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Thread: Why does the TPS effect Transmission Shifting.

  1. #1

    Default Why does the TPS effect Transmission Shifting.

    I don't understand how the Throttle Position Sensor effects the Transmission Shifting. I have in-consistant shifting (5.9 46RE) and I read in the search that it might be the TPS!

    I prefer to understand whats going on before I spend the $.

    Any help would be appreciated.
    5.9 Limited LX Slate 45,000 miles

  2. #2
    Registered Jim Hef's Avatar
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    Others will post in here, but the tranny uses electronic solenoids for the shift accuation, and the throttle position may be one of the cues used within the software.

  3. #3
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    What Jim said.

    Plus, I had a problem in my 5.9 that felt like the tranny was slipping in any gear under light load at about 2000 rpm. It felt like it could not hold the gear and would "stumble". This was especially apparent while cruise control was on. I searched the forum and found that the TPS may be bad. Got one from the dealer (I know, I know!), put it in and the problem was gone and has never resurfaced. It's about a 5 minute job.

    BTW: The TPS's from at least 96 and up are all the same part number. The one that they gave me came with instructions for a 99 WJ. It's the exact same part.
    1998 Platinum Jeep Grand Cherokee 5.9 Limited
    Kolak 3" Exhaust, Edelbrock Performer IAS Shocks,
    Silverstars / Kolak Harness,
    K&N drop-in, Fosgate Sound, 15% Tint



  4. #4

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    Thanks Jim and Mike. I'll go out on Monday and buy the TPS.

    Can you remember (Mike) what the part number was. I just want to make sure no mistakes are made, which is possible at my local dealer!!!

    I'll let you know how I get on.
    5.9 Limited LX Slate 45,000 miles

  5. #5
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    Isn't there a way to first test the TPS with a digital voltmeter before running off and buying one???

  6. #6

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    Yes I think it's .7v closed (throttle) and 4.5v fully open. However, my problem is intermittent , so it might seem ok but in-fact be faulty.

    If that's impossible please let me know before Monday!!
    5.9 Limited LX Slate 45,000 miles

  7. #7
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    Actually the JTECH controls shifting by electronically modulating the governor pressure. At least I am pretty sure.
    1998 Limited 5.9

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    MORE TO COME!!!!

  8. #8
    Registered razorbackME's Avatar
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    -=- originally posted by toomanymodz -=-
    Isn't there a way to first test the TPS with a digital voltmeter before running off and buying one???
    Yes. The TPS should give a resistance that changes smoothly over the rotational travel of the sensor. SMOOTH is the key. I usually use a voltmeter reading ohms on the sensor and slowly rotate the part that connects to the throttle (or if it's still on the TB, just move the throttle). The resistance should be very fluid. If it spikes (either up or down), it's toast. You have to rotate it SLOWLY becaus the spikes can be in a really small portion of the sensor.

    This is most easily done with an analog VOM or a digital one that has a graph type readout so you can see it when it jumps. It's really hard to detect on a digital meter that just has a numerical readout.


    The reason the spikes cause problems is that at the location of the spike, the PCM thinks that the throttle has either been shut or opened wide, so it reacts to that.
    98 5.2...Custom TC skid, rock rails, and rear bumper

  9. #9

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    Absolutely right. The most common type of tps malfunction is a"drop out" or "dead spot" as razorbackME describes. A tps is merely a variable resistor much like a reostat (dimmer switch) on a light. The resistor tends to wear out in the spot on the throttle that is most often used (1/4 throttle or so). While the 46RE is not totally dependant on tps signal like most electronically controlled units, it uses the the output speed sensor and tps sensor to create a "mock" governer pressure simulation in addition to the tv cable input to control the 1-2 and 2-3 shifts. The 3-4 shift and converter clutch application are totally dependant on tps, output speed and other sensors. So you can see how tps would effect trans operation. The key is, as razorbackME says, is to rotate it SLOWLY while checking it.
    '88 XJ 4.0L w/ NP242
    Owner, IPT Performance Transmissions

  10. #10
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    -=- originally posted by sammyjacob -=-
    Thanks Jim and Mike. I'll go out on Monday and buy the TPS.

    Can you remember (Mike) what the part number was. I just want to make sure no mistakes are made, which is possible at my local dealer!!!

    I'll let you know how I get on.
    Yep...I actually have the invoice right here. The p/n is 5017479-AA and the description comes up as "SENSOR THROTTLE POSI". Cost me $69.23 with tax for a genuine Mopar sensor. The local Pep Boys, Autozone, etc. didn't stock them. The invoice says clearly, "TPS for 5.9L", but like I said the instructions were for a 99WJ with 4.7L and after comparing the two they were identical.
    1998 Platinum Jeep Grand Cherokee 5.9 Limited
    Kolak 3" Exhaust, Edelbrock Performer IAS Shocks,
    Silverstars / Kolak Harness,
    K&N drop-in, Fosgate Sound, 15% Tint



  11. #11
    Registered razorbackME's Avatar
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    I think the dealer told me that '97 and up was the same sensor, regardless of engine. So I just went to AutoZone and bought one for a 4.0 WJ and it has worked great. The price at AZ was about $35, IIRC.
    98 5.2...Custom TC skid, rock rails, and rear bumper

  12. #12

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    Explain you’re shifting issues on the forum or to me personally and I can let you know the problem... viper1997@earthlink.net

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