Skip the auto shop - Our mechanics make house calls

Q: What Do Transmission Error Codes Tell You?

asked by on

What do transmission error codes tell you?

Using transmission error codes is a necessary procedure for a transmission technician since automatic transmissions have been computer controlled for over 20 years. The transmissions currently in use are very different to diagnose and repair than transmissions from decades ago. For correct operation, transmissions rely on accurate electrical inputs from multiple sensors. A transmission control module (TCM) processes the inputs, “decides” what the correct action is for the current conditions, and sends out commands to actuators. The required training, electrical understanding, tooling, and diagnostic skills required of transmission technicians have all increased dramatically. Fortunately, the automatic transmission control systems are designed to be able to provide some clues to a technician about what “might” be faulty. These are the fault codes or error codes. A technician obtains them from the vehicle’s control module using a scan tool. Codes may indicate issues with the speed sensors, shift solenoids, pump pressures, valve body circuits, or slipping clutches. The fault can be the TCM itself, programming calibration, or electrical wiring, connections, or grounds for any of these. The scan tool and code doesn’t tell a technician what part to replace, but does provide direction to an experienced, trained technician in the diagnostic process.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!
  1. Home
  2. Questions
  3. What Do Transmission Error Codes Tell You?

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Sequaling noise on light acceleration when the engine is warm

You should have the serpentine belt and belt tensioner checked and replaced as a set if it is the cause of the squeal. This is the most common cause of squealing. If you would like, a certified technician from YourMechanic...

Q: Truck stuck in park

Be sure that you are fully depressing the brake pedal when shifting out of park as there is a parking pawl in the transmission that will prevent movement off the shifter workout first setting the brake compressed. If this does...

Q: If a code saying that my fuel sensor switch is not working properly goes unfixed, can it cause other issues later on?

Hi. The fuel pressure sensor's purpose is to relieve pressure in the fuel tank and the emissions system when it is needed to help control the pollutants the car puts out. The fuel pressure sensor being bad shouldn't affect the...

Related articles

Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...