Check Engine, Service Engine Soon light, OBD II engine trouble codes

A: It could be something simple, like the fuel tank cap not being tight, but it's hard to know what causes the "Check Engine" light without knowing the code. I'd suggest to have your truck scanned somewhere and find out what the code is. It could be something like P0455. I know some auto parts stores can scan your computer for free. You actually can buy an OBD-II scan tool for as low as $30-$50 on eBay. Once you know the code, you can find out how to repair it.

A: This means that the OBD readiness monitor indicates that the vehicle's computer hasn't completed testing its systems: the Oxygen Sensor and its heater, EGR, EVAP system and the Catalytic Converter. To complete these tests the car needs to be driven, including some acceleration and deceleration, steady highway cruising and stop and go traffic. Sometimes it may takes just a half an hour of driving; sometimes it takes a couple of days. The EVAP and Catalytic Converter monitors are usually the last ones to complete. Once all emission monitors are complete, the OBD readiness monitor changes status as "Completed".

A: If the engine misfire is detected, the Check Engine light will come on to tell you there is something wrong with the engine and it needs to be looked at. The 'Check Emission Control' message on the multi-information display just repeats the same message in a different way. Both, the light and the message are caused by the same problem. All you need to do is scan for the trouble code and diagnose the problem according to the trouble code. If it's a misfire, you just need to find out why the engine misfires and have the problem fixed. Once the repair is completed, the Check Engine light will need to be reset with a scan tool. The Check Emission Control System message should go away once the Check Engine light is off. The 2011 vehicle should still be covered by the emission warranty, so the best place to take it is a local Honda dealer.

A: Yes, overfilling the gas tank can trigger the "check engine" light to come on. Modern cars are equipped with an Evaporative System that prevents gasoline vapors from escaping into the atmosphere. When we overfill the gas tank, the excess gasoline can enter the part of the Evaporative system called Charcoal Canister, which is designed to absorb gasoline vapors rather than raw fuel. This can cause some problems with the evaporative system that can trigger the check engine light.
Don't overfill the tank past the first click of the pump. Check your owner's manual.

A: The code P1400 reads "DPFE Sensor Voltage Low" (Ford, Mazda). Often it's caused by bad DPFE sensor or clogged EGR passages. Visit your local Ford dealer, they will be able to help you.

A: P1000 is not actually a trouble code. It just means that the Readiness code has not been set yet or in other words, the engine computer hasn't completed testing certain emission control components. If there is no other problems with the car emission system, the code P1000 will disappear after driving for some time (the drive cycle must include idling, stop and go traffic, acceleration and steady cruising).

A: The code P0456 means that the Evaporative system has a small leak. It could be a leak in one of the vacuum lines or a gas cap not sealing properly. A small leak is usually hard to find. Mechanics use a 'smoke machine' to find EVAP system leaks. Take it to a dealer or a mechanic that can 'smoke test' your EVAP system. The code P0107 means 'map sensor voltage too low'. You didn't tell which engine you have, but as far as I remember, the map sensor is located at the intake, close to the power steering fluid reservoir. A mechanic would need to check the 5V reference voltage and the ground at the sensor. Unless it's an intermittent problem, it should be fairly easy to diagnose. I did some research on this code on Dodge Caravan, and few sources mentioned a problem where the wiring going to the sensor melts causing some wires to short to ground.

A: The code P0456 - EVAP small leak, means that the Evaporative system has a small leak. It could be a leak in one of the vacuum lines or a gas cap not sealing properly. A small leak is usually hard to find. Mechanics use what is called a 'smoke machine' to find this type of leaks. It would be easier to take it to a mechanic that has a smoke machine to test for leak. The other two codes are relates to the throttle control and there is a wide range of problems that can cause the P2112 and P2106 codes. It could be a vacuum leak, a bad ECM or a problem with the wiring or connector at the throttle body, or even an indication of the limp mode. I'd take the truck to the Chrysler dealer; there might be a bulletin about reprogramming the ECM (engine computer) to repair these codes.

A: I don't have the access to the Honda service manual, but I did some research and here is what I found: Both codes are related to the Transmission Range Switch. This is the electric switch that shows which gear your transmission is currently in ( P R N D D1 D2). This switch is located on the transmission; at the place where the shifter cable connects to the transmission. I have a photo of similar Mazda transmission range switch to show you what it looks like. It could be a problem with the wiring, switch connector, cable adjustment or the switch itself is bad. Unless the problem is obvious, (e.g. corrosion in the connector), your mechanic will have to do some electrical diagnostic to find what exactly is wrong.

A: The code P0103 means mass air flow circuit high, the P1565 is the code for the throttle body. The P0303 means the cylinder number 3 misfires. Start with the code P1565. Check throttle body if it's clean and nothing jams it. There might be a carbon buildup that must be cleaned. Also check all the vacuum lines, they break easily on Passat. Check the air filter and the pre-filter screen for blockage. Once you clean the throttle body, try to find a shop that can perform throttle body adaptation with a Volkswagen-compatible scanner. The code P0103 could be caused by throttle body issues. The code P0303 might go away once you fix other issues. If not, it will need to be diagnosed separately.

A: You didn't tell what kind of a car is it, but if the computer detected a fault for the engine coolant temperature, this is the first thing to check if the mixture is rich. How it works: When the engine is started cold, it needs very rich mixture. Once the engine warms up, the air fuel mixture leans out. In newer cars, if the engine coolant temperature sensor is disconnected, the computer just calculates approximate temperature judging by the time the engine runs and some other parameters. In older cars, the computer wasn't that smart: if the engine coolant temperature sensor is disconnected, the engine computer thinks that the engine is cold and makes the mixture very rich. Even after some driving, as long as the computer doesn't see the engine temperature, it thinks it's cold.

A: The code P1491 in a Nissan Pathfinder means Vacuum cut valve bypass valve. In the 2003 Pathfinder this valve is installed at the back of the truck, close to the spare tire, above the axle. It looks like a small round plastic thing with four vacuum lines connected to it. There is a solenoid-type valve that is connected to the two middle vacuum line of the vacuum cut valve bypass valve. This whole assembly is a part of the EVAP system and is installed on the purge line between the EVAP canister and the fuel tank. Often it's that solenoid valve that goes bad. Normally it's closed, so no air goes through it. When the battery voltage is applied to the terminals of this solenoid, it clicks and opens the air flow. Of course, there could be few other possibilities like clogged vacuum lines, bad vent control valve, bad EVAP canister, etc. Often both this valves are replaced together.

A: The code P0420 stands for "Catalyst System Efficiency Below Threshold Bank 1", which means the catalytic converter is faulty. The catalytic converter is installed in the exhaust and is an important part of the vehicle emission control system. To monitor how well the catalytic converter does its job, there are two oxygen sensors installed in the exhaust - one before and one after the catalytic converter. The engine computer constantly compares the signals from both sensors. If the catalytic converter can no longer do its job, the engine computer sets the P0420 code.
There could be few other reasons for the code P0420 to set, but in most cases, the catalytic converter will need to be replaced. This could be costly - the part is expensive.
If the car is still under emission warranty, or if it has expired just recently, your local Subaru dealer could help. If it's no longer covered by the warranty, any garage can do the repair. There might be even cheaper aftermarket catalytic converters available, but their quality is not always as good as the original one - I'd recommend to use the original Subaru catalytic converter. Read more about the trouble code P0420