P0700 Code: Transmission Control System (MIL Request)

If your vehicle has set a P0700 code, it may have an issue with the transmission. This guide explains what a P0700 means and lists some possible causes and symptoms. We also provide you with some practical diagnostic steps and repair options.

What Does Code P0700 Mean?

P0700 is a diagnostic trouble code (DTC) that is stored in vehicles with automatic transmissions and indicates an error from the transmission control system. When the transmission control module (TCM) compares all the transmission sensor inputs for rationality and detects an error, it signals the engine control module (ECM), which in turn stores the code and triggers the check engine light.

As a generic DTC, code P0700 is a broad indicator of a transmission problem and does not pinpoint the exact cause. It also often appears with other transmission or engine codes. This is vaguely similar to the P0300 code, which indicates a misfire but doesn’t identify the cylinder.

What Causes Code P0700?

There are several reasons why a vehicle might register a P0700 code. In many cases, it’s triggered by low or dirty transmission fluid. It might also be due to issues with the transmission sensors or wiring. Another possibility is that the TCM itself could be malfunctioning, causing the code to appear.

A P0700 fault code could also indicate a serious problem with the vehicle’s transmission components, such as the transmission solenoid, valve body, or clutch. In such cases, the damage to these components might be severe enough to affect the readings of the control sensors and trigger the code.

• Low or contaminated transmission fluid
• Sensor malfunction
• Wiring problems
• Control module malfunction

Low or Contaminated Transmission Fluid

Low fluid levels can cause moving parts to overheat and affect sensor readings, while dirty or contaminated fluid can hinder proper fluid flow.

Sensor Malfunction

If the transmission’s speed, pressure, and temperature sensors start to fail, they might send zero or incorrect signals to the TCM.

Wiring Problems

Worn or damaged wiring harnesses, connectors, and ground connections can disrupt communication between the sensors and the TCM.

Control Module Malfunction

Sometimes, the TCM itself may fail and generate inaccurate readings that can trigger the P0700 code.

What Are the Symptoms of Code P0700?

In addition to an illuminated check engine light, other reported symptoms of code P0700 include engine stalling and rattling noises coming from the transmission.

• Check engine light turns on
• Limp mode
• Shifting problems
• Higher fuel consumption

Check Engine Light Turns On

Also known as the malfunction indicator lamp, the check engine light automatically turns on once a DTC is recorded. In some vehicles, a separate transmission warning light may light up instead.

Limp Mode

Some vehicles may also go into a fail-safe mode or “limp mode,” a safety measure that helps prevent further damage to critical vehicle components at the expense of reduced power and non-critical functions disabled.

Shifting Problems

You may experience jerky, delayed, or abrupt shifts when changing gears. The gears may also start to slip, causing the vehicle to lose power when accelerating or going uphill.

Higher Fuel Consumption

The vehicle may consume more fuel due to inefficient gear switches and erratic shifting patterns.

How to Diagnose Code P0700

Diagnosing the cause of any trouble code can be a complex task, but it’s possible if you have the time and equipment. Among the general steps you can expect to take are:

Retrieve and Analyze the Codes

Use an OBD-II scan tool to retrieve stored codes and freeze frame data from the ECM, which can provide more information on what caused the code P0700 to appear.

Check the Transmission Fluid

Check if the transmission fluid is still at the manufacturer’s recommended level. Note the fluid’s color and odor: if it is dark and gives off a burnt smell, it needs to be changed.

Inspect Wiring and Connectors

Examine the wiring harness and connectors for signs of damage, corrosion, or loose contacts.

Inspect the Sensors

Temperature, speed, and pressure sensors may also be checked for signs of damage or any other visible issues.

Check the TCM

In some cases, the TCM may need to be taken for advanced diagnostics to check if it is causing the code to appear.

How to Fix Code P0700

Obviously, the way to get rid of a code P0700 on your vehicle depends on what’s causing it. Once you’ve pinpointed the underlying cause, here are the common fixes you may want to attempt:

Refill or Change Transmission Fluid

Add more transmission fluid if fluid levels are low. If the transmission appears dirty or contaminated, drain it out completely and change both the fluid and the filter.

Repair or Replace Wiring

Dirt or minor corrosion on contact points can usually be cleaned with contact cleaner, but severely damaged, worn, or corroded wires and connectors must be replaced.

Replace Sensors

Any faulty sensors will also have to be replaced. Make sure the replacement sensor is an OE-compatible unit to prevent the code from returning.

Repair or Replace the TCM

The TCM may have to be updated or reprogrammed in case of a glitch or outdated software. However, if it has suffered hardware failure, it will have to be replaced.

Clear the Code

Use an OBD-II scan tool to clear the code P0700 and other remaining codes stored in the onboard computer. The vehicle must also undergo a test drive to check if any codes or symptoms return.

Other Codes Related to P0700

As a generic code, a P0700 code may appear with other more specific error codes. Some of the more common codes related to P0700 are:

P0701

This error code indicates an internal problem with the transmission’s operations, such as how it shifts gears.

P0702

This code means an electrical problem has been detected within the transmission control system.

P0713

This code appears when the ECM has detected an abnormal signal from the transmission’s temperature sensor.