCM for damage, corrosion, or loose connections. Test the shift solenoids using a multimeter to check their resistance. This can help determine if a solenoid is faulty. Monitor transmission data using a scan tool to observe real-time information, including gear ratios, speed sensor readings, and solenoid activation. This can help pinpoint the source of the problem. If the fluid is dirty, perform a transmission flush to remove contaminants. If other tests are inconclusive, an internal transmission inspection may be necessary to identify any mechanical damage. Check the speed sensors to ensure they are functioning correctly and providing accurate data to the PCM. Finally, inspect the valve body for worn or sticking valves that may be affecting fluid pressure and flow. A pressure test may be needed to properly evaluate the valve body.
Frequently Asked Questions
What does the P0733 code mean? The P0733 code indicates that the vehicle's computer has detected an incorrect gear ratio while the transmission is in 3rd gear. This means the input and output speeds of the transmission are not matching the expected ratio for 3rd gear.
Can I drive my car with a P0733 code? Driving with a P0733 code is not recommended, as it can cause further damage to the transmission. It's best to have the issue diagnosed and repaired as soon as possible.
How do I fix a P0733 code? Fixing a P0733 code involves diagnosing the underlying cause and addressing it, which may include replacing faulty solenoids, repairing wiring, or rebuilding the transmission. Professional diagnosis and repair are often required.
Is low transmission fluid the only cause of P0733? No, while low transmission fluid can cause P0733, other causes include faulty solenoids, damaged gears, worn clutch packs, and internal transmission damage. A proper diagnosis is needed to determine the specific cause.
How much does it cost to fix P0733? The cost to fix P0733 can vary widely depending on the underlying cause and the extent of the damage, ranging from a few hundred dollars for a simple repair to several thousand dollars for a transmission rebuild or replacement.
Conclusion
The P0733 code signals a critical issue with your vehicle's transmission, specifically an incorrect gear ratio in 3rd gear. Prompt and accurate diagnosis is crucial to prevent further damage and ensure safe operation. It is highly recommended to consult a qualified mechanic for diagnosis and repair.