OBD II - Some Basic Questions

[Dan in Pasadena]

I have an '02 Dodge Ram Quadcab 4x4 which has suddenly shown the check engine light but is running fine*. The * is that I noticed a slight stumble at idle yesterday but it cleared right up and has not returned. This truck has the little 4.7 V8; and though a gas guzzler has been ultra reliable for me.
Truck has 72,xxx miles.

I am wondering about purchasing a plug-in analyzer...which got me thinking. DO I even HAVE OBD-II on this truck? I assume so.

Are the kinds of analyzers you can buy for $100-$200 at the local Pep Boys,Autozone, etc worth a damn? Do they give accurate information? Are they specific as to the information they provide or still leave you to do much diagnosis?

I suppose I should know some of this stuff, but my mechanic training dates to long before on board diagnostic systems.

A link to a thread discussing this or a website would be appreciated too.

[slodave]

Originally Posted by Dan in Pasadena

I am wondering about purchasing a plug-in analyzer...which got me thinking. DO I even HAVE OBD-II on this truck? I assume so.

A quick search, shows that your truck is OBD-2. That's all I can offer.

Dave

[Joeaksa]

Subscribing. Do not know a thing about OBD and guess its time to learn more.

[Dan in Pasadena]

Joe and Dave, You are up late, huh? Me too. You BOTH should have told me "the Search button is your friend, you lazy jerk!"

I did a search and there are pages of posts on this issue. Yes, my truck is OBDII and it looks like there are any number of code readers that also will clear the code. Seems like a lot of positive response to the units offered by Autoengineuity and also, Scantool. BUT of interst to me is a cheapy unit for $39 at Harbor Freight which their website claims will also reset the Check Engine Light (CEL).

I'll check that out. It appears to be a ripoff of an Actron unit I also saw in doing this search. Any other opinions would be appreciated.

By the way, I'm no computer guy so the idea of loading software to my lap top and hooking it up to my truck is'nt all that appealing....I foresee a lot of cussing and calls to my IT-guy nephew!

[slodave]

Originally Posted by Dan in Pasadena

Joe and Dave, You are up late, huh? Me too. You BOTH should have told me "the Search button is your friend, you lazy jerk!"

By the way, I'm no computer guy so the idea of loading software to my lap top and hooking it up to my truck is'nt all that appealing....I foresee a lot of cussing and calls to my IT-guy nephew!

I just copied your year and model into Google and skimmed a few sites.

I don't think you will have too many problems! The software is pretty easy to use.

Dave

[gr8fl4porsche]

No real use clearing the code, it will come back again. Stop by an Autozone and they will read your code for free. Fix the problem, then clear the code.
Good luck.

[NICKG]

Originally Posted by gr8fl4porsche

No real use clearing the code, it will come back again. Stop by an Autozone and they will read your code for free. Fix the problem, then clear the code.
Good luck.

that depends on the code, they can be erroneous . be careful with clearing codes before inspections, as they will fail you for not reaching or setting all the readiness codes

[competentone]

I asked about OBD 2 code readers here a while back; someone mentioned they just had an "Actron OBD II PocketScan" (CP9125) -- it's one of the most basic models, just reads and clears the code.

I got that model and have found it very helpful. It's easier than running to AutoZone -- I think I bought it there though.

[Rick Lee]

I have a reader I got on eBay for around $75 and it's been a great tool. The manual that came with it has a list of a lot of generic codes, which can point you in the right direction if you don't have a list of your vehicle-specific codes. But you can just find it on the Internet somewhere. Clearing your codes can get you through emissions inspection, IF you also have your readiness codes reset and that can be tricky. I'd definitely want a code reader that shows readiness codes. In my own case, I got my readiness codes reset, drove straight to emissions inspection, passed and then the CEL came on a week later. So I did it just in time. My 993 runs like a champ and I have no idea why the computer says the right bank is lean. I just replaced all four O2 sensors (ouch), ran some LubroMoly through and the car runs perfectly.

[lm6y]

Basic code readers / code clearers are fine, but I would recomend one that also shows real - time data streams.

Just because you get a generic code, that doesn't mean that's what's wrong. It is usually just a symptom of the problem. Most people who don't own a scantool think that they are the end all, be all of diagnostic tools. This just isn't so. They are a huge leap forward from a timing light, and a dwell meter though.

Most of your OBD codes are pretty vague, and you still have to use the data the cars computer gives you to fix the problem. It may tell you that you have a misfire on cylinder #1, but it won't tell you why. You use the other sensor data to figure that out.

A captue function is a good thing to have also. It captures data from all of the sensors at the instant you press a button. It's great for finding intermittant problems that won't set a code, but bugs the crap out of you. "Most" OBD2 systems will store all of the sensor data when the code was set also.

Dan, don't shy away from a tool that uses a computer. My scan tool has a PC interfacing program that will let me take the data from the car (whether I capture the data, or it was captured from a code being set), store it in the scan tool, upload the data to my PC, and then chart out what the sensors were doing when the code was set, or I captured the data. I found out why I had a random mis -fire on my Jeep that wouldn't set a code. From the sensor data I saw that it was a lean misfire, and tracked it down to a weak fuel pump. It was quite a bit easier to change at home, than on the side of the road in the middle of the night.

Sorry the post is so long, but it seems a few of you were interested in actual OBD2, hands on experiences.

If you just want to check, and clear codes, your basic units are fine. But if you want to dig a little deeper, dont waste your money, and spend a little more on a unit that does more.

Most of us don't even think about spending good money on good tools. A scan tool IS a tool, and you might as well get a good one.

You have to have a computer to fight a computer after all.

[lm6y]

I forgot to add, make sure your scan tool has CAN (Controller Area Network) capabilities or it wil be obsolete on most things after 2006.

[Rick Lee]

FWIW, after I got the first CEL I took my car to the shop for a full day of diagnostics. They used the Porsche PS or whatever that crazy expensive thing is that looks like an old Etcha-Sketch. While they were able to get the same fault codes, they could find nothing else wrong, other than low voltage in one O2 sensor and actually a rich condition by putting a probe in the tail pipe with the engine off and turning it over by hand. So the lean condition fault code was totally untraceable. Am I right to assume that I'm causing no damage by driving it if it runs and sounds fine? I can't tell if my fuel economy has gotten better because the last entire tank of gas was 100% highway miles and a lot of it in 6th gear or because the LubroMoly cleared out a sticky injector or what exactly happened. My temps run a little high when driving in stop and go traffic on a super hot day. Needle gets to 9 o'clock. But on the hwy. with the a/c on it goes down to about even with the first tick mark.

[Joeaksa]

Originally Posted by Wayne at Pelican Parts

All cars sold in the United States are required by law to be OBD-II compliant for model years 1996 and later. If you use a generic OBD-II scanner, it should tell you what's wrong...

-Wayne

And when did OBD 1 start? Early 90's I am guessing?

Are there any scanners that read the 1 & 2 versions or do I have to buy a scanner for each if I own cars of each era?

[legion]

IIRC, with OBD-I all manufacturers had their own codes, and with OBD-II they went to "standard codes". I think most OBD-I scanners were make-specific. Not that it is impossible to make an OBD-I and OBD-II scanner, I don't know that anyone has done it.

[masraum]

OBDII was mandatory starting in 1997.

I have a ScanGauge 2, www.scangauge.com. It's a great little tool. You can read codes, read the data that the ECU captures for various parameters when it captures a code, reset codes, but then it does a lot more. It's about $160, but it's worth it IMO compared to spending almost as much for a tool that does less.

(they are getting ready to release a FW upgrade that adds several enhancements to the functionality listed below.)

Trip computer
» Maximum Speed
» Average Speed
» Maximum Coolant Temperature
» Maximum RPM
» Driving Time
» Driving Distance
» Fuel Used
» Trip Fuel Economy
» Distance to Empty
» Time to Empty
» Fuel to Empty

Digital Gauges
» Fuel Economy
» Fuel Rate
» Battery Voltage
» Coolant Temperature
» Intake Air Temperature
» Engine Speed (RPM)
» Vehicle speed (MPH)
» Manifold Pressure (not available on some vehicles)
» Engine Load
» Throttle Position
» Ignition Timing
» Open/Closed Loop

Scan Tool
» Reads Trouble Codes
» Reads conditions that set the Trouble Code
» Clears Trouble Codes
» Turns off "Check Engine" light
» Tells you when vehicle is "Ready" to pass OBDII testing
» Make and store up to 10 rewritable special codes to send to the vehicle computer

[lm6y]

Joe, OBD1 started in the 80's. If a car could set a check engine light, or store a code back then, it was OBD1. Legion is dead on, everybody had it, but it was different for all makes. Sometimes it was different from model to model within the same Mfgr!

OBD2 is a standardization protocol. All vehicles sold in the U.S. had to conform to that protocol.

Most of the real scan tools (not just scanners, there is a difference) will do OBD1, but it is car Mfgr specific. So each car Mfgr has a special interface cable for the scan tool.

I plan on replacing my old one with this one soon:
http://www.autoxray.com/product_detail.php?pid=94

The one I have now is so old, they don't list it on the site any longer.

Just in case everyone doesn't know, OBD stands for On Board Diagnostic.

Rick: There is a reason that O2 sensor is reading lean. Might be a bad sensor, might be an intake gasket leaking, might be a clogged injector, leaking fuel rail, bad wiring harness, or a whole slew of other things. The problem could even be on the other bank of cylinders, and the ECM is trying to cut the fuel back to keep the other side in check. See what I mean by being able to look at all the other sensor data? If you can "see" what the computer "sees" you can usually tell what it is trying to do. It's just a computer, and a "dumb" one at that. It's just REALLY fast. It has a set of "maps" in it, and if the data goes off the map, it throws out the Check Engine Light. It doesn't care why that sensor went off the map, just that it did.

If the car wasn't running, and they turned it over by hand and it showed a rich reading, it sounds like you have a leaky injector. Unless the ECM is telling an injector to fire, it should be closed, and not leaking any fuel into the intake port to give you a rich reading. Injectors are set up so that fuel pressure helps close them ( they open AGAINST fuel flow).

Of course it's hard to diagnose a car in Va. when I'm in Il.

Once again sorry for all of the words, I'll shut up now that I've put more than my 2 cents in!

[Rick Lee]

Thanks. Injectors will go in for a rebuild soon. I just hope I'm not damaging anything.

[lm6y]

Rick, don't have them rebuilt on my diagnosis, that may not be the problem. Like I said, you are in Va., and I'm in Il.

Try a bottle of techron (20 oz) to half a tank of fuel, and then some spirited driving to try to clean the injectors out first, and see if that makes a difference. Most of the time that will clean the gunk out.

Most of the time, they just clean an injector really good, and call it a rebuild. It's just like a needle and seat in a carburetor, but it's controlled by electricity, rather than by a float.

If you haven't read this:http://www.amazon.com/dp/0837603005/ref=nosim/?tag=dealtime-books-20&creative=380333&creativeASIN=0837603005&linkCode=asn , I HIGHLY recomend it. After all , all the data in the world means nothing, if you don't know how to interpret it.

[Porsche_monkey]

http://www.obdscan.net/APEX.htm

I have this. It runs on a company laptop. Seems to work with all cars.

As for 'fixing' CEL codes. A forum (vehicle specific) like this one can save a lot of guess work. Cars tend to have common problems that can be solved remotely.

[Dan in Pasadena]

Whew, I went to bed at 1:00a.m. and had a busy day. Didn't get back to my thread until now and there have been a lot of responses. First, thanks everyone.

I have a stupid idea, here it is: I noticed that my truck has a plastic top tank separate from the radiator and that some of the coolant has leaked out and dried on top of the tank. It occurs to me that may be the radiator cap pressure spring has gone soft and that this could cause the check engine light? Preposterous, or remotely possible? I agree that rather than guessing I should get it checked. Since Autozone offers to check it I will start there but also I am in agreement with all, especially IM6Y when he writes,

"A capture function is a good thing to have also. It captures data from all of the sensors at the instant you press a button. It's great for finding intermittant problems that won't set a code, but bugs the crap out of you. "Most" OBD2 systems will store all of the sensor data when the code was set also."

So I will look more seriously at buying an OBDII unit that uses my computer. Reason: I have twice had this truck refuse to shift into first gear after a sustained (hours) run at freeway speed towing my jetski trailer with two skis. Took it to the dealer the first two times (still under warranty then) and they reported they couldn't duplicate the problem and the computer had recorded no codes....leaving them not knowing what to do I suppose. After shutting off the truck and restarting the problem has disappeared - buggingthe crap outta me! This needs to be investigated before I need to rebuild the trans or something! I'll post after I get the Autozone reading. Thanks everyone, Dan