Trans seems to downshift often and early - Page 2 - JeepForum.com
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post #16 of 26 Old 06-19-2021, 06:26 PM
jtec
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Having reread this thread - I have not seen mention of SCANNING for codes, have you?
As mentioned the TPS is a major input for trans shifting, the MAP is also a input for shifting.

Also the vehicle (powertrain*) is STOCK?


*just tires are changed.


When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #17 of 26 Old 06-20-2021, 09:30 AM Thread Starter
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Quote:
Originally Posted by jtec View Post
Having reread this thread - I have not seen mention of SCANNING for codes, have you?
As mentioned the TPS is a major input for trans shifting, the MAP is also a input for shifting.

Also the vehicle (powertrain*) is STOCK?


*just tires are changed.

Scanned when we got it and then recently. No codes.

No alteration that I am aware of.

The specs I see online for the TPS vary greatly depending on trans, year and poster. I was thinking about replacing the TPS for the heck of it. At this point I don't know what else there is to do aside from monkeying around with the TV cable in tiny amounts.
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post #18 of 26 Old 06-20-2021, 07:22 PM
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CJ7-Tim has some concerns about the TPS - that would be reason enough for me to change it, finding specs, time to test, vs just R&R.

That and maybe loosening up the TV cable a little seams like a plan.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #19 of 26 Old 06-21-2021, 06:31 AM
CJ7-Tim
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I looked up the TPS test specs in my 2000 Factory Service Manual that has genuine Jeep Mechanic coffee and oil stains and it only has a slight variance of the WOT reading:

Quote:
approximate range of .26 volts at minimum throttle opening (idle), to 4.49 volts at wide open throttle.

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not to overthrow the Constitution but to overthrow the men who would pervert the Constitution” Abraham Lincoln, 1859.
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post #20 of 26 Old 06-22-2021, 10:41 AM Thread Starter
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TPS ought to be here in a few days. Will let you know what happens. Worth the $70 to get a genuine one and be sure. Meanwhile I will fiddle with the TV cable. Thanks very much for the assistance.
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post #21 of 26 Old 06-29-2021, 06:05 PM Thread Starter
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Where to start?? Nothing is simple. The XJ seems to shift much better now. I adjusted the TV cable while I was waiting for the new TPS and that helped. Changing the TPS helped also. On the way home I was able to get a little bit of acceleration without the trans kicking down but it did kick down when needed. It also shifted properly when floored and run up to 75. I am happy with that. Now here is something that cropped up a couple of days ago. The CL Light came on when I changed the TPS. My OBDII reader did not see any fault nor did it erase because it did not see a fault. I went to parts store and used their reader which said that three faults were stored in memory. There was the large evap system leak that I thought I fixed and cleared last week. A P0443 Purge control valve and a P0445 TPS high output. I successfully cleared them and they did not return so far. Could these be left over from the earlier troubles. If they do not return I'll be set. Looks like I need a better scanner.
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post #22 of 26 Old 06-29-2021, 06:39 PM
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Are you sure about that P0445 code?
IIRC P044x codes would be EVAP system.

I am willing to bet on CJ7-Tim hunch that TPS was the issue.
ANYWAY glad its shifting better, keep us posted on any new codes or issues.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #23 of 26 Old 06-30-2021, 11:40 AM Thread Starter
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Quote:
Originally Posted by jtec View Post
Are you sure about that P0445 code?
IIRC P044x codes would be EVAP system.

I am willing to bet on CJ7-Tim hunch that TPS was the issue.
ANYWAY glad its shifting better, keep us posted on any new codes or issues.
My mistake. I had a Po445 and a P0443 both are for the evap system that I fixed a week or more ago and cleared. I think mu cheap reader might have not cleared them fully and that they were leftover.
The TPS High Output is a P0123 and it cleared with the better reader at the O'Rileys. I hope it is a leftover from the old one or possibly something I did while testing the old one and I won't even worry unless it comes up again.
I think I am good to go and very much appreciate the help. I am learning.
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post #24 of 26 Old 06-30-2021, 04:21 PM
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I always re-boot the PCM when I install a new OBD engine sensor. This is not required, but it does clear out any old and/or faulty data from a malfunctioning sensor.


This procedure will erase the 1996+ OBD-II "Adaptive Memory" stored inside the PCM and allow a new "Adaptive Memory" to be developed. After performing this procedure the PCM will re-learn and store into Adaptive Memory your engines performance characteristics. Perform these steps exactly as they are written, in the order they are written. This will cause the adaptive memory in the PCM to be erased and cause the PCM to go into Fast Learn adaptive mode.


  • Disconnect the POSITIVE battery Terminal clamp and firmly touch it to ground ( not the battery negative terminal ) for 30 seconds. The engine block or the A/C compressor pump will work as a ground. (This is to discharge the PCM capacitors, which maintain the Adaptive Memory).
  • Reconnect the Battery Cable
  • Turn Ignition Switch to the "ON" position but DO NOT start the engine
  • Turn Headlight "ON"
  • Turn Headlights "OFF"
  • Turn Ignition Key "OFF"
 
The PCM Adaptive memory has now been flashed, or erased from the PCM. When you start the engine it will be running off pre-programmed data tables that come with the PCM from the factory. When the engine gets up to operating temperature the PCM will start to collect and store new data for the Adaptive Memory.

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post #25 of 26 Old 07-01-2021, 12:59 PM Thread Starter
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Thanks. I will do that and save that for next time too. I believe I did reset the PCM when I borrowed the reader from O'Rileys. I can just follow your directions from here on.
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post #26 of 26 Old 07-10-2021, 04:58 PM Thread Starter
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Hi
here is the report:

Shifting is spot on as far as I am concerned. It kicks down if I want but does not do it too easily. The CEL has not returned so it was definitely an old stored code. We have done some long off road drives and a bunch of paved roads getting there and home and no problem at all. Thanks to all.
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