Kenworth T680 Transmission: Fault Codes and Common Problems (2024)

The Kenworth T680 was introduced in 2013 as a replacement for both the narrow-body T660 and wide-body T700. This meant it had a huge gap to fill in the void left by its predecessors. However, the truck was certainly able to pull its own weight and rise from the pack with its aerodynamic design, PACCAR engine, and 12-speed automatic transmission.

The utilization of a 12-speed transmission provides the Kenworth T680 with a wide range of gear ratios that help enable its quicker shifting, and in turn, offer excellent fuel and driving efficiency overall plus better accelerations.

While the specs of the truck are definitely impressive on paper, there are certain problems with its transmission that you should watch out for though.

Most Common Fault Codes and Problems in the Kenworth T680

The PACCAR transmission system of the Kenworth T680 is generally superb in terms of performance and quality. However, it still had its share of problems along the way that led to several complaints and some recalls.

To ensure the long-term reliability of your Kenworth T680 truck, here are the most common fault codes relating to its transmission that you should watch out for:

1. Fault Code P0700: Transmission Control System Malfunction

The transmission control system of the Kenworth T680 truck is responsible for managing the shift points and torque converter lock-up of the automatic transmission. It monitors engine operation, vehicle speed, and other parameters to determine when to smoothly engage or disengage gears. When a code such as P0700 appears on the diagnostic readout, it means there is a problem with this system.

To diagnose the cause of the problem with P0700 in the Kenworth T680, technicians must first observe any symptoms associated with transmission control system malfunction.

Common indications include erratic shift points, delayed gear engagement, slipping between gears, changes in RPMs without corresponding acceleration or deceleration, and the illumination of the check engine light. After observing these symptoms, a technician can use specialized tools to confirm which parts are failing.

Once the faulty part is identified, replacing it is usually enough to resolve the issue. If the cause of P0700 appears to be an electrical problem, technicians may need to replace wiring or sensors that are not working properly. In some cases, multiple parts may need to be replaced to restore the normal operation of the transmission control system.

The common items that may need to be replaced include the valve body solenoids, shift actuators, and electronics plus the filters and gaskets associated with these components. In any case, proper diagnosis of the underlying problem should always come first so that unnecessary repairs can be avoided. By following proper troubleshooting procedures and using specialized tools for testing, the cause of P0700 in a Kenworth T680 can be found and fixed quickly.

2. P0750-P0770: Shift Solenoid Failure

The shift solenoid is an electromechanical valve that helps regulate fluid flow in a vehicle's transmission system. It is used to control the gear shifting, allowing the driver to change between different gears while driving. In particular, it is responsible for controlling when and how quickly the transmission shifts from one gear to another. This can be done manually or automatically depending on the make and model of the vehicle.

When diagnosing a fault code P0750-P0770 related to a shift solenoid failure in the Kenworth T680 truck, certain symptoms should be monitored for confirmation. These include delayed shifting, slipping, or jerking during gear changes, as well as difficulty getting into reverse or park. Additionally, a check engine light may be illuminated, indicating that there is an issue with the transmission.

To confirm what part is failing, it is important to use special tools such as an oscilloscope or a scanner. These will allow for measuring shift solenoid resistance and checking for electrical issues. It may also be necessary to turn off the engine, disconnect the harness from the shift solenoid, and measure the voltage between pins 1 and 2 of the solenoid connector while the vehicle is running.

If any of these tests indicate a problem with the shift solenoid, then possible solutions include replacing failed components such as gaskets, seals, and O-rings; cleaning out any debris clogging inlet or outlet screens; replacing the shift solenoid itself; and/or replacing the transmission oil filter. In addition, it may be necessary to inspect the wiring and connectors for any corrosion or damage.

Finally, depending on the severity of the problem, it may be beneficial to take further steps such as flushing out any old fluid from the system, refilling with new fresh fluid, and resetting all electronic controls for optimal performance.

When completing these tasks, it is important to use only parts that are OEM-certified and designed specifically for the Kenworth T680 truck to ensure that they will fit properly and perform correctly. Doing so will help prevent further issues down the line.

3. Fault Code P0218: Transmission Temperature has Exceeded

When the fault code P0218 is triggered in a Kenworth T680 truck, it indicates that the transmission temperature has exceeded its specified limits. To diagnose what is causing this issue, one needs to look at the symptoms associated with a temperature that is too high.

These may include delayed gear shifts when accelerating or decelerating, slippage throughout different gears, or even a burning smell.

To confirm which parts are failing, it is important to use specific tools like an OBD scan tool and an infrared thermometer. The first one can help identify any issues with vehicle systems as well as transmitters and electronic components. Meanwhile, the thermometer will provide readings of all fluid temperatures within the system and can easily pinpoint the exact component that is causing an issue.

Once the faulty part has been identified, it can be replaced with a new one. Possible solutions may include repairing or replacing the transmission fluid as well as any worn-out parts such as seals, gaskets, and filters.

In some cases, more serious issues like warped drums or broken bands may need to be addressed for the transmission temperature to return to normal levels. It is also important to make sure that all other components are installed correctly and securely so that damage or overheating does not occur again in the future.

Lastly, when attempting to diagnose and repair any problems related to transmission temperature exceeding its limits on a Kenworth T680 truck, it is essential to use the right tools and parts to get the job done correctly.

Failing to do so can result in further damage or even complete failure of the transmission system, leading to costly repairs and replacement costs. Taking the time to properly diagnose and remedy this issue is paramount for keeping a vehicle running smoothly and safely.

Quick Fix that You Can Try

By following the abovementioned steps, a driver or mechanic can ensure that any issues related to the transmission system of a Kenworth T680 truck are properly identified and fixed before major damage occurs. This will help keep vehicles operating at their best and save money on costly repairs down the line.

There are times, however, that the cause of your trouble may only lie in a simple glitch in the system of your auto. In this case, it may be easily remedied via a simple reset using a PC-based service tool. You can also do this manually using the following steps:

• Shift your truck to Neutral.
• Engage its parking brake.
• Turn off the engine.
• Start the truck by turning the key in the ignition.
• Turn it off after a second or two.
• Repeat steps 4 and 5 for six times but with at least a five-second interval between each restart. End the process with the engine on.
• Turn off the engine of your truck.

After these, try restarting your truck after a few seconds and drive it around while observing if the problem will recur. If the problems persist, better have your vehicle checked for possible transmission or electrical parts failure that could be indicated by any of the fault codes discussed previously or other reasons not mentioned here.

Conclusion

Fault codes in a truck such as the Kenworth T680 indicate specific problems within the vehicle's systems. From issues with the transmission to engine performance, these fault codes provide critical insight into what needs to be repaired or replaced. As such, it is important that anyone operating a truck like the Kenworth T680 take any fault codes seriously and address them promptly.

Ignoring fault codes can lead to breakdowns or even more extensive damage that could affect safety, reliability, and the overall cost of ownership. The earlier a fault code is identified and addressed, the better chances there are of quickly resolving an issue before it turns into something more serious.

Moreover, having knowledge of how different systems work and being able to interpret various faults helps ensure that only necessary repairs or replacements are made to the truck, leading to more cost-effective maintenance. Fault codes must be taken seriously and addressed promptly so that any issues can be resolved quickly and safely.

If you experience a fault code in your Kenworth T680, contact an experienced technician or garage as soon as possible, as they will have the expertise needed to accurately diagnose the issue and get your truck back on the road safely. Taking prompt action is key to avoiding breakdowns and minimizing costs associated with repairs or replacements.

It's also important to keep records of any fault codes encountered in order to identify potential patterns that could indicate a larger underlying problem that needs attention. By understanding what different fault codes mean and taking appropriate steps when one appears, you can ensure the reliability and safety of your Kenworth T680.