Check engine light stays on

Good evening,

What is the exact code?

Low fuel pressure will cause several codes.

https://www.2carpros.com/articles/how-a-fuel-pump-works

Let's start at the beginning with the code.

Roy

P0171
P0174

Thank you.

Low fuel pressure will cause these codes.

As you stated, please check the fuel pressure and report back. If the pressure is off even 5 lbs. it will set this code as not enough fuel is being delivered to the fuel rail.

Also, check for any vacuum leaks.

Roy

Thank you Roy.
The pressure is off by 0.3 bar (3.5 as opposed to 3.8) which is 4.3 psi under the recommended.
However, the light suddenly went out!
I expect it will come back on any minute.
Sheru

Yes, it will definitely come back on.

Computers cannot fix themselves yet.

Roy

Doesn’t solve my problem.

I own a 2006 Hyundai Sonata V6. I have taken it to several dealerships because the check engine light had come on. During 3 of the inspections, they found Code P0456 and changed the following parts: Canister Valve, Purge Valve and Air Flow Meter. Is there something that they are missing? The light seems to be an ongoing issue and just came back on. Please, any info as to what the core issue could be, I'd appreciate it. I've got an appointment to take it, once again, back to the dealership for service. It would be nice to ask them to check for something specific.
Thanks much. John

Do you know if they have done a smoke test on it? It's a test that pumps smoke into the system which should be sealed. Wherever the smoke escapes is the leak. It shouldn't be a guessing game. The other thing to look for is the gas cap. If the vent on the cap is faulty it will set off the light. Find out about the smoke test though and post back any further info on their diagnostics if you can. Thanks

I do not think that they've performed a smoke test. It seems like they just hook the car up to their computer and whatever code their computer gives them, they work off of. I'll ask them to perform the smoke test and also ask about the gas cap vent. Hopefully, they'll be able to figure out what the real issue is. My next appointment is on Wednesday March 5th. I'll post an update after and let you know what the outcome is. Thanks again. John

They came back with the same code: P0456 and replaced the canister valve again. They said they did a smoke test and that a leak came from this part. They also checked the gas cap vent and said it was working properly. When my wife picked up the car today and started to drive the car from the dealership, the light came back on. There has got to be something that they're not seeing, doing, or checking. It's getting really fustrating. Please any additional help would be appreciated. Thanks.

I had my car detailed and specifically told the detail shop not to clean the engine out of fear that the moisture/water might get into the electrical system and cause problems. Well the idiots did and now my check engine light is on and the car runs very rough. It feels like it is going to stall. I took it to a mechanic friend of mine and he said that probably some moisture/water got into the plugs and wires. He told me to drive it for a few days and that it might dry out, otherwise replacing the the wires should take care of it. What do you think?

Most purge valves are electromechanical, meaning they require voltage to open a solenoid. Most of the time they are drop voltage 5vref. I'm beginning to wonder if maybe you have a short that is holding open the purge valve, or maybe the computer is getting a false signal from a monitoring sensor and commanding the solenoid to stay open. Since they have replaced the valve twice and it doesn't even make it home before it bums out again, the problem is not the canister valve. They have determined the symptom and addressed the system. They can identify the component, now they just need to find the cause. Something else is wrong and you need to have them look at the bigger picture. My suggestion would be to take it back and tell them you don't want it back until it is completely fixed. And make sure that they drive it for two complete drive cycles (complete warm up to complete cool down is one drive cycle).

Does the problem still exist? Is the check engine light still ON?

I've called hyundai customer service. They said that they would look at the car's history and call the dealership that's been working on my car. They said that they would work with the dealership to solve the problem. When I take the car back this Friday, I'll definitely tell them what you told me. Hopefully, they'll be able to figure out what the cause is and fix the problem this time. Thanks again for your help and I'll keep you updated as this gets resolved. John

Yes the check engine light turned off and the car is running like new again. Thanks

They finally found the real problem. When we first purchased the car, it needed a new fuel pump. They took two weeks to install it. While installing it, they did not set the O-Ring correctly on it, so the leak was from a gap in the O-Ring. It took several attempts and a call to customer affairs to get it right. We've had the car for more than a week now and the check engine light has remained off. Thanks for all your assistance with this. I'll definitely come back to this site if I need any more info or help. Thanks much, your help was appreciated. Sincerely, John.

OK.. Have a good day..

my check engine light is on just had o2 senser repalced and used engine put in 2 months ago with 29000 on it

Get the computer rescanned for code/s and get back with it if any present

location of check engine light censor

If the check engine light is coming on -you need to have the computer scanned for code/s this your starting point finding out what's going on.

I got a check engine light on my 2006 Hyundai Sonata LX. When I plugged in the diagnostic tool, the error messages I received were P2138 and P2106. Could you give me any information on these errors? Is it serious? Can I drive without having it fixed right away? How much would it cost to fix?

this is a bad gas pedal sender or piece of carpeting stuck under it, or a bad pcm(computer) or bad gas pedal switch. Your car is operating undr reduced power because of this. Costs vary by state and labor rates. I'd say you are looking at atleast $300 to fix this and check it out. If it's a pcm then it will be more money as it will need reprogramming.

I have a '03 Hyundai Sonata GLS. The check engine light came on and is reading P0150. I understand that this would be the oxygen sensor. Is there any way to tell which sensor it is so I can make sure I order the right one?

code numbers never identify bad parts, just a failed system.
i do not see a code 150. can you re check, the codes start at 151, 152.

most of the time, a o2 throws a code because it cannot do it job from something else. you need to get this confirmed before throwing parts at it.

what engine size do you have??

Roy

It is a 2.7L V6.

did you re verify the code number??

Roy

Yes, it still said P0150. I don't believe my reader can read the Hyundai specific codes, so the P0150 seems to be the Hyundai P0151 It also said- Bank 2/sensor 1

ok, that makes better sense.

you need to check the fuses as there is a heater in the o2 that may be bad. thats what the code indicates and yes, it may be bad.

bank 2 is the front of the motor. it is the sensor before the cat converter. it is called the upstream o2.

Roy

So I can try checking the fuses, or replace the O2 sensor which corresponds with the '03 Sonata GLS?

2 1/2 half years ago I experienced a sudden loss of power in the shifting of the gears in the transmission, like the codes that were displaying 1) Loss of Vacuum & 2) input/output speed sensor failure. Fortunately I had 2 months of warranty left. Supposedly...the transmission had to be overhauled, at there expense. What happened was a loud thud hit simultaniously when the check engine lite came on. Pay attention here closely...the transmission then hung up in 3rd gear. Would not shift into overdrive or downshift to either 2nd or 1st gear. You had to take off in 3rd gear. Also, operating temperature does have some effect on the shifting, like the next morning when I needed to use it the check engine light had cleared itself and...when I took off the gears shifted just fine, until about 5 minutes of operation then the incident would happen again...lock up in 3rd gear and check engine light came on again. Check engine light would always be on until the engine cooled down overnight and when you activated ignition the next morning check engine light would clear. After overhaul and 2 1/2 years later it does this again. I would like to know what really is going on here. What do I do? Do I have to get this transmission overhauled again? Please advise...thanks so much!

Hi purplus,

Thank you for the donation.

When the CEL shows, an error has been detected by the engine or transmission management system.

In your case, the problem shouod be a problem in the trans control system. When an error has been detected, the PCM would go into limp mode if it is a major fault. This would explain why it is stuck in 3rd gear.

Turning the engine off would allow the PCM to reset itself temporarily till it encounters the problem and then it would go into limp mode again.

Quite often problems like this are caused by sensor failure. If internal components are faulty, it could cause slipping in geasrs and this in turn would cause the PCM to go into limp mode as well.

To understand what is wrong, get a scan done at your local Autozone or parts outlets, they provide free scans. Let me know the exact Diagnostic Trouble Code and we shall see what needs to be done.

yes, i would check the fuses. if the sensor is bad and blew the fuse, you need to replace the fuse and the o2 or the code will return for no power to the o2 heater.

check the harness as well for broken wires or shorts.

Roy

ok...I went down to Auto Zone and they don't do engine scan tests anymore. So, I went down to a "AAA" approved facility/with ASE certified mechanics. I did extensive explaining to the mechanic. The codes that were bearing was PO732 & PO734. They changed both input and output speed sensors and cleared all codes. Drove it 3.9 miles and tranny jerked again and "engine light " illuminated again. At this moment I am going to drive it in 3rd gear back down to the shop again , ever so gently, to see what codes may be displaying now and will let you know in 24 hours what they were and then we can proceed. I have included Hyundai Consumer Affairs at 1-800-633-5151 on my situation. I have a reference number that is related to this issue. Reference #358-9799. Now after codes scanned today they are PO755 and PO760 which are Shift Solenoid B Malfunction and Shift Solenoid C Malfunction. Not good from what the mechanic advised. Which was take it to a Transmission Specialist. Needless to say I was out $320 yesterday and still have a screwed up vehicle. Just new codes now. Please advise. Thanks

Hi
Hyundai issued a TSB on your problem Reference # 03-04-006 Date May 01,2003.
Is says wiring harness maybe the fault checking resistence and any pin damage. If none found then replace solenoids normal warranty applys.
Hope this helps

My check engine light came on last night. This morning, AutoZone told me the code was P0302, but their machine did not say specifically for the Hyundai. However, every other vehicle type that came up stated that this particular code refers to "Cylinder 2 misfire detection." They suggested that I use a high Octane gasoline and add Fuel Injection Cleaner and that should fix it. Is this correct?

Hi lack4nothing,

Thank you for the donation.

OBD-II codes are universal, meaning all models would use the same code for the same diagnostic description, though causes and repair procedure might differ.

Here are the definition of the group of codes and what Autozone recommends might not solve the problem. Misfires can be due to various causes.

DTC P0301, DTC P0302, DTC P0303 & DTC P0304
Code Definition

• DTC P0301: Cylinder No. 1 Misfire Detected
• DTC P0302: Cylinder No. 2 Misfire Detected
• DTC P0303: Cylinder No. 3 Misfire Detected
• DTC P0304: Cylinder No. 4Misfire Detected

NOTE: Engine Control Module (ECM), can also be referred to as Powertrain Control Module (PCM).

NOTE: Testing individual components does not isolate shorts or opens. Perform all voltage tests using a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure. Use ohmmeter to isolate wiring harness shorts or opens.

System Description
With ignition switch at ON or START position, voltage is applied to ignition coil. Ignition coil consists of two coils and they are located on cylinder head spark plugs No. 1 and 2. High tension leads goes from cylinder ignition coil No. 1 to cylinder No. 4 and from cylinder ignition coil No. 2 to cylinder No 3. Ignition coil fires two spark plugs on every power stroke (cylinder under compression and cylinder on exhaust stroke). Coil number one fires cylinders 1 and 4. Coil number two fires cylinders 2 and 3. Powertrain Control Module (PCM) or Engine Control Module (ECM) provides a switching circuit to ground for energizing primary ignition coils. PCM/ECM uses crankshaft position sensor signal to time energizing of coil. When a primary ignition coil is energized and de-energized, secondary coil produces a high voltage spike across attached spark plugs. At same time, tach interface (part of ignition power transistor) provides PCM/ECM and Transaxle Control Module (TCM) with an RPM signal.

Failure Conditions
PCM/ECM detects misfire as change in angular acceleration of crankshaft. PCM/ECM will monitor for misfire when the following conditions are met:

• Engine has been running for at least 5 seconds.
• Engine speed is 500-6000 RPM.
• Engine coolant temperature is more than 14°F (-10°C).
• Intake air temperature is more than 14°F (-10°C).
• Vehicle is running free from sudden accelerations/decelerations such as gear change.

PCM/ECM sets DTCs P0301, P0302, P0303 or P0304 and turns MIL on when misfire has occurred more than 200 out of 1000 crankshaft revolutions.

If catalytic converter temperature is more than 1742°F (950°C), and misfire occurs more often than allowed in last 200 crankshaft revolutions, PCM/ECM determines severe misfire exists and will set DTCs P0301, P0302, P0303 or P0304 and cause MIL to blink.

Probable Causes

• Faulty Ignition system related part.
• Poor Crankshaft Position (CKP) sensor signal.
• Incorrect air/fuel ratio.
• Low compression pressure.
• Faulty Engine Coolant Temperature (ECT) sensor.
• Timing belt missing teeth.
• Faulty Fuel injector.
• Faulty EGR valve.
• Faulty PCM/ECM.

Test Procedure

1. Turn ignition off. Connect Hi-Scan Pro tool or equivalent to OBD-II Data Link Connector (DLC). Turn ignition on. Monitor and verify DTCs P0301, P0302, P0303 or P0304 are set. Go to next step. If DTCs P0201, P0202, P0203 or P0204 are set, do all repairs associated with those DTCs before continuing with this procedure.

2. Ensure vehicle is fueled with at least 87 octane fuel. If vehicle is fueled as specified, go to next step. If vehicle is not fueled as specified, refuel vehicle with 87 or higher octane. Go to step 5 .

3. Turn ignition off. Disconnect ignition coils 3-pin harness connector. Measure primary coil resistance between ignition coil connector terminal No. 1 and 2 (component side). Resistance should be approximately 1.3 ohms. Disconnect spark plug wires from ignition coils. Measure secondary coils resistance between ignition coils spark plug wires connectors No. 1 and 4, also between No. 2 and 3. Resistance should be between 10.3-13.9 k/ohms. If both resistances are as specified, go to next step. If any resistance is not as specified, replace ignition coil with known-good component. After repair, go to step 5 .

4. Perform an inspection of following systems and components:

• Spark plug and spark plug wires for cracks or damage.
• Fuel injectors clogging or wiring damage.
• Obstruction of Mass Air Flow (MAF) sensor.
• Vacuum hoses for damage or leaks.

If all components are in good operation condition, Verify than PCM/ECM connectors are secure. If connectors are okay, replace PCM/ECM with known-good component. Go to next step. If any component is faulty, repair or replace as necessary. Go to next step.

5. Return vehicle to original condition. Clear codes using Hi-Scan Pro tool or equivalent. Verify repairs by driving vehicle and monitoring for pending codes. If DTC is set during test drive, follow appropriate DTC test procedure.

© 2008 Mitchell Repair Information Co., LLC.

The check engine light came on, then took the car to a mechanic for a computer diagnostic.
Result was that I should get my coolant temperature sensor and the thermostat replaced.
The check engine didn't came back on ever since.
Should I still get it fixed now, or wait until the light comes back on ?

We would need the exact code number to give you any advice.

I cannot find the code on my receipt.
I guess what I am trying to find out is.
Just because the check engine light doesn't come on again does not mean there was not anything wrong with it. Or does it ?