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Can't Get O2Heater and Cat Converter Tests to Set... Inspection almost up!

Please help!
2004 Hyundai Sonata GLS 2.7L V6 153K Miles.
Had a misfire back in October (cylinder 3)… took it to a local garage and they put new double platinum NGK plugs and wires in it (and did some other stuff)… Put over 1K miles on the car and all of the other diagnostics set except for these 2… No Check Engine Light, No Error Codes (I have my own OBDII basic reader and I’ve been checking it like every day)… I reset the diagnostics using the scanner and things went back to the same state with the diagnostics (02 test is reading ‘ready’)… Called the Hyundai Dealer and they said try idling the car first thing in the morning for 20 minutes… no change. Garage that did the plugs suggested doing the O2 sensors for 1K… so I put 4 new O2 sensors in myself for 200… put on 500 additional miles but still those 2 tests will not complete. My inspection is up at the end of December and I don’t know what to do. Hyundai dealer says to keep driving it that eventually it will throw a code or the tests will complete but I am running out of time (and they can’t tell me what the normal drive cycle mileage is. PA emissions test can run with one 1 incomplete diagnostic test but not 2 and I really can’t afford to go out and buy a car and a get car payment right now (esp after putting 1500 into it since October). My baby is in good shape otherwise… I just can’t get her inspected like this - AUTO FAILURE if I try.

Does anyone have any suggestions other than keep driving it and at some point maybe something will happen? It got over 125 drive cycles on it since the new plugs and 1500 miles… highway and city (including down and back to DC which is 130 miles each way) … even TRIED to do the OBD drive cycle and was almost run off the road based on those stupid specs of letting it coast to 0mph from 60!.. something is not right…it can’t be.
Thank you!!!

It would have finished the drive cycle by now. Did you install aftermarket O2 sensors? They could be the problem. Have you disconnected the battery for 30 minutes and try reading the codes? If not that’s what I would do.


If he disconnects the battery, all the monitors will be incomplete again

From what I remember, the cat monitor won’t run until the oxygen sensor monitor is complete

Sounds like a catch 22 situation to me, at the moment

4 oxygen sensors for 200 bucks sure sounds like aftermarket parts to me . . .

There’s something I just though of . . . if OP hooks up the code reader again, he might check for pending codes. I don’t know if tool is capable of that, however

Yes, I know it will clear the codes. I thought if it started over it may be able to complete. Sort of like rebooting it. It may show a pending code with a better reader. I’m still thinking it’s aftermarket o2’s causing the non completion code.

First make sure the 15 amp oxygen sensor heater fuse isn’t blown.

Here’s how to reset the both O2 sensors and catalyst monitors.

!. Connect the scan tool.

2.Turn the ignition switch on.

3.MIL must be off.

4.The engine coolant temp and the intake air temp must 41 degrees or greater.

  1. The engine coolant temp and the intake air temp must be be within 10 degrees of each other.

  2. Do not turn the ignition switch off.

  3. Fuel tank level must be at 1/2-3/4 full but 3/4 full is most desirable.

  4. Start the engine and allow it to idle for five minutes with both the air conditioning and rear defogger ON.

9.Turn OFF the air conditioning and rear defogger and allow the engine to idle until the coolant
temp is at 170 degrees or greater

  1. Begin to drive the vehicle with smooth acceleration until 56 MPH is reached.

  2. Release the accelerator for ten seconds or more.

  3. Accelerate again until 56 MPH is reached and drive for 10 minutes at 53-60 MPH.

  4. Slowly decrease the vehicle speed to 0 MPH by applying the brakes.

  5. Allow the engine to idle for one minute.

  6. Accelerate smoothly to 30-35 MPH and drive at 30-35 MPH for five minutes.

  7. Slowly decrease the vehicle speed to 0 MPH by applying the brakes and allow the engine to idle for 45 seconds.

  8. Drive the vehicle at 56-60 MPH for five minutes at steady throttle.

  9. Coast the vehicle to stop WITHOUT applying the brakes.

  10. Allow the engine to idle for 45 seconds.


Hyundai is notorious for the monitors not completing. The drive cycle has to be followed exactly and sometimes then the monitor does not complete. Do not disconnect the battery or clear codes that will reset all the monitors. Does your state have a referee that can inspect the vehicle? Some states have programs that will grant you registration when a car can not be made to pass.

This is one of the many reasons that I’m glad I don’t live in an inspection state. +1 for @SteveC76 on this topic.

You had better take along a co-pilot to read all these instructions to you as you drive.

What a “check list” !!!


You live in PA? You can get an “exemption” from the test, even if it doesn’t pass, provided you spend $150.

In the South Central Region, waivers can only be issued to 1996 and newer vehicles.
The waiver requirements are that a vehicle has failed two OBD Checks and made a
minimum of $150.00 worth of emissions related repairs that address the problem; if these criteria have been met a waiver may be issued.

So, you could show auto store receipts showing you spent $150 on O2 sensors…with FAIL tests before and after…and you’d get stickered anyways! (Then, I suppose somebody could return the unused O2 sensors for a refund…but that would be wrong!)

I live in Allegheny county (with testing required); adjacent Butler county requires no tests. I could legally set up a residence in another county for my car if need be (legally); or (illegally) open a Mail Boxes Etcetra account.

Also note that PA automatically exempts cars driven <5,000 miles. I could (legally) drive an offending car 4,999 miles every year, or (illegally)…

Get the picture?

PA is a state that really doesn’t want testing…but that has been sued in court for failure to adhere to Clean Air standards and has (grudgingly) adopted a testing program…meaning that nobody really cares all that much, or spends much tax money making life miserable for scofflaws.

I’m wondering if you scan tool’s interaction with the ECM is somehow confusing the car’s ECM, and simply connecting the scan tool is what is causing the two tests not to complete properly; i.e. you are inadvertently causing the problem by checking the codes with your scan tool.

If I had this problem I’d clear everything out by disconnecting the battery, then following Tester’s routine above, and refrain from connecting the scan tool.

P.S. If it isn’t too late, retain the old O2 sensors. Oft times the aftermarket replacements aren’t as good as the original. Disregard this if you used OEM versions as replacements.