Skip the auto shop - Our mechanics make house calls

Q: Check Engine light on

asked by on

I brought my car for inspection and it failed due to the check engine light. It's showing a P0740 and P1456 codes. I went to my regular mechanic and said that I need to replace my transmission! About a month ago, I was there for an oil change and a transmission fluid replaced. My maintenance required went off but then the check engine light went on? I'm asking for a second opinion. Thanks!

My car has 218183 miles.
My car has an automatic transmission.

Fault code P0740 has to to with the evaporative system. It can be as simple as a loose fitting or sealing gas cap. It can also be more involved to include the purge valve and/or bypass solenoid. When you add fuel to the tank, the fumes need to be vented or the tank will not fill. The fumes are routed through valves and hoses into the charcoal canister. They are stored there until the engine is running. Then the system sends the fumes forward to the engine to be burned away. If this system is not tight (pressurized), then this fault can be set. Code P1456 has to do with torque converter lock-up. The torque converter is what connects the engine to the transmission to transmit power to the wheels. At certain speeds, the torque converter will "lock up" - create a 1 to 1 connection with the engine and transmission for maximum efficiency. If this lock up is not occurring, this code will be set. It may very well require a transmission replacement. Replacing the transmission fluid neither caused this not would have prevented it from happening. You can try replacing the gas cap with a genuine replacement but I would have a local transmission specialist inspect the transmission to determine if there is an alternative to replacing it.

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

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: dealership quoted $700 for struts on a 07 honda pilot ex-l. they called back and said they were completely shot and need a total

Hi there. It is quite possible that you have damage to strut mounts and support components within the system that is causing the increase in repairs. When an initial inspection is completed, it's typically an estimate based on damage they...

Q: do you know how long it would take to replace an oxygen sensor in a 2005 nissan murano?

Hello. We'll be happy to assist you. The labor time will depend on which oxygen sensor you need replaced. There are four different oxygen sensors on your vehicle. There are two upstream and two downstream oxygen sensors. We will have...

Q: What are the symptoms of VSA light on in 2009 Honda Accord EXL 2.4 liter?

Hi There, The VSA light indicates that something may be wrong with your Vehicle Stability Assist (VSA) system, otherwise known as your traction control system. The traction control system uses wheel speed sensors at each of the wheels, which monitor...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...