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1996 check engine light
10-25-2010, 10:55 PM
Post: #11
RE: 1986 check engine light
(10-20-2010 06:19 PM)Garner Wrote:  What code or codes do you have?

P0122 x 2(T.P.S. Low Voltage)
When I had it diagnosed, I used the diagnostic tool to clear the codes. Without starting the car, or even driving, it still had the same code.(Twice) I have attempted to test the T.P.S., but I can't be positive I'm doing it correctly. I read 5v at the reference terminal, but not too sure how to check for the low voltage. Any ideas?
Also, would a bad signal from the T.P.S. cause the tranny to shift hard?
And, my apologies. It's a 1996 Isuzu Rodeo 3.2Litre, 4W/D.
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10-25-2010, 11:09 PM
Post: #12
RE: 1986 check engine light
Yes, the TPS issue can cause the trany to shift odd because it needs to know the throttle position to work things out via the ECM.

Without a break-out harness you can only 'wing it' but rule of thumb would be reading your 5 volts (to ground) and then probing the other two terminals to see if the volts swing smoothly as the throttle moves full travel. To one terminal it should go from about 0 and move up and to the other it should start near 5 and move down. A full function scanner will be able to read this through the access port under the dash to see if those signals are actually reaching the ECM.

What I'm guessing is the code is from a pinched wire or a bad connection but not sure why you can't clear the code, unless a pinched wire is setting a code as soon as the key is turned on.
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10-26-2010, 03:41 PM
Post: #13
RE: 1986 check engine light
(10-25-2010 11:09 PM)Rupe Wrote:  Yes, the TPS issue can cause the trany to shift odd because it needs to know the throttle position to work things out via the ECM.

Without a break-out harness you can only 'wing it' but rule of thumb would be reading your 5 volts (to ground) and then probing the other two terminals to see if the volts swing smoothly as the throttle moves full travel. To one terminal it should go from about 0 and move up and to the other it should start near 5 and move down. A full function scanner will be able to read this through the access port under the dash to see if those signals are actually reaching the ECM.

What I'm guessing is the code is from a pinched wire or a bad connection but not sure why you can't clear the code, unless a pinched wire is setting a code as soon as the key is turned on.


I can't begin to thank-you enough for all ur input. I still haven't found the problem, but I still have a few places to check out. I'll let u know if or when I finally get it corrected. Thanx again
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10-27-2010, 03:50 AM
Post: #14
RE: 1986 check engine light
(10-23-2010 06:48 PM)Rupe Wrote:  The reason it remains is the code is current so I suggest you back track your work and look for a plug that's not fully seated on the TPS, or perhaps it's just time for a new one. After all the car is 24 years old.

Speaking of old, it's also possible the plug has some crud on it or possibly a broken wire connection due to age / brittle insulation.

Let us know what you find.

Well, here is the latest. My T.P.S. is showing me that it's working properly. After rechecking & back probing, my voltages are accurate & in specs. But I would still feel better if I could get a hold of the diagnostic tool that will show me what the actual voltages are. Because after all is said & done, my C.E.L. is still there. I'm running out of ideas.
but i'm a stubborn ole' cuss, & i'm not giving up.......yet.
I will gladly take any advice that might help.
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10-27-2010, 10:04 AM (This post was last modified: 10-27-2010 10:07 AM by Rupe.)
Post: #15
RE: 1996 check engine light
You sound a bit like me!

What I would do next is go down to a local dealer armed with the VIN and the trouble code. Ask nicely if they can search out any tech bulletins on the issue. Perhaps in the conversation they will say they have seen the problem before and sugest a fix that we have not thought of, although "the fix" may be one of their senior techs spend time with the car on a specialized scanner. It doesn't hurt to ask and I have done that many times for the cost of a box of doughnuts for the advice. Of course in my case I have been running a small fleet here in town for the last 20 years so I already have a relationship with my local dealer but the point is I keep up by brownie points for when I need favors.

BTW, another thing I have learned over the years is a good dealer can be your friend despite the seemingly high posted labor rate. These guys work on the same cars every day and will likely find certain problems in half the time of a small shop.
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10-29-2010, 02:22 PM (This post was last modified: 10-29-2010 02:24 PM by troubled.)
Post: #16
RE: 1986 check engine light
(10-25-2010 10:06 AM)Rupe Wrote:  Yes, I see your point and also can't think of any cars specifically OBDII compliant that early. OTOH, also wondering if there's some cars we really don't get to see, such as high altitude or California only emissions.

That said, we don't have all of the details here either. I know many of the Asian cars of that vintage could not be reset via a battery disconnect. I also know they had a different under-dash plug than the typical US car so scanners were not universal at that point.

Speaking of things not being universal, I wonder if the scanner he's using is an early one with dozens of adaptors and if using the wrong software cartrige is throwing us a curve ball?

The irony here is that aside from some rough shifting, a little high on R.P.M. at start, & the stupid C.E.L., my car is running better than ever!!
Two things I would like some feedback on. I have a feeling the adjustment on the throttle cable might be off a little. Also, the ground wire that's tied into the wiring harness going to the T.P.S, the E.G.R.. & the I.A.C. pulled apart on me while tightening it down, & I had to splice it back together. It looks solid, but how can you tell? Would love to hear what you have to say on this new info.
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10-29-2010, 10:20 PM
Post: #17
RE: 1996 check engine light
Not sure what you mean by the adjustment being off on the throttle cable. As long as there's no extra tension so it can fully close and tight enough so it fully opens you should be fine.

On the ground issue, if in doubt solder the wire together and then make sure the eyelet on the ground bolt is going to bright / clean metal. If in doubt get busy with a wire brish or some sand paper, then coat the connection with some oil or grease to retard corosion before tightening. Lastly, use a multi-meter to verify that ground against the negative battery connection.
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10-30-2010, 12:27 AM
Post: #18
RE: 1996 check engine light
(10-29-2010 10:20 PM)Rupe Wrote:  Not sure what you mean by the adjustment being off on the throttle cable. As long as there's no extra tension so it can fully close and tight enough so it fully opens you should be fine.

On the ground issue, if in doubt solder the wire together and then make sure the eyelet on the ground bolt is going to bright / clean metal. If in doubt get busy with a wire brish or some sand paper, then coat the connection with some oil or grease to retard corosion before tightening. Lastly, use a multi-meter to verify that ground against the negative battery connection.

After taking care of the ground, I will still be showing a C.E.L., won't I?
And I came across the adjustment for the thottle cable at one point, but didn't think that much about it , & now I can't find it anywhere. It did tell me to have someone in the car to depress the pedal while I check the butterfly & make sure that is open to the proper position.(GOD, I hate getting old!!!!) Anyway, other than the dealership, where can I take my car to try & clear out the codes? Autozone can't do it due to liability issues. As always, looking forward to your next input.
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10-30-2010, 11:26 AM
Post: #19
RE: 1996 check engine light
Anybody with a scanner or code reader can clear out the codes. You could probably buy a code reader at Auto Zone that will clear the codes and read any new ones. That could come in handy for future repairs. It could pay for its self if you charged a few bucks to read codes for other people.

Thanks for using the forum,
Garner

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10-30-2010, 11:40 AM
Post: #20
RE: 1996 check engine light
Liability issue? Even in states that do annual testion for emissions there's no question of the codes being cleared because the ECM must go through more than one drive cycle (start cold and fully warmed up) for all functions to read correctly while maintaining the CEL off. IOW, hard to fake it through a test.

Me thinks this guy doesn't know what he's talking about!

That said, a code reader (not a full function scanner) is likely well under $100 and for not much more you can get other features. One trip to a dealer could almost pay for a tool like this.

BTW, being a one man shop I have resorted to using a piece of wood wedged against the seat to hold pedals down when needed. If it's too short then move the seat forward.
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