P0733 Code: Here's How to Solve It Fast

The P0733 diagnostic trouble code (DTC) is a powertrain code related to automatic transmission performance. It specifically indicates an issue with the third gear ratio in the transmission. When the vehicle's powertrain control module (PCM) detects that the actual gear ratio for third gear doesn't match the expected ratio, it triggers this code. Understanding and resolving the P0733 code is crucial for maintaining your vehicle's transmission health and overall performance.

P0733 Code Meaning	P0733 Code Common Causes
Incorrect third gear ratio detected	Low transmission fluid level
Transmission slippage in third gear	Worn or damaged transmission components
Discrepancy between input and output shaft speeds	Faulty shift solenoids
Transmission control module (TCM) detects ratio mismatch	Malfunctioning speed sensors
Potential internal transmission failure	Electrical issues in transmission circuitry

Low Transmission Fluid Level

One of the most common causes of the P0733 code is a low transmission fluid level. Insufficient fluid can lead to inadequate hydraulic pressure and lubrication, causing the transmission to slip or fail to engage properly in third gear.

Symptoms

• Delayed or harsh shifting
• Transmission slipping, especially in third gear
• Unusual noises from the transmission
• Burning smell from the transmission area

Technical Explanation

Automatic transmissions rely on hydraulic pressure to engage clutches and bands for each gear. When the fluid level is low, there may not be enough pressure to fully engage third gear, leading to slippage and an incorrect gear ratio.

Step-by-Step Diagnosis

1. Park the vehicle on a level surface and engage the parking brake.
2. With the engine running and at operating temperature, shift through all gears.
3. Return to park and locate the transmission dipstick.
4. Remove the dipstick, wipe it clean, reinsert it fully, and remove it again.
5. Check the fluid level against the "Full" and "Add" markings on the dipstick.
6. Inspect the fluid color and smell for signs of degradation or burning.

Solution

If the fluid level is low, add the appropriate type of transmission fluid to bring it to the correct level. Be careful not to overfill, as this can also cause issues.

Cost Estimate

• DIY fluid top-up: $20 - $50 for transmission fluid
• Professional service: $50 - $100 for fluid check and top-up

Warnings and Recommendations

Always use the transmission fluid specified in your vehicle's owner manual. Using the wrong type can cause severe damage to your transmission.

Worn or Damaged Transmission Components

Internal wear or damage to transmission components can cause the P0733 code. This may include worn clutch packs, damaged gear sets, or issues with the valve body.

Symptoms

• Slipping or harsh engagement in third gear
• Unusual noises when shifting into or out of third gear
• Inconsistent shifting behavior
• Transmission warning light on the dashboard

Technical Explanation

The transmission's internal components work together to provide the correct gear ratios. When these parts wear out or become damaged, they can cause slippage or incorrect gear engagement, leading to an improper gear ratio in third gear.

Step-by-Step Diagnosis

1. Connect an OBD-II scanner to retrieve all related codes and live data.
2. Perform a road test, paying close attention to third gear operation.
3. Monitor transmission temperature and pressure readings if available.
4. Conduct a transmission fluid pressure test to check for internal leaks.
5. Inspect the transmission pan for metal debris when changing the fluid.
6. If equipped, use the transmission's self-diagnostic mode for further testing.

Solution

Depending on the extent of wear or damage, solutions may range from replacing specific components to a full transmission rebuild or replacement.

Cost Estimate

• Clutch pack replacement: $500 - $1,500
• Valve body replacement: $400 - $800
• Full transmission rebuild: $1,500 - $3,500
• Transmission replacement: $2,000 - $4,000+

Warnings and Recommendations

Internal transmission work requires specialized tools and expertise. Unless you are an experienced mechanic, it's best to leave this to professionals to avoid causing further damage.

Faulty Shift Solenoids

Shift solenoids control the flow of transmission fluid to engage different gears. A faulty shift solenoid can cause incorrect gear engagement, leading to the P0733 code.

Symptoms

• Delayed or harsh shifting into third gear
• Transmission stuck in a particular gear
• Erratic shifting behavior
• Check engine light or transmission warning light illuminated

Technical Explanation

Shift solenoids are electrically controlled valves that direct transmission fluid to the appropriate clutch packs or bands. When a solenoid fails, it may not open or close properly, leading to incorrect fluid pressure and gear engagement issues.

Step-by-Step Diagnosis

1. Use an OBD-II scanner to check for additional transmission-related codes.
2. Review the vehicle's transmission control module (TCM) data for solenoid operation.
3. Perform electrical tests on the solenoid circuits for shorts or open circuits.
4. Use a multimeter to check the resistance of the shift solenoids.
5. If possible, remove and inspect the valve body for stuck or damaged solenoids.
6. Conduct a hydraulic pressure test to verify solenoid operation.

Solution

Replace the faulty shift solenoid or, in some cases, the entire solenoid pack or valve body assembly.

Cost Estimate

• Individual shift solenoid replacement: $150 - $400
• Solenoid pack replacement: $250 - $600
• Valve body replacement: $400 - $800

Warnings and Recommendations

Ensure you identify the correct faulty solenoid before replacement. Some vehicles may require recalibration of the transmission control module after solenoid replacement.

Malfunctioning Speed Sensors

The transmission uses input and output speed sensors to determine gear ratios. A faulty speed sensor can provide incorrect data, triggering the P0733 code.

Symptoms

• Erratic speedometer readings
• Inconsistent or harsh shifting
• Transmission slipping or not engaging properly
• Traction control or ABS warning lights may also be illuminated

Technical Explanation

Speed sensors measure the rotational speed of various transmission components. The PCM uses this information to calculate gear ratios and control shifting. If a sensor provides inaccurate data, the PCM may incorrectly determine that the third gear ratio is incorrect.

Step-by-Step Diagnosis

1. Use an OBD-II scanner to check for additional speed sensor-related codes.
2. Review the live data stream for inconsistencies in speed sensor readings.
3. Inspect the wiring and connectors for the input and output speed sensors.
4. Use a multimeter to test the resistance and voltage output of the sensors.
5. Compare the sensor readings to known good values for your specific vehicle model.
6. If possible, use an oscilloscope to observe the sensor waveforms.

Solution

Replace the faulty speed sensor. In some cases, cleaning the sensor or repairing wiring may resolve the issue.

Cost Estimate

• Speed sensor replacement: $100 - $300
• Wiring repair: $50 - $200

Warnings and Recommendations

Always use high-quality replacement sensors, preferably OEM parts, to ensure proper functionality and avoid recurring issues.

Electrical Issues in Transmission Circuitry

Electrical problems such as short circuits, open circuits, or corroded connections can cause erratic transmission behavior and trigger the P0733 code.

Symptoms

• Intermittent transmission issues
• Multiple transmission-related codes
• Erratic shifting or complete transmission failure
• Electrical system warning lights on the dashboard

Technical Explanation

The transmission control system relies on a complex network of wires, connectors, and modules. Any disruption in this electrical system can lead to incorrect signals being sent or received, potentially causing the PCM to detect an incorrect third gear ratio.

Step-by-Step Diagnosis

1. Visually inspect all accessible transmission wiring and connectors.
2. Check for signs of corrosion, damage, or loose connections.
3. Use a multimeter to test continuity in transmission-related circuits.
4. Perform voltage drop tests across suspicious connections.
5. Check ground connections for the transmission control module and sensors.
6. Use a scan tool to monitor live data for any erratic readings or communication errors.

Solution

Repair or replace damaged wiring, clean corroded connections, and ensure proper ground connections. In some cases, replacing entire wiring harnesses may be necessary.

Cost Estimate

• Wiring repair: $100 - $500
• Wiring harness replacement: $200 - $1,000+
• Connector replacement: $50 - $200

Warnings and Recommendations

Electrical issues can be complex and intermittent. Take care when working with vehicle electrical systems, and always disconnect the battery before performing repairs.

In conclusion, the P0733 code indicates a problem with the third gear ratio in your vehicle's transmission. While it can be caused by various issues ranging from low fluid levels to internal transmission damage, proper diagnosis is crucial for effective repair. Always start with the simplest and most common causes, such as checking fluid levels and electrical connections, before moving on to more complex issues. If you're unsure about any step in the diagnostic or repair process, it's best to consult with a professional mechanic who has experience with transmission issues. Remember, addressing transmission problems promptly can prevent more extensive and costly damage in the long run.

Frequently Asked Questions About P0733

• Can I drive my car with the P0733 code?
  While you may be able to drive short distances, it's not recommended to continue driving with this code present. The transmission issue could worsen, potentially leading to more expensive repairs or complete transmission failure.
• How urgent is it to address the P0733 code?
  The P0733 code should be addressed as soon as possible. Continuing to drive with an incorrect gear ratio can cause accelerated wear on transmission components and potentially lead to more severe issues.
• Will the P0733 code clear itself?
  The code may clear itself temporarily if the issue resolves, but it will likely return if the underlying problem isn't fixed. Proper diagnosis and repair are necessary for a permanent solution.
• Can a transmission flush fix the P0733 code?
  In some cases, if the code is caused by dirty or low transmission fluid, a flush and fluid replacement might resolve the issue. However, this won't fix mechanical or electrical problems causing the code.
• How much does it typically cost to fix a P0733 code?
  Costs can vary widely depending on the cause, ranging from about $100 for a fluid change to several thousand dollars for a transmission rebuild. An accurate estimate requires proper diagnosis of the specific issue.
• Can a bad battery cause the P0733 code?
  While unlikely, a weak battery can cause various electrical issues that might indirectly lead to transmission problems. However, it's not a common cause of the P0733 code specifically.
• Is the P0733 code specific to certain vehicle makes or models?
  The P0733 code can occur in any vehicle with an automatic transmission, regardless of make or model. However, some vehicles may be more prone to specific issues that trigger this code.
• Can I reset the P0733 code without fixing the problem?
  While you can clear the code using an OBD-II scanner, it will likely return if the underlying issue isn't resolved. Clearing codes without fixing the problem is not recommended and may be illegal in some areas.