P1700 Code: Complete DIY Repair Guide

The P1700 code is a diagnostic trouble code (DTC) that indicates a problem with the transmission control module (TCM) or the transmission itself. This code can affect both automatic and manual transmissions and is often associated with issues in the transmission’s electronic control system. When this code appears, it’s crucial to address it promptly to prevent potential transmission damage and ensure safe vehicle operation.

Faulty Transmission Control Module (TCM)

The Transmission Control Module is the brain of your vehicle’s transmission system. When it malfunctions, it can trigger the P1700 code.

Symptoms:

• Erratic shifting
• Transmission stuck in a single gear
• Check Engine Light illuminated

Technical explanation:
The TCM uses input from various sensors to control the transmission’s operation. When it fails, it can’t process this information correctly, leading to transmission issues.

Step-by-step diagnosis:

1. Connect an OBD-II scanner to read all transmission-related codes
2. Check for any software updates for the TCM
3. Inspect the TCM’s power and ground connections
4. Test the TCM’s input and output signals using a multimeter

Solution methods:

• Update TCM software if available
• Repair any damaged wiring or connections
• Replace the TCM if found faulty

Cost estimate: $300-$1000 for TCM replacement, depending on the vehicle make and model.

Warning: TCM replacement often requires professional programming to work correctly with your vehicle’s systems.

Wiring Issues and Damaged Connectors

Damaged or corroded wiring can disrupt communication between the TCM and other vehicle systems, triggering the P1700 code.

Symptoms:

• Intermittent transmission problems
• Multiple electrical issues

Technical explanation:
Proper electrical connections are crucial for the transmission system to function correctly. Damaged wiring can cause incorrect signals or loss of communication between components.

Step-by-step diagnosis:

1. Visually inspect all transmission-related wiring harnesses
2. Check for signs of corrosion, fraying, or damage
3. Use a multimeter to test continuity in suspect wires
4. Inspect all connectors for proper seating and pin condition

Solution methods:

• Repair or replace damaged wiring
• Clean corroded connectors
• Replace damaged connectors

Cost estimate: $50-$300, depending on the extent of the damage and labor costs.

Recommendation: Always use heat-shrink tubing and proper soldering techniques when repairing automotive wiring.

Low Transmission Fluid Level

Low transmission fluid can cause various transmission problems and trigger the P1700 code.

Symptoms:

• Slipping gears
• Overheating transmission
• Delayed or harsh shifting

Technical explanation:
Transmission fluid is essential for lubricating moving parts, cooling the transmission, and providing hydraulic pressure for gear changes. Low fluid levels can cause internal damage and erratic operation.

Step-by-step diagnosis:

1. Park the vehicle on a level surface
2. With the engine running and transmission in park, check the transmission fluid level
3. Inspect the fluid color and smell (burnt odor indicates issues)
4. Look for signs of leaks around the transmission

Solution methods:

• Add the correct type of transmission fluid to the proper level
• Repair any leaks found
• Perform a transmission fluid flush if the fluid is contaminated

Cost estimate: $50-$250 for fluid replacement, more if repairs are needed.

Warning: Always use the manufacturer-recommended transmission fluid to avoid compatibility issues.

Faulty Speed Sensors

Speed sensors provide crucial information to the TCM about the vehicle’s and transmission’s speed. When they fail, it can lead to the P1700 code.

Symptoms:

• Speedometer malfunction
• Erratic shifting
• Cruise control issues

Technical explanation:
There are typically two speed sensors in a transmission: the input shaft speed sensor and the output shaft speed sensor. These sensors use magnetic fields to generate signals that the TCM interprets as speed information.

Step-by-step diagnosis:

1. Use an OBD-II scanner to check for specific speed sensor codes
2. Locate the speed sensors on your transmission
3. Inspect the sensors and their wiring for damage
4. Test the sensors’ resistance with a multimeter

Solution methods:

• Clean the speed sensors if dirty
• Replace faulty speed sensors
• Repair or replace damaged wiring

Cost estimate: $100-$400 per sensor, including labor.

Recommendation: When replacing speed sensors, consider replacing both input and output sensors at the same time for consistent performance.

Damaged Transmission Range Sensor

The transmission range sensor, also known as the neutral safety switch, informs the TCM of the selected gear position. A malfunction can trigger the P1700 code.

Symptoms:

• Incorrect gear indication on the dashboard
• Vehicle starting in gears other than Park or Neutral
• Transmission not shifting properly

Technical explanation:
The range sensor uses a series of contacts to indicate the selected gear position to the TCM. When it fails, the TCM receives incorrect information about the transmission’s state.

Step-by-step diagnosis:

1. Check for additional transmission-related codes
2. Locate the transmission range sensor (usually on the side of the transmission)
3. Inspect the sensor and its wiring for visible damage
4. Test the sensor’s resistance at different gear positions using a multimeter

Solution methods:

• Adjust the transmission linkage if misaligned
• Clean the sensor contacts if corroded
• Replace the transmission range sensor if faulty

Cost estimate: $150-$400, including labor.

Warning: Improper adjustment of the transmission range sensor can lead to safety issues, such as the vehicle starting while in gear.

Conclusion

The P1700 code indicates a significant issue with your vehicle’s transmission system that requires prompt attention. While some causes, like low fluid levels, can be easily addressed by DIY mechanics, others may require professional diagnosis and repair. Always prioritize safety and consult a certified technician if you’re unsure about any repair procedures. Regular maintenance and prompt attention to warning signs can help prevent more severe transmission issues and costly repairs in the future.

Frequently Asked Questions About P1700

• Can I drive my car with the P1700 code?
  It’s not recommended to drive with this code active. The transmission may operate erratically or fail completely, potentially leaving you stranded or causing an accident.
• How urgent is it to fix the P1700 code?
  Very urgent. This code indicates a significant transmission issue that could lead to complete transmission failure if not addressed promptly.
• Will the P1700 code clear itself?
  No, the P1700 code will not clear itself. It requires diagnosis and repair of the underlying issue before it can be cleared.
• How much does it typically cost to fix a P1700 code?
  Costs can vary widely, from $100 for a simple fluid top-up to several thousand dollars for a complete transmission rebuild or replacement. An accurate estimate requires proper diagnosis.
• Can a P1700 code be caused by a bad battery?
  While unlikely, a weak battery could potentially cause electronic issues that might trigger this code. However, it’s more likely to be a transmission-specific problem.
• Is the P1700 code specific to certain car makes or models?
  No, the P1700 code can appear in various vehicle makes and models with electronic transmission control systems. However, the specific meaning may vary slightly between manufacturers.
• Can I clear the P1700 code without fixing the problem?
  While you can clear the code, it will likely return quickly if the underlying issue isn’t resolved. It’s crucial to fix the problem rather than just clearing the code.
• How long does it take to diagnose and repair a P1700 code?
  Diagnosis can take 1-2 hours, while repair time varies greatly depending on the cause. Simple fixes might take an hour, while major repairs could require several days.