OBD II "Check Engine" Stories

Hi All,
I find I get to add to my scattered about OBD II stories experiences.

The local high lakes catering fueling station/country store is now off-season selling down their stocks of non-ethanol added gasoline’s. They see a lot to the lakes uses boats trade.
I fill and stock up all of the running vehicles; four-cycle offroad equipment’s and all of my fuel cans this time of the years. Set me up for if-needed 90 days home generator running time.

This year I got to that station with a near empty tank with a fuel light on in the 2007 Hyundai Tuscan. It is E10 rated and that is what it usually gets. From the least expensive source.
This time after filling the three 5 gallon gasoline cans it got ~10 gallons US of pure non-alcohol gasoline.
Within 20 miles and the third cold-to-hot run I set a Check Engine light.
Hmmm? Never had a code set on this vehicle.
It was still running and shifting fine. I’ve been expecting the inaccessible w/o upper engine dissemble, rear, firewall bank of spark plugs at 100K mile to begin misfiring.
This is an old now vehicle with 220,000 miles on it. Transmissions sensor fault? Aged degraded engine sensor fault?

My old 1994 Snap-On red-brick scanner (getting it’s last possible update in 2005) said the code set was because the OBD II catalytic converter monitor test had tripped just past it’s efficiency performance limit set.
Cleared the code.
Filled and topped up with “normal” E10 ethanol gasoline.
Fine now.
No re-occurrence.

This is the fifth time now I have traced back a post 2005 OBD II system “think I have a problem” to simply a user fuel use change. Ultimate corrected with a fuel use change.
Jeep. Ford. Chrysler. Kia. And now this Hyundai.

What are your stories and experiences?

Steve Unruh


Hi All, Actually my latest OBD II story reflects my approach to making my engines run better.
This goes back nearly 50 years now with an obtained 1965 AMC American 2-door. Had a factory compression to he limit inline I-6. Was supposed to be able to run on then leaded regular grade gasoline. Pinged like hell. Retarding the ignition distributor timing 6-4 degrees less than factory did help for that. Lost power. Engine ran hotter.
The real problem was carbons and leads deposits built up onto the valve face heads, the in-head combustion chambers pockets, and the piston tops. Raising the actual compression ratio beyond leaded regular gasoline.
Back-then since the 1930’s it had become known that many engines had to be head-off manually scrap-scarp “de-carbonized” every 30-60K miles. Ha! I’d already done this on a few previously. I did not like all of the grey-lead dust I was creating. The off-shelf available into running engines de-carbonizers did not remove leads deposites. I’d tried hot engine water-spray steaming for an improvement. Still just not good enough.
So this one it was as simple as up-grading to then mid-grade leaded gasoline.
My next AMC I made sure it had a lower ratio rear differential (a station wagon) WITH an overdrive on it’s three speed. Then I could cake-eaters have lower engine loading, and economy top end as I choose.
Look 'Ma. Regular gasoline. No more seasonal pinging.

My lesson from then that I still use today is to modify “cheat” the fuel for existing engines.
And cheat-the-fuels for processes like wood gasification. Woodstove systems.

This is reverse of I Have This Fuel Stock Potential. Now I must design and make from scratch an engine to use this.

My way glorifies the engine/process, user/operator. No need to convince anyone else of anything.
The other direction approach glorifies the best convincing designer. He/she has to convince others to invest in his/her ideas to trial and error get them off the ground. Into production. Into usage acceptance. And once in broad use acceptance then that big-wheel-rolling will resist change. Bite those who try and force change. Crush those who would deviate from the make-them-money existing way.
Ha! Sound familiar!

For two short one-page reads of illustrations Wikipedia up these two articles:
OBD II history
History of alcohol fuels
These will show well it is less about the maths and numbers of thermal-chemical. Mechanical ingenuity’s. And much about the popular social/political and even moral effecting taxation and usage limitations.



Oh. I have said this in the past from decades now of personal experiences.

For the least OBD II created problems search out and favor factory Flex-Fuel vehicles.
They must be materials made to endure up to 85% ethanol fuel mixes.
Have wider range flow injectors.
The computer look-up tables; and PID set trip limits for a much wider range of use applications.
They do not say, or approve this. But these system will tolerate actual methanol, made oxegents like MBTE, and co-solvents containing fuels better too.
Steve Unruh


O.K. My version explaination of OBD II

Electronic fuel injections and stociometric controlling carburetors (feedback) systems did need a computer processor controller. The earliest were analog logic processors. Digital was later.
Theses had no self-diagnostic capability.
System performance problems and it was then gross system inputs/outputs checking. I/O screen checking. Individual sensors checking. Ect.
You had to know the systems characteristics. Have access to conditions sheets of info. Mostly learn from experiences the bugaboo’s of each system type.
A few early analog systems (Toyota and VW/Audi) did begin to be set up for some limited self monitoring and set-limit code tripping.
GM with some of the earliest digital processors went even father on this in the early 1980’s.
Ha! Ha! The late 1970’s and 1980’s were the flash-code/blinking lights prompting era.
All manufactures system by the early 1990’s did have quite a bit of self-testing and shout-out problems capabilities. In assigned numbers; and hexadecimal codes by dedicated code readers then.
Ha! Each manufacturer doing this their own ways. Their own data access plugs. Their own communications protocols. Their own priority and importance assignment for conditions, even worded terminologies.
Remember. STILL all of the system were just to first allow proper fuel for varying conditions. With ignition timing changing by electronics added in then.

It was first the State of California, then the US Federal EPA who asked, then demanded More.
The real changing from these earlier through the early 1990’s systems was the Top-down demand that the engine/trans controller system then be able to be programmed to set up for eight different forced systems on-board testing for “Monitoring” of emissions related systems.
Predict a system failure before it would actually happen.
Sense quickly a degrading/aging system.
Sense immediately a tampered with or damaged system.
Scream like hell - FAILURE!
Get rid of the need for actual vehicle inspections. The delay in getting a gross pee-loot’er ID’ed and repaired. Or shut down from use.
Have the vehicle self-monitor itself. Miraculous results thru modern Digital.
Then as time went on go from simple alerting the driver to:
Shutting off de-powering individual cylinders. Taking away power and transmission gears.
To today being able to be outside of the vehicle be radio wave prompted. Reporting to an authority. So you can be mailed a pee-loot’ers ticket&fine: and demand to then repair and take in for actual compliance inspection.

Still. These OBD II systems having now evolved far past 1996 version “A” systems thru ~2005 “E” systems still do have to do the basic needs of fuel into the engine cylinders. And varying the spark timing now to each individual cylinder.
Basically a telephone that rings when someones calls. You talk. Disconnect. Pay by the call, or monthly use subscription rate.
To phones today . . . .
Far, far past the safety and convenience of now on-person connections is the fact your personal phones know where you are contuiosly; your past uses; your needs & preferences. And can, and do when prompted let others know all of this about you too.

Well guys. So does your very advanced now OBD II vehicles that have connectivity “features”.
My wife’s 2014 Ford Edge.



Ok Steve, I don’t want you to feel all alone in this thread.
This is the current situation:
Daughter’s 2002 Opel Astra refuses to start up in avarage 1 outof 10 times. The starter runs just fine but the engine lacks either sparks or fuel sometimes. Not even a cough. Wait 10 min and try again - if you’re lucky it starts right up. Never anything wrong while it’s running. No idiot light. No codes thrown.
A friend of hers works at an Opel certified garage. He kept and drove the car back and forth to work for whole week. The car refused to start once during that time, but 5 min later with the garage computer hooked up, it cranked right up. Again, no codes.
She was told he could start try swapping gizmos but that it would probably cost her more than the car is worth. His recommendation was to scrap it. It’s a pitty, because apart from not starting, it’s a perfectly good car (I chose it for her 6 years ago).
What could cause the motor to act completly dead from time to time, but nothing wrong most of the time? (Probably a number of reasons)


I have ran into these problems. It is usually a corroded connection, a bad ground, or a wire breaking down. It is time consuming, but can be found. I would go through all the grounds first. Unbolt, and clean


A lot different situation but similar. My old Ford tractor did about the same thing. It turned out to be a short in the wire going threw the distributor to the points. After many hours of ‘‘hunting’’ I called on a friend for help. Together, we spent two afternoons before we hit on the problem. Electrical problems are on and off so hard to tie down. I mention this to remind you not to forget the basics and keep hunting, and hunting. TomC


I had a similar problem as Tom
A stuck carburetor float put some gasoline onto the manifold of my Ford E300 econolin van with a 302 engine.
WHOOSH! Got the fire out quickly with an extinguisher but some wiring damaged.
Fixed everything obvious but still no start.

Eventually found that the heat softened the insulation of the power wire into the distributor allowing it to short = no spark.


Had a real funky-ness in the operation of our OBD II 2000 Honda CRV. The first intermittent problem turned out to be an intermittently bad spark coil. That screwed up the works worse on damp / rainy days. Finally “caught” that one. a couple years later now, had to get the distributor completely new. That solved quite a few problems. Now, needs a new Cadillac converter, can’t get “check engine” light to stay off anymore. 230 thousand miles and not a Cadillac yet! :joy:


Hi Jan-Ola,
All of the advices you have recieved are valid and based on others personal experiences.

The problem though is there is a hell of a lot of wires, connectors and relays IN ADDITION to the PCM (powertrain control module) involved.
The ways you need to approach this:
Quiz her, the shop guy under what exact condition there cranks - no spark - no fuel occurred.
This is a must-know. THEN you can set up to test and diagnosis only under these conditions.
Ambient cold to warm; to underhood hot, changes connector fits. Wound coils as in relays change much too. See?
Only happens after sitting ran and CLOSED HOOD hot soaked? Shhee. Have the hood open cooling just enough that it Never occurs in-shop. Twice this has kicked my ass. GM Cavalier. Toyota FourRunner. Both electronic ignition amplifier’s heat failures.
Both of these after sitting un-running for 20-45 minutes would restart and run fine too. Underhood cooled off just enough!!

EU mandated specs of this vehicle will vary from North America US/Canada/Mexico requirements.
Here after the early 1990’s manufactures were required to have positive fuel and spark shut off system in the event of a running vehicle rollover accident. They wanted electric fuel pumped gasoline NOT to be continued delivered to a wreck damaged hot engine area with electrical sparking capability. That is the system here I would focus on. Be different for a Ford, versus Chrysler, versus GM, etc.
The Chrysler types and imports doing the same I’d be swapping out the seldom used horn relay with the ASD (auto shut-down “SAFETY”) relay.
The PCM power relay if it had an intermittent should have set a code. Same for an intermittent ground on that circuit.
Sometimes (too damn often!) the problem is in the terminals inside a connector body, or worse the power relay center block.
Strong 12 vdc incandescent focused point light, and magnifying glass look over these disconnected in the could-be circuits. This will give you the satisfaction of doing something. And sometimes just the disconnection and re-connection will solve a become poor “fretting” connection problem. Why I had seem swapped out components, solve: then later “come-back” with re-occurrence. Three different new cooling fan relays once into the wife’s minivan until that harness relay plug end was poor 12v terminal connection overheat damaged enough to be readily visible.

Your problem is for sure happening on part of the vehicle NOT PCM monitored.
Do not be afraid to tap, wiggle, twist, jiggle components and wiring harness’s when this is happening. Needs two people. One person to continuously key try: the other to manipulate.
Ford sideways V-6’s due to failed hydro-elastic engine mounts are notorious for within harness breaking down the firewall to engine 64 to 128 wire harnesses. Then weird intermittent’s galore.
90’s Chrysler FWD sedans notorious for across the front chin-curbing and crossover harness damaging.
Dodge 4x4 pickup truck now know for droppped down the transmission harness rub damaing and intermittently to-ground pulling-low the PCM 5 volt circuit killing the spark too. In distibutoe HALL effect sensor is fed off of this circuit too. No Spark detected. PCM then shuts off the fuel injectors.

So see?
The Opel tech was saying well . . . . sometimes it is better to just be happy with the good six years and move on. Hey! She passed the kid-will-wreck-it learning curve! Good for you Dad.
You, me, another grumpy ol’ man stuck might 'cuss, swear, and refuse to give up on an intermittent.
But where a She-in-your-life’s safety is invoked better to buy out of problems and as much as can be afford into safety.
Why I took my wife’s 1999 minivan away at 8 years and drove it myself with accumulating systems failures out to 18 years. Did the same with her 2007 Hyundai after 7 years. Now 5 years into a few problems driving it out to my patience limit. Ha! Endless it seems low loss coolant leaks chasing me. If, when, it ever goes actual headgasket bad . . . . then bye-bye to the scrap yard.


Thanks guys. Lots of good advise there.

Steve, I guess it’s just me. Wanting to evenly wear things down before scrapping. Like the nearby oldtimer walking around with one boot-one shoe, since only one of each were properly worn out.
But I will give things one more try - if time, weather and life allows.


Ha! Ha! Yes I understand. When I wrote this it was with one black merino wool sock and one grey merino wool sock. No longer with mates. Same weights. And I did have 8" high boots on.
More important . . . my wife was away graduating a finished class.
Sigh. I did get caught and busted that evening. My bad memory I’d forgotten my fashion-prefect foe-paw when I un-booted for dinner.

What we can, and must do for ourselves, our sanity, our self-worth is often best set aside for what we must do for others.

Steve Unruh


My daily driver, a 2007 Subaru Forester, that has 273,000 miles as of today, has a “Check Engine” light that used to come on intermittently, and is now on most of the time. When the light comes on, the computer disables the cruise control, which kind of baffles me. I have a Harbor Freight code reader (with reset capability). Resetting only lasts for a few minutes. As near as I can tell, the code means “evaporative emissions leak [small leak]”. It is possible there is a metal line rusted through somewhere. A couple of times when the light went out, the underside of the car could have been plastered (sealed) with snow and ice… Working on it while ignoring and driving on. :laughing:

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Funny, I just had a code like that myself on a Corolla. The gas cap was loose.


I was thinking the same thing about gas cap, they do wear out also.


Rindert, Al,
If it was just the gas cap, that would be great. I could be that lucky! The gas cap seems fine, and it still has a good seal. I think I will have to dig deeper. Rust never sleeps. Nevertheless, I will find a way to seal the filler tube, and see if that helps.

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Hi Mike, if your filler has a leak that would cause the code to come in. I know because I had to replace the filler tube on my Subrau.


Hey everyone. This is not an OBD or check engine light but might come in handy for someone with a “crank no start” Ford. I was driving my Ranger one day had my wife in the back passenger side and my dad in the passenger front seat with his seat moved ahead to give my wife some room. We’re cruising down the road when the engine simply seems to shut off. I’ve been messing with vehicles enough to know it was to quick of a shut off to be mechanical. The engine stall came with no hesitation or sputtering all dummy lights came on. I had done all the usual checks on the side of the road right down to have my dad crank the engine and I tapped the fuel pressure port. It had some pressure and the engine bucked and that was it. I thought fuel filter or fuel pump. I bypassed the fuel pump relay and the pump ran fine checked that the switch was sending power to the relay everything looked fine. Tried it again with the same result as the"side of the road" test. Against my initial thought of the engine shutdown being to quick for it to be anything else but electronic I ordered a filter a replace it. Same as before, I was starting to loose hope. I did more digging in the wiring schematics and something caught my eye. The truck has an inertia switch and the thing is located on the right side of the inner firewall right by the passengers feet. Dad with his seat moved forward had bumped the wires and partially pulled the plug out of the sensor. This now has happened a few times. There’s a relocation kit but now that I know it and we don’t really take that thing anywhere down heavy traffic multi lane highways. Whenever it happens I just lift the carpet on the passenger side and push the plug back in and away we go. There is a holder to keep it plugged in but it’s one of those issues well known to the engineers but not to the rest of human kind :wink: