RPM at 2500 while stationed - 97 TJ 4.0 with manual transmission

myjeep3

myjeep3

TJ Enthusiast
Joined
Jul 4, 2019
Messages
490
Location
MA
I had a dead battery yesterday due to leaving the light on. Got a jump from someone, and as soon as the jeep started, the rpm was at 2500 while the gas pedal nor the clutch was pressed.
If I press the clutch, shift and drive, all seem okay until I get to a stop, the rpm will go to 2500. All this start after the dead battery
 
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Try the key trick to see if there are any codes. Not all will cause the CEL to illuminated.

Within five seconds and without starting the engine, turn the ignition on-off-on-off-on.

Leave it on the third time. Any codes will display in the odometer filled by 55 which means end of codes. You will likely get 12 which is battery disconnected recently.

The codes displayed are OBD I two digit codes. Post up any codes you get. If you have any codes you can connect a scanner to the OBD port to get the more detailed OBD II Pcodes.
 
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Verify the throttle blade is fully closing.

Then spay some throttle body cleaner into the idle air bypass hole while it's running to see if the IAC unsticks.

IIRC, when battery power is lost, the PCM runs the IAC fully to one end so that it knows the location. My guess is it ran the IAC fully open and it stuck there.
 
The key trick works just fine to get OBDI codes displayed in my 97 odometer.

It's even described in the 97 FSM..
USING THE VEHICLE ODOMETER
(1) Cycle the ignition key On - Off - On - Off - On
within 5 seconds.
(2) Read the actual DTC number displayed on the
vehicle odometer. Each number will be displayed
with a slight delay between numbers. A DTC code
number 55 will always be the last code to be dis-
played . This will indicate the end of all stored codes.

I also have a Scanguage II connected so generally use that if I want to see if I have any codes due to it displaying the Pcodes.
 
jonny jeep said:
The key trick works just fine to get OBDI codes displayed in my 97 odometer.

It's even described in the 97 FSM..
USING THE VEHICLE ODOMETER
(1) Cycle the ignition key On - Off - On - Off - On
within 5 seconds.
(2) Read the actual DTC number displayed on the
vehicle odometer. Each number will be displayed
with a slight delay between numbers. A DTC code
number 55 will always be the last code to be dis-
played . This will indicate the end of all stored codes.

I also have a Scanguage II connected so generally use that if I want to see if I have any codes due to it displaying the Pcodes.
Click to expand...

Fantastic. Next time I need to read codes I'll turn the key in your jeep, since the trick works on yours. OP should do the same.



Wait that won't work.





He's in MASS & your'e in the UK. Dang, I really thought we had a solution.
 
All seem to be normal again, didn't do anything. I guess the computer relearned, however, the service engine light came on, didn't check yet
 
myjeep3 said:
All seem to be normal again, didn't do anything. I guess the computer relearned, however, the service engine light came on, didn't check yet
Click to expand...

Scanned for codes today and the only code present was P1398 (No crank sensor learned)

Cleared the code..will see if it comes back.
 
hear said:
His build thread is for a 97, I have 2 97's and neither one works with the key trick to read codes.
Click to expand...
The key trick works fine with '97 TJs when done correctly, I had a 97 previously and it worked fine on mine. Only 98-99 TJs don't have the ability to read their own codes. Are you leaving the ignition switch in the On position after the 3rd on-off-cycle long enough to display the codes? The codes don't come up right away. When done properly you'll always at least get a '55' code on a '97.
 
Jerry Bransford said:
The key trick works fine with '97 TJs when done correctly, I had a 97 previously and it worked fine on mine. Only 98-99 TJs don't have the ability to read their own codes. Are you leaving the ignition switch in the On position after the 3rd on-off-cycle long enough to display the codes? The codes don't come up right away. When done properly you'll always at least get a '55' code on a '97.
Click to expand...

Is it the same process as on a 2002? Because it works fine on my 02.

So either I’m too stupid to remember the correct process as I walk across the driveway (but then miraculously remember when I walk the other direction), the process is different on (some?) 97’s, or it doesn’t work on some 97’s.
 
hear said:
Is it the same process as on a 2002? Because it works fine on my 02.

So either I’m too stupid to remember the correct process as I walk across the driveway (but then miraculously remember when I walk the other direction), the process is different on (some?) 97’s, or it doesn’t work on some 97’s.
Click to expand...
The same process works for all years it works on except for 98-99 and, I think, very early '00 TJs. It works on all '97 TJs. Three quick on-off-on turns of the ignition switch completed within five seconds, leaving it in the On position after the third time. 97 TJs only generate two digit codes, not the newer four digit P0123 codes that newer TJs generate.
 
We know this works on early 97s. At some point at or near the changeover to the 98 model year it stopped working. The feature returned somewhere between the 00 and 01 model years.

Maybe your 97s are from later in the production run and have updated PCMs that went on into the 98 model year.

Purely speculation though, as I don't know the production dates for the feature being removed, or returning with the Pcodes displayed for 01-on models
 
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Jerry Bransford said:
The key trick works fine with '97 TJs when done correctly, I had a 97 previously and it worked fine on mine. Only 98-99 TJs don't have the ability to read their own codes. Are you leaving the ignition switch in the On position after the 3rd on-off-cycle long enough to display the codes? The codes don't come up right away. When done properly you'll always at least get a '55' code on a '97.
Click to expand...

If you say so it must be true.

Yes, I understand how to do it, I can do it on my 02 all day long. Both my 97’s just show the odometer. No codes of any sort. Not sure why this is so hard for y’all to believe. The one I just tested on is an early 97.

Everybody in here telling me how it’s supposed to work, I’ve got two counter examples in my driveway. It’s whatever, I don’t care. I know how to read the codes. My only point with even bringing this up was the the OP has a 97 and there exist at least two 97’s that will not read codes in this way, no reason to believe there aren’t others.


Also lol @ “the same process works for all years” except for roughly 30% of the production run.
 
Code P1398 (No crank sensor learned) came back this morning after erasing it yesterday.
 
hear said:
Also lol @ “the same process works for all years” except for roughly 30% of the production run.
Click to expand...
What I actually said was "The same process works for all years it works on except for 98-99 and, I think, very early '00 TJs."

@Wranglerfix Mark can you suggest why this isn't working on his '97? Did it stop working in late '97 TJs?
 
To correct what was stated in the video, 12 is battery input to PCM disconnected within last 50 key on cycles and 55 is completion of fault code display.
 
Code P1398 (No crank sensor learned) came back this morning after erasing it yesterday.
 
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