What is an OBD2 code?

An OBD2 (On-Board Diagnostics) code is a diagnostic trouble code (DTC) generated by your vehicle's computer system when it detects a problem. These codes help identify specific issues with your vehicle's engine, transmission, emissions, or other systems.

How do I read OBD2 codes?

To read OBD2 codes, you'll need an OBD2 scanner. Plug it into your vehicle's OBD2 port (usually located under the dashboard), turn your key to the 'ON' position, and follow your scanner's instructions to retrieve the codes. Each code starts with a letter (P, B, C, or U) followed by four numbers.

What do the different types of OBD2 codes mean?

OBD2 codes are categorized by their first letter: P (Powertrain) for engine and transmission issues, B (Body) for interior systems like airbags, C (Chassis) for mechanical systems like brakes, and U (Network) for computer and module communication problems.

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Home » OBD2 Codes » P1702

Code P1702

Symptoms

• Check Engine Light is on

• Transmission may not shift properly

• Reduced fuel efficiency

Common Causes

• Faulty transmission control module

• Wiring issues in the transmission system

• Defective transmission sensors

Glossary

Transmission Control Module (TCM): A computer that controls the transmission's operation.

OBD-II Scanner: A device used to read diagnostic trouble codes from a vehicle's computer.

Related Codes

• P1701

• P1703

Laymans terms

This code means that the car's computer is using a backup plan because something isn't working right. It's like when you use a flashlight because the power went out.

Explanation

The P1702 code is triggered when the transmission control module (TCM) detects a fault and switches to a substitute function to maintain vehicle operation.

Technical description

P1702 indicates that the transmission control module has detected an issue with the transmission system and has engaged a substitute function to allow the vehicle to continue operating. This is a fail-safe mode to prevent damage to the transmission.

Diagnosis steps

• Use an OBD-II scanner to confirm the code

• Inspect the transmission wiring and connectors

• Test the transmission control module

Repair procedures

• Repair or replace damaged wiring

• Replace faulty transmission sensors

• Reprogram or replace the transmission control module

Tools required

• OBD-II scanner

• Multimeter

• Basic hand tools

Estimated repair cost

$200 - $1000

Difficulty level

Moderate

Commonly affected vehicles

• Ford Focus

• Mazda 3

• Honda Accord

Preventive measures

• Regular transmission maintenance

• Timely replacement of transmission fluid

• Routine inspection of transmission wiring

Error code type

Transmission Control System Issue

User experience recommendations

• Do not ignore the Check Engine Light

• Have a professional diagnose the issue

• Avoid driving the vehicle if shifting becomes erratic

Warranty information

Transmission issues may be covered under powertrain warranty, check with the manufacturer.

Historical data

The P1702 code has been associated with vehicles that have experienced transmission control module failures, particularly in older models.

Urgency level

Moderate – It is important to address this issue to prevent further transmission damage.

Legal and safety notice

Driving with a faulty transmission can be dangerous and may lead to further damage. Consult a professional mechanic.

Testing conditions

• Vehicle must be in operation

• Transmission must be shifting gears

Component location

The transmission control module is typically located near the transmission or under the vehicle's dashboard.

FAQs

Q: Can I drive my car with a P1702 code?
A: It's not recommended to drive for long distances as it may cause further damage to the transmission.

Q: How do I reset the P1702 code?
A: You can reset the code with an OBD-II scanner, but it's important to fix the underlying issue first.

Last updated: Jun 9, 2026 • Source: internal database

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