How to Fix the P0700 DTC Code on Duramax (Expert Guidance)

If you’re a seasoned rider of Duramax diesel trucks, we bet you’ve come across quite a few Diagnostic Trouble Codes (DTCs). Although they can be a big pain out of the blue, they still play an important role in modern driving, helping to identify the problem with your car and the solution.

Among the most commonly found OBD-II codes on Duramax trucks is P0700, which indicates a transmission control system error. Various factors can trigger it, but it most frequently occurs due to low or contaminated transmission fluid.

The P0380 code can be frustrating, but don’t worry. This troubleshooting guide is here to help. We’ll go over the details of the P0700 error code, why it occurs, possible fixes, and associated costs.

How to Fix the P0700 DTC Code on Duramax

What Does P0700 Code Mean On Duramax?

As mentioned above, the P0868 code on Duramax Diesel trucks means the vehicle has a system error in its transmission control unit. Here’s a breakdown of what the code has to do with this problem.

  • P = Powertrain, the system of components that propels your car forward (In our case, this is the transmission).
  • 0 = a generic number derived from the SAE standard
  • 7 = Transmission
  • 00 = Specific fault index (In our case, this denotes a malfunctioning control system)

When this malfunction occurs, the Check Engine Light comes on, and the vehicle triggers itself to set the failsafe mode. As soon as it is set, the failsafe mode will remain in effect until you repair it or restore the system to function normally.

How Serious Is P0700 Code On Duramax?

The P0700 code can indicate severe and more extensive problems with the transmission or an imminent transmission failure. Additionally, the code on Duramax can cause drivability issues. The transmission may slip or hesitate when shifting gears, and in some cases, the vehicle may not move at all.

What Are The Symptoms Of The P0700 Code On Duramax?

A sudden dip in engine performance may signify something wrong with your transmission control module. If you notice this and then the Check Engine Light comes on, there’s a good chance you’ll soon have to deal with code P0700. Other symptoms of the P0700 error code may include:

  • Hesitation when shifting gears
  • Stalling or trouble starting
  • A burning smell coming from the engine bay
  • A sudden drop in fuel economy
  • The truck can only run on two gears

What Causes P0700 Code On Duramax?

A few different things can cause the P0700 code, but it’s due to low or contaminated transmission fluid in most cases. If the fluid is too low, the truck may not have enough pressure to shift gears properly. Other possible causes include:

  • Faulty wiring or connectors
  • A failed transmission control module
  • A bad shift solenoid
  • A faulty transmission valve body
  • Short circuits or open circuits in the transmission

How To Fix P0700 Code On Duramax?

If you notice any of the symptoms mentioned above, it’s time for a trip to the mechanic. They’ll use an OBD-II scanner to check for the P0700 code and any other trouble codes that may be present before taking further steps.

However, if you’re an experienced troubleshooter with the necessary tools and know-how about automatic transmissions, you can try fixing the problem by following the steps below.

Step-1: Retrieve Codes from TCM

The first step is to retrieve codes from the transmission control module (TCM) and obtain the freeze frame data. This will help you pinpoint the problem area to fix it.

You’ll need to connect an OBD-II scanner to the truck’s diagnostic port and then turn the ignition on (don’t start the engine). Once the scanner is powered on, select the “Read Codes” function and then choose “Transmission.”

The codes will be displayed on the screen along with their definitions. Write them down so that you can reference them later.

Step-2:  Check the Transmission Fluid Level and Condition

Next, check the transmission fluid level and condition. If it looks burnt or has particles in it, you’ll need to replace it. Make sure to also check for leaks while you’re at it.

If the fluid looks clean but low, you’ll need to add more. You can do this by removing the dipstick, adding fluid until it reaches the “full” line, and then reinserting the dipstick.

Step-3: Check for Wiring or Connector Problems

Once you have the codes, the next step is to check for wiring or connector problems. This is usually the case if you get a code that refers to an electrical issue.

Start by checking all the wiring and connectors going to and from the TCM. Ensure they’re all plugged in properly, and there are no loose wires. If you find any damaged or corroded wiring, replace it with a new wire of the same gauge.

Step-4: Check for a Failed Shift Solenoid

If you have a code that refers to a shift solenoid, the next step is to check for a failed shift solenoid. Remove the transmission pan and then check the electrical connector going to the shift solenoid. When the shift solenoid isn’t receiving power, the problem is most likely a bad shift solenoid. You’ll need to replace it with a new one.

Step-5: Check for a Faulty Transmission Valve Body

When you receive a code indicating a faulty transmission valve body, the next step is to check for a faulty transmission valve body. You’ll need to remove the transmission pan and then visually inspect the valve body for any damage. New valves will need to be installed if any valves are damaged.

If everything looks good, the problem may be with the TCM itself. In this case, you’ll need to replace the entire module.

How Much Does It Cost To Fix Duramax P0700 Code?

Most shops charge per hour for diagnoses of your truck. The average cost is $80 to $120 per hour.

If a transmission fluid flush is recommended, the price will be within the $200 to $300 range. You should also expect to pay for new transmission fluid, which typically costs around $20 per quart.

Replacing a shift solenoid will cost you anywhere from $100 to $200 while replacing a transmission valve body will set you back by $500 to $800. And if you need to replace the TCM itself, you’re looking at a bill of around $1,000-$1500.

Keep in mind that these are just estimates. The actual cost may vary depending on your Duramax model and the severity of the problem. Also, if your car is still under warranty, then the repair may be covered.

Can You Drive Your Duramax With Code P0700?

No, it’s not recommended to drive your car with this code. Driving with this code can cause further damage to your transmission and even the whole engine, which will end up costing you more money in the long run.

But on top of that, it’ll risk your safety and the safety of others on the road. You should stop immediately and have it towed to a nearby shop for diagnosis and repair.


When you receive a P0700 trouble code and must address a TCM issue, you might want to try the suggested fixes above if you possess the relevant expertise.

But given how ominous transmission troubles can be, it is advisable to have the truck serviced by a mechanic or dealer right away. And if you have to get a repair done, remember to have the vehicle inspected beforehand.

Chances are, replacing an additional part will fix some other problem and help you avoid another trip back. Getting back on the road will be easier and much safer that way.

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